OUTPUT DEVICE FOR HEAT FLOW SENSOR AND OUTPUT METHOD FOR HEAT FLOW SENSOR

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority benefit of Japan Patent Application No. 2017-226961, filed on Nov. 27, 2017. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification.

BACKGROUND
Technical Field

The disclosure relates to an output device for a heat flow sensor and an output method for a heat flow sensor.

Description of Related Art

In recent years, as a device for correcting sensor output data, a device including an offset circuit configured to receive output data from a sensor that receives light and outputs image data and perform offset correction, a gain correction circuit configured to perform gain correction by multiplying output data by a gain correction coefficient, and a gain correction coefficient calculation circuit configured to correct a gain correction coefficient and feed it back to the gain correction circuit has become known (refer to Patent Document 1: Japanese Laid-open No. 2012-2680). In this correction device, when offset correction and gain correction are performed, change in an output level of a sensor due to change in a light intensity over time or change in sensitivity of a sensor over time is corrected.

Here, since an output value of a heat flow sensor tends to change (drift) due to change over time, it is necessary to correct an output value of the heat flow sensor to a reference value, for example, zero (hereinafter referred to as a “reference value correction”). On the other hand, in a device that uses an output value of a heat flow sensor, a wide dynamic range of the output value may be required for the heat flow sensor.

However, as in Patent Document 1, in a configuration in which a preset offset correction coefficient which is an offset correction coefficient input from the outside is applied to output data of a sensor and the data is offset, since a single offset correction coefficient is applied to output data in a wide dynamic range, it is difficult to perform reference value correction of the output data of the sensor.

SUMMARY

An output device for a heat flow sensor according to an embodiment of the disclosure includes an offset value calculation part configured to calculate an offset value for each gain magnification regarding a plurality of gain magnifications; an amplification part configured to amplify an output value of a heat flow sensor by a first gain magnification among the plurality of gain magnifications; an offset part configured to subtract the offset value corresponding to the first gain magnification from the amplified output value; and an A/D converter configured to convert the output value after subtraction thereof into a digital value.

In addition, a output device for a heat flow sensor according to another embodiment of the disclosure includes a step of calculating, using an offset value calculation part, an offset value for each gain magnification regarding a plurality of gain magnifications; a step of amplifying, using an amplification part, an output value of a heat flow sensor by a first gain magnification among the plurality of gain magnifications; a step of subtracting, using an offset part, the offset value corresponding to the first gain magnification from the amplified output value; and a step of converting, using an A/D converter, the output value after subtraction thereof into a digital value.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram exemplifying a schematic configuration of an output device for a heat flow sensor according to an embodiment.

FIG. 2 is a graph exemplifying a relationship between a voltage value of a heat flow sensor and a digital value.

FIG. 3 is a flowchart exemplifying general operations of an output device for a heat flow sensor.

FIG. 4 is a flowchart exemplifying an offset value update process shown in FIG. 3.

FIG. 5 is a flowchart exemplifying a gain magnification change process shown in FIG. 3.

FIG. 6 is a flowchart exemplifying a display process shown in FIG. 3.

DESCRIPTION OF THE EMBODIMENTS

Here, the embodiments of the disclosure provide an output device for a heat flow sensor and an output method for a heat flow sensor through which it is possible to widen a dynamic range of an output value of a heat flow sensor and perform reference value correction of the output value of the heat flow sensor.

According to this embodiment, the output value of the heat flow sensor is amplified by the first gain magnification among the plurality of gain magnifications. Therefore, when the magnification of the plurality of gain magnifications is set to be wide, it is possible to widen a dynamic range of the output value of the heat flow sensor. In addition, an offset value is calculated for each gain magnification and an offset value corresponding to the first gain magnification is subtracted from the amplified output value. Therefore, even if the first gain magnification selected from among the plurality of gain magnifications is changed, when an offset value corresponding to the first gain magnification is subtracted, it is possible to perform reference value correction of the output value of the heat flow sensor. Accordingly, it is possible to widen a dynamic range of the output value of the heat flow sensor and perform reference value correction of the output value of the heat flow sensor.

In the above embodiment, the offset value calculation part may update an offset value corresponding to the first gain magnification based on an average value of n (n is an integer of 2 or more) digital values.

According to this embodiment, an offset value corresponding to the first gain magnification is updated based on the average value of n digital values. In this manner, based on the average value obtained by smoothing n digital values which are time series data in a predetermined period, it is possible to perform update to an offset value suitable for reference value correction of the output value of the heat flow sensor.

In the above embodiment, the average value may be a moving average value of the latest n digital values.

According to this embodiment, an offset value corresponding to the first gain magnification is updated based on the moving average value of the latest n digital values. In this manner, based on the moving average value obtained by smoothing n digital values which are the most recent time series data in a predetermined period, it is possible to perform update to an offset value more suitable for reference value correction of the output value of the heat flow sensor.

In the above embodiment, the output device for a heat flow sensor may further include a gain magnification changing part configured to change the first gain magnification to a second gain magnification among the plurality of gain magnifications based on the digital values.

According to this embodiment, based on the digital values, the first gain magnification is changed to the second gain magnification among the plurality of gain magnifications. In this manner, when the gain magnification is changed from the first gain magnification to the second gain magnification, it is possible to set a gain magnification corresponding to an output value of the heat flow sensor from among the plurality of gain magnifications. Accordingly, it is possible to improve detection performance of the heat flow sensor.

In the above embodiment, when a maximum value of the plurality of digital values is less than a lower limit value corresponding to the first gain magnification, the gain magnification changing part may change the gain magnification to the second gain magnification which is a magnification larger than the first gain magnification and closest thereto among the plurality of gain magnifications.

According to this embodiment, when a maximum value of the plurality of digital values is smaller than the lower limit value corresponding to the first gain magnification, the gain magnification is changed to a second gain magnification which is a magnification larger than the first gain magnification and closest thereto among the plurality of gain magnifications. Accordingly, since the gain magnification can be changed to a magnification larger than the current gain magnification by one step (1 step), it is possible to increase the gain magnification stepwise. Accordingly, it is possible to prevent the amplified output values of the heat flow sensor from becoming discontinuous (discrete) by changing the gain magnification.

In the above embodiment, when the digital value is larger than the upper limit value corresponding to the first gain magnification, the gain magnification changing part may change the gain magnification to the second gain magnification which is a magnification smaller than the first gain magnification and closest thereto among the plurality of gain magnifications.

According to this embodiment, when the digital value is larger than the upper limit value corresponding to the first gain magnification, the gain magnification is changed to the second gain magnification which is a magnification smaller than the first gain magnification and closest thereto among the plurality of gain magnifications. Therefore, for example, since the gain magnification can be quickly changed to a smaller magnification by one digital value, it is possible to avoid saturation of the output value of the heat flow sensor. In addition, since the gain magnification can be changed to a smaller magnification than the current gain magnification by one step (1 step), it is possible to reduce the gain magnification stepwise. Accordingly, it is possible to prevent the amplified output values of the heat flow sensor from becoming discontinuous (discrete) by changing the gain magnification.

In the above embodiment, the step of calculating may include updating, using the offset value calculation part, the offset value corresponding to the first gain magnification based on an average value of the n (n is an integer of 2 or more) digital values.

In the above embodiment, the average value may be a moving average value of the latest n digital values.

According to this embodiment, an offset value corresponding to the first gain magnification is calculated based on the moving average value of the latest n digital values. In this manner, based on the moving average value obtained by smoothing n digital values which are the most recent time series data in a predetermined period, it is possible to perform update to an offset value more suitable for reference value correction of the output value of the heat flow sensor.

In the above embodiment, the method may further include a step of changing, using a gain magnification changing part, the first gain magnification to a second gain magnification among the plurality of gain magnifications based on the digital values.

In the above embodiment, the step of changing may include changing, using the gain magnification changing part, the gain magnification to the second gain magnification which is a magnification larger than the first gain magnification and closest thereto among the plurality of gain magnifications when a maximum value of the plurality of digital values is less than a lower limit value corresponding to the first gain magnification.

In the above embodiment, the step of changing includes changing, using the gain magnification changing part, the gain magnification to the second gain magnification which is a magnification smaller than the first gain magnification and closest thereto among the plurality of gain magnifications when the digital value is larger than an upper limit value corresponding to the first gain magnification.

According to the embodiments of the disclosure, it is possible to provide an output device for a heat flow sensor and an output method for a heat flow sensor through which it is possible to widen a dynamic range of an output value of a heat flow sensor and perform reference value correction of the output value of the heat flow sensor.

Exemplary embodiments of the disclosure will be described below with reference to the appended drawings. Here, in the drawings, the same reference numerals indicate the same or similar components.

[Configuration Example]

First, an example of a configuration of an output device for a heat flow sensor according to the present embodiment will be described with reference to FIG. 1. FIG. 1 is a block diagram exemplifying a schematic configuration of an output device for a heat flow sensor 100 according to the present embodiment.

The output device for a heat flow sensor 100 is an output device for a heat flow sensor HS. As shown in FIG. 1, the output device for a heat flow sensor 100 includes an amplification part 10, an offset part 20, an analog-to-digital (A/D) conversion part 30, a control part 40, and a display part 50.

The heat flow sensor HS is configured to detect a heat flow in an object on which detection is to be performed. The heat flow is thermal energy that passes through an object on which detection is to be performed per unit area, and its unit is, for example, [W/m²]. In addition, the heat flow has a direction. For example, when a direction of movement of thermal energy from one surface to another surface of the object on which detection is to be performed is defined as a positive direction, a direction of movement of thermal energy from the other surface to one surface is defined as a negative direction. The heat flow sensor HS has, for example, a plate-like shape, and is provided on the other surface of the object on which detection is to be performed. When a temperature difference between the two surfaces of the heat flow sensor HS is caused due to the heat flow, the heat flow sensor HS converts the temperature difference into an electromotive force, that is, a voltage, and outputs the result. When the direction of the heat flow is a negative direction, a voltage output from the heat flow sensor HS has a negative (−) value.

Here, the heat flow sensor HS that the output device for a heat flow sensor 100 of the present embodiment uses can use any detection principle. The heat flow sensor may be, for example, a sensor that uses a thermoelectric effect (the Seebeck effect), or a sensor that uses a Fourier's law. In addition, the output value of the heat flow sensor is not limited to a voltage value and other values may be used.

A signal of a voltage value output from the heat flow sensor HS is input to the amplification part 10. The amplification part 10 is configured to amplify a voltage value of the heat flow sensor HS by a predetermined magnification gain (hereinafter referred to as a “gain magnification”). Specifically, the amplification part 10 amplifies a voltage value of the heat flow sensor HS by one gain magnification (hereinafter referred to as a “first gain magnification”) among a plurality of gain magnifications. Therefore, when the magnification of the plurality of gain magnifications is set to be wide, it is possible to widen a dynamic range of the output value of the heat flow sensor.

The amplification part 10 is, for example, a variable gain amplifier including a variable resistor and a plurality of operational amplifiers. The amplification part 10 selects the first gain magnification from among the plurality of gain magnifications based on a control signal input from the control part 40.

A signal of the voltage value of the heat flow sensor HS amplified by the amplification part 10 is input to the offset part 20. The offset part 20 is configured to subtract a predetermined offset value from the amplified voltage value of the heat flow sensor HS. Specifically, the offset part 20 subtracts an offset value corresponding to the first gain magnification from the amplified voltage value. Therefore, reference value correction is performed on the voltage value of the heat flow sensor HS.

The offset part 20 includes, for example, a potentiometer. The offset part 20 selects an offset value and a timing at which the offset value is set based on a control signal input from the control part 40.

A signal of the voltage value of the heat flow sensor HS from which the offset value is subtracted by the offset part 20 is input to the A/D converter 30. The A/D converter 30 is configured to convert the subtracted voltage value of the heat flow sensor HS into a digital value. Specifically, a control signal is input from the control part 40 to the A/D converter 30. The A/D converter 30 performs sampling, quantization, and encoding on the signal of the voltage value of the heat flow sensor HS from which the offset value is subtracted at a timing (period) based on the control signal, and converts the voltage value into a digital value. The A/D converter 30 outputs the converted digital value to the control part 40.

Here, in the present embodiment, in the A/D converter 30, the voltage value of the heat flow sensor HS is converted into a digital value using a maximum value in the negative direction as a reference value, for example, zero. Therefore, irrespective of a direction of a heat flow detected by the heat flow sensor HS, all values are converted into a positive digital value. However, the A/D converter 30 may perform digital conversion such that, when the voltage value of the heat flow sensor HS is in the negative direction, it may be converted into a negative value using, for example, two's complement.

The control part 40 is configured to control operations of respective parts of the output device for a heat flow sensor 100. The control part 40 includes, for example, a microprocessor such as a central processing unit (CPU), and a memory such as a read only memory (ROM), a random access memory (RAM), and a buffer memory. The control part 40 includes, for example, an offset value calculation part 41, a gain magnification changing part 42, and a display control part 43 as functional configurations.

The offset value calculation part 41 is configured to calculate an offset value for each gain magnification regarding the plurality of gain magnifications of the amplification part 10. As described above, the offset part 20 subtracts an offset value corresponding to the first gain magnification from the amplified output value. Therefore, even if the first gain magnification selected from among the plurality of gain magnifications is changed, when an offset value corresponding to the first gain magnification is subtracted, it is possible to perform reference value correction of the output value of the heat flow sensor HS.

In addition, the offset value calculation part 41 is configured to update an offset value for each gain magnification based on the digital value converted to by the A/D converter 30. Specifically, the offset value calculation part 41 updates an offset value corresponding to the first gain magnification based on an average value of n (n is an integer of 2 or more) digital values. The updated offset value is output to the offset part 20. In this manner, based on the average value obtained by smoothing n digital values which are time series data in a predetermined period, it is possible to perform update to an offset value suitable for reference value correction of the output value of the heat flow sensor HS.

Specifically, the offset value calculation part 41 stores n digital values input from the A/D converter 30 in, for example, a memory or a buffer, and obtains an average value from these n digital values.

In one or some exemplary embodiments, the average value that the offset value calculation part 41 uses is a moving average value of the latest n digital values. In this manner, based on the moving average value obtained by smoothing n digital values which are the most recent time series data in a predetermined period, it is possible to perform update to an offset value more suitable for reference value correction of the output value of the heat flow sensor HS.

Here, in the following description, for simplicity of explanation, an example in which a simple moving average value is used as a moving average value will be described, but the disclosure is not limited thereto. The moving average value may be, for example, a load moving average value, or an exponential smoothing moving average value.

The gain magnification changing part 42 is configured to change the first gain magnification which is the current gain magnification of the amplification part 10 to another gain magnification (hereinafter referred to as a “second gain magnification”) among the plurality of gain magnifications based on the digital value converted to by the A/D converter 30.

In this manner, when the gain magnification is changed from the first gain magnification to the second gain magnification, it is possible to set a gain magnification corresponding to an output value of the heat flow sensor HS from among the plurality of gain magnifications.

Specifically, the gain magnification changing part 42 stores an upper limit value and a lower limit value for each gain magnification in a memory or the like in advance. In addition, among a plurality of digital values that are amplified by the current first gain magnification by the amplification part 10 and converted to by the A/D converter 30, the maximum value is stored in a buffer or the like.

Here, changing the gain magnification will be described with reference to FIG. 2. FIG. 2 is a graph exemplifying a relationship between a voltage value of the heat flow sensor HS and a digital value. Here, in FIG. 2, the horizontal axis represents a voltage value of the heat flow sensor HS, and the vertical axis is a digital value converted to by the A/D converter 30. In FIG. 2, regarding a voltage value of the heat flow sensor HS, respective digital values amplified by four gain magnifications GM1, GM2, GM3, and GM4 are indicated by solid lines and a digital value amplified by one gain magnification selected from among the four gain magnifications GM1, GM2, GM3, and GM4 are indicated by bold lines. Here, among the four gain magnifications GM1, GM2, GM3, and GM4, the gain magnification GM1 is a minimum magnification, and the gain magnification GM4 is a maximum magnification.

As shown in FIG. 2, an upper limit value UV and a lower limit value LV of a digital value are set for each gain magnification. The upper limit value UV of the digital value is a value smaller than a digital value corresponding to the maximum value that can be displayed on the display part 50. The lower limit value LV of the digital value is a value larger than a digital value corresponding to the minimum value that can be displayed on the display part 50. For example, when the voltage value of the heat flow sensor HS is larger than a voltage value VV1, as indicated by the bold line in FIG. 2, the voltage value of the heat flow sensor HS is amplified by the gain magnification GM1. On the other hand, when the voltage value of the heat flow sensor HS is larger than a voltage value VV2 and is smaller than the voltage value VV1, as indicated by the bold line in FIG. 2, the voltage value of the heat flow sensor HS is amplified by the gain magnification GM2. In this case, while it is possible to amplify a voltage value of the heat flow sensor HS by the gain magnification GM1, since the digital value amplified by the gain magnification GM2 is larger, it is then possible to improve detection performance of the heat flow sensor HS. However, when the voltage value exceeds the voltage value VV1 of the heat flow sensor HS and is amplified by the gain magnification GM2, the digital value exceeds the upper limit value UV of the gain magnification GM2 and there is a risk of saturation. Therefore, the gain magnification GM1 and the gain magnification GM2 are changed using the lower limit value LV of the gain magnification GM1 corresponding to the voltage value VV1 of the heat flow sensor HS and the upper limit value UV of the gain magnification GM2 as boundary values.

Similarly, the gain magnification GM2 and the gain magnification GM3 are changed using the lower limit value LV of the gain magnification GM2 corresponding to the voltage value VV2 of the heat flow sensor HS and the upper limit value UV of the gain magnification GM3 as boundary values. The gain magnification GM3 and the gain magnification GM4 are changed using the lower limit value LV of the gain magnification GM3 corresponding to a voltage value VV3 of the heat flow sensor HS and the upper limit value UV of the gain magnification GM4 as boundary values.

In one or some exemplary embodiments, the upper limit value UV and the lower limit value LV of the digital value of each gain magnification are set based on a magnification of adjacent gain magnifications. For example, when the magnification of the gain magnification GM1 is 1 and the magnification of the gain magnification GM2 is 4, the lower limit value LV of the digital value of the gain magnification GM1 is set to “100” and the upper limit value UV of the digital value of the gain magnification GM2 is set to “400.” In this case, when the gain magnification is changed from the gain magnification GM2 to the gain magnification GM1, since the magnification ratio of 1/4 is equal to the lower limit value LV of the gain magnification GM1/the upper limit value UV (100/400) of the gain magnification GM2 which is a ratio between digital values, displaying is performed on the display part 50 in consideration of a magnification ratio between gain magnifications, and thus even if the gain magnification is changed, the voltage value of the heat flow sensor HS does not become discontinuous.

Here, in FIG. 2, for simplicity of explanation, an example in which the upper limit values UV of the digital values of the gain magnifications GM1, GM2, GM3, and GM4 are the same, and the lower limit values LV of the digital values are the same is shown, but the disclosure is not limited thereto. The upper limit value and the lower limit value of the digital value may be values different for each gain magnification.

Returning to the description in FIG. 1, when a maximum value of the plurality of digital values is smaller than the lower limit value corresponding to the first gain magnification, the gain magnification changing part 42 changes the gain magnification to the second gain magnification which is a magnification larger than the first gain magnification and closest thereto among the plurality of gain magnifications. Accordingly, since the gain magnification can be changed to a magnification larger than the current magnification by one step (1 step), it is possible to increase the gain magnification stepwise. Therefore, it is possible to prevent the amplified output values of the heat flow sensor from becoming discontinuous (discrete) by changing the gain magnification.

In addition, when the digital value is larger than the upper limit value corresponding to the first gain magnification, the gain magnification changing part 42 changes the gain magnification to the second gain magnification which is a magnification smaller than the first gain magnification and closest thereto among the plurality of gain magnifications. Therefore, for example, since the gain magnification can be quickly changed to a smaller magnification by one digital value, it is possible to avoid saturation of the output value of the heat flow sensor HS. In addition, since the gain magnification can be changed to a smaller magnification than the current gain magnification by one step (1 step), it is possible to reduce the gain magnification stepwise. Accordingly, it is possible to prevent the amplified output values of the heat flow sensor from becoming discontinuous (discrete) by changing the gain magnification.

Based on the digital value converted to by the A/D converter 30, the display control part 43 is configured to control display on the display part 50.

The display part 50 is configured to output information. The display part 50 displays, for example, an output value of the heat flow sensor HS, setting details, and the like. The display part 50 includes, for example, a 7-segment display. In addition, the display part 50 may further include, for example, an indicator lamp for notifying of a warning or the like.

While an example shown in FIG. 1 is shown as a configuration of the output device for a heat flow sensor 100 in the present embodiment, the disclosure is not limited thereto. The output device for a heat flow sensor may include, for example, switches and buttons, and may further include an operation part configured to receive information according to an operation performed by a user. In addition, the output device for a heat flow sensor may include an input and output interface for exchanging data and a signal between it and an external device.

[Operation Example]

Next, an example of an operation of the output device for a heat flow sensor 100 according to the present embodiment will be described with reference to FIG. 3 to FIG. 6. FIG. 3 is a flowchart exemplifying a general operation of the output device for a heat flow sensor 100. FIG. 4 is a flowchart exemplifying an offset value update process S210 shown in FIG. 3. FIG. 5 is a flowchart exemplifying a gain magnification change process S230 shown in FIG. 3. FIG. 6 is a flowchart exemplifying a display process S250 shown in FIG. 3.

For example, when a power supply is turned on and activated, the output device for a heat flow sensor 100 performs an output process for a heat flow sensor S200 shown in FIG. 3.

First, the amplification part 10 amplifies the voltage value of the heat flow sensor HS with the first gain magnification (S201). Immediately after the output process for a heat flow sensor S200 starts, for example, the first gain magnification having a maximum magnification among the plurality of gain magnifications is set.

Next, the offset part 20 subtracts an offset value corresponding to the first gain magnification from the amplified voltage value of the heat flow sensor HS (S202).

Next, the A/D converter 30 converts the voltage value of the heat flow sensor HS from which the offset value has been subtracted into a digital value (S203). Therefore, the control part 40 can acquire the digital value of the voltage value of the heat flow sensor HS.

In the following description, in order to distinguish the latest digital value acquired in step S203 from a past digital value, it is specifically expressed as a digital value DV.

Next, the offset value calculation part 41 performs the offset value update process S210 to be described below. In the offset value update process S210, based on an average value of n digital values, an offset value corresponding to the current first gain magnification is updated.

Next, the gain magnification changing part 42 performs the gain magnification change process S230 to be described below. In the gain magnification change process S230, based on the digital value DV acquired in step S203, the first gain magnification is changed to the second gain magnification.

Next, the display control part 43 performs the display process S250 to be described below. In the display process S250, the digital value DV acquired in step S203 is displayed.

After the display process S250, the output device for a heat flow sensor 100 returns to step S201. For example, until the device is stopped by turning the power supply off or the like, the display process S250 is repeated from step S201.

When the offset value update process S210 starts, as shown in FIG. 4, first, the offset value calculation part 41 adds the digital value DV acquired in step S203 shown in FIG. 3 and calculates an offset value sum SOV which is a sum of n digital values (S211). The offset value sum SOV is calculated by the following Formula (1) using, for example, the digital value DV.

SOV=SOV+DV (1)

Here, when the digital value DV acquired in S203 is the (n+1)th digital value, the oldest digital value among the past n digital values is subtracted from the offset value sum SOV. Therefore, the offset value sum SOV for obtaining a moving average value is calculated. In the following description, n is expressed as an offset value average number n.

Next, the offset value calculation part 41 adds “1” to an addition number AN (S212). Here, zero may be preset as an initial value of the addition number AN. In addition, “n” may be preset as the initial value of the addition number AN, and in step S212, the offset value calculation part 41 may subtract “1” from the addition number AN.

Next, the offset value calculation part 41 determines whether the addition number AN is the offset value average number n or more (S213).

When the result of determination in step S213 is that the addition number AN is the offset value average number n or more, the offset value calculation part 41 calculates an offset value OV (S214). The offset value OV is calculated by the following Formula (2) using, for example, a reference value RV.

OV=RV−SOV/n (2)

Here, the reference value RV is a value serving as a reference defined for each gain magnification, and in Formula (2), a reference value corresponding to the current first gain magnification is used.

Next, the offset value calculation part 41 outputs the offset value OV calculated in step S214 to the offset part 20, and updates an offset value corresponding to the current first gain magnification (S215). Then, after step S215, the offset value calculation part 41 terminates the offset value update process S210.

On the other hand, when the result of determination in step S213 is that the addition number AN is smaller than the offset value average number n, the offset value calculation part 41 terminates the offset value update process S210 without doing anything.

When the gain magnification change process S230 starts, as shown in FIG. 5, first, the gain magnification changing part 42 determines whether the digital value DV acquired in S203 shown in FIG. 3 is larger than the upper limit value UV corresponding to the first gain magnification (S231).

When the result of determination in step S231 is that the digital value DV is larger than the upper limit value UV corresponding to the first gain magnification, there is a risk of saturation of the digital value of the voltage value of the heat flow sensor HS amplified by the first gain magnification. Therefore, the gain magnification changing part 42 outputs a control signal to the amplification part 10, and changes the gain magnification to the second gain magnification which is a magnification smaller than the first gain magnification and closest thereto among the plurality of gain magnifications, that is, lowers the gain magnification by one step (1 step) (S232).

An example in which, in step S231, it is determined whether one of the latest digital values DV is larger than the upper limit value UV of the first gain magnification, and when the digital value DV is larger than the upper limit value UV of the first gain magnification, the gain magnification is lowered by one step has been shown in the present embodiment, but the disclosure is not limited thereto. For example, it may be determined whether an average value of the latest k (k is an integer of 2 or more) digital values is larger than the upper limit value UV of the first gain magnification, and when the average value is larger than the upper limit value UV of the first gain magnification, the gain magnification may be lowered by one step.

After step S232, the gain magnification changing part 42 performs a reset process (S233). In the reset process, the gain magnification changing part 42 returns a value depending on the gain magnification to the initial value. For example, the gain magnification changing part 42 sets the offset value sum SOV calculated in step S211 shown in FIG. 4, the addition number AN added in step S212, and a determination number JN and a maximum value MV to be described below to zero.

After step S233, the gain magnification changing part 42 terminates the gain magnification change process S230.

On the other hand, when the result of determination in step S231 is that the digital value DV is equal to or less than the upper limit value UV corresponding to the first gain magnification, the gain magnification changing part 42 adds “1” to the determination number JN (S234). Here, zero is preset as an initial value of the determination number JN. In addition, as an initial value of the determination number JN, a determination necessary number RN to be described below is set, and in step S234, the gain magnification changing part 42 may subtract “1” from the determination number JN.

Next, the gain magnification changing part 42 determines whether the digital value DV is larger than the maximum value MV in the plurality of past digital values (S235).

When the result of determination in step S235 is that the digital value DV is larger than the maximum value MV, the gain magnification changing part 42 updates the maximum value MV to the digital value DV as a new maximum value (S236).

On the other hand, when the result of determination in step S235 is that the digital value DV is equal to or less than the maximum value MV, the gain magnification changing part 42 terminates the gain magnification change process S230.

After step S236, the gain magnification changing part 42 determines whether the determination number JN is equal to or larger than the determination necessary number RN (S237). In the determination necessary number RN, in order to determine whether the gain magnification is raised to a gain magnification having a larger magnification than the first gain magnification, the number of digital values considered to be necessary is preset.

When the result of determination in step S237 is that the determination number JN is equal to or larger than the determination necessary number RN, the gain magnification changing part 42 determines whether the maximum value MV updated in step S236 is smaller than the lower limit value LV corresponding to the first gain magnification (S238).

When the result of determination in step S238 is that the maximum value MV is smaller than the lower limit value LV corresponding to the first gain magnification, if the digital value of the voltage value of the heat flow sensor HS amplified by the first gain magnification is amplified by the second gain magnification having a larger magnification, there is a high probability of the value becoming closer to the upper limit value UV corresponding to the second gain magnification. When the amplified value becomes closer to the upper limit value UV of the gain magnification, it is possible to improve the detection performance of the voltage value of the heat flow sensor HS. Therefore, the gain magnification changing part 42 outputs a control signal to the amplification part 10, and changes the gain magnification to the second gain magnification which is a magnification larger than the first gain magnification and closest thereto among the plurality of gain magnifications, that is, raises the gain magnification by one step (1 step) (S239).

After step S239, the gain magnification changing part 42 performs the reset process in step S233 described above, and then terminates the gain magnification change process S230.

On the other hand, when the result of determination in step S237 is that the determination number JN is smaller than the determination necessary number RN, or when the result of determination in step S238 is that the maximum value MV is equal to or larger than the lower limit value LV corresponding to the first gain magnification, the gain magnification changing part 42 terminates the gain magnification change process S230 without doing anything.

When the display process S250 starts, as shown in FIG. 6, first, the display control part 43 calculates a display value IV based on the latest digital value DV (S251). For example, the display value IV is obtained by multiplying the digital value DV by a predetermined constant.

Next, the display control part 43 adds the display value IV calculated in step S251 and calculates a display determination sum SID which is a sum of m (m is an integer of 2 or more) display values IV (S252). For example, the display determination sum SID is calculated by the following Formula (3) using the display value IV.

SID=SID+IV (3)

Here, when the display value IV calculated in step S251 is the (m+1)th display value IV, the oldest the display value IV among the past m display values IV is subtracted from the display determination sum SID. Therefore, the display determination sum SID for obtaining a moving average value is calculated. In the following description, m is expressed as a display determination value average number m.

Next, the display control part 43 determines whether a display determination average value is equal to or larger than a display lower limit threshold value and is equal to or less than a display upper limit threshold value (S253). The display determination average value is a value (SID/m) obtained by dividing the display determination sum SID by a display determination value average number m. The display lower limit threshold value and the display upper limit threshold are values determined for the display determination average value based on a range of values that can be displayed on the display part 50.

When the result of the determination in step S253 is that the display determination average value is greater than or equal to the display lower limit threshold value and less than or equal to the display upper limit threshold, it considered that the display value IV calculated in step S251 will be able to be displayed on the display part 50. Therefore, the display control part 43 outputs and displays the display value IV calculated in step S251 to and on the display part 50 (S254).

On the other hand, when the result of determination in step S353 is that the display determination average value is less than the display lower limit threshold value or larger than the display upper limit threshold value, it considered that the display value IV calculated in step S251 will not be able to be displayed on the display part 50. Therefore, the display control part 43 outputs a control signal indicating an error to the display part 50 so that the error is displayed (S255).

After step S254 or after step S255, the display control part 43 terminates the display process S250.

As described above, in the present embodiment, the voltage value of the heat flow sensor HS is amplified by the first gain magnification among the plurality of gain magnifications. Therefore, when the magnification of the plurality of gain magnifications is set to be wide, it is possible to widen a dynamic range of the output value of the heat flow sensor. In addition, an offset value is calculated for each gain magnification and an offset value corresponding to the first gain magnification is subtracted from the amplified output value. Therefore, even if the first gain magnification selected from among the plurality of gain magnifications is changed, when an offset value corresponding to the first gain magnification is subtracted, it is possible to perform reference value correction of the output value of the heat flow sensor HS. Accordingly, it is possible to widen a dynamic range of the output value of the heat flow sensor and perform reference value correction of the output value of the heat flow sensor.

The embodiments described above are provided to facilitate understanding of the disclosure, and do not limit the interpretation of the disclosure. Elements included in the embodiments, and their arrangements, materials, conditions, shapes, sizes, and the like are not limited to those exemplified and can be appropriately changed. In addition, components shown in different embodiments can be partially replaced or combined.

APPENDIX

1. An output device for a heat flow sensor (100) including an offset value calculation part (41) configured to calculate an offset value for each gain magnification regarding a plurality of gain magnifications, an amplification part (10) configured to amplify an output value of a heat flow sensor (HS) by a first gain magnification among the plurality of gain magnifications, an offset part (20) configured to subtract the offset value corresponding to the first gain magnification from the amplified output value, and an A/D converter (30) configured to convert the output value after subtraction thereof into a digital value.

7. An output method for a heat flow sensor including

a step of calculating, using an offset value calculation part (41), an offset value for each gain magnification regarding a plurality of gain magnifications;

a step of amplifying, using an amplification part (10), an output value of a heat flow sensor (HS) by a first gain magnification among the plurality of gain magnifications;

a step of subtracting, using an offset part (20), the offset value corresponding to the first gain magnification from the amplified output value; and

a step of converting, using an A/D converter (30), the output value after subtraction thereof into a digital value.

Claims

1. An output device for a heat flow sensor comprising: an offset value calculation part configured to calculate an offset value for each gain magnification regarding a plurality of gain magnifications;an amplification part configured to amplify an output value of the heat flow sensor by a first gain magnification among the plurality of gain magnifications;an offset part configured to subtract the offset value corresponding to the first gain magnification from the amplified output value; andan A/D converter configured to convert the output value after subtraction thereof into a digital value.
2. The output device for the heat flow sensor according to claim 1, wherein the offset value calculation part updates the offset value corresponding to the first gain magnification based on an average value of n (n is an integer of 2 or more) digital values.
3. The output device for the heat flow sensor according to claim 2, wherein the average value is a moving average value of the latest n digital values.
4. The output device for the heat flow sensor according to claim 1, further comprising a gain magnification changing part configured to change the first gain magnification to a second gain magnification among the plurality of gain magnifications based on the digital value.
5. The output device for the heat flow sensor according to claim 2, further comprising a gain magnification changing part configured to change the first gain magnification to a second gain magnification among the plurality of gain magnifications based on the digital value.
6. The output device for the heat flow sensor according to claim 3, further comprising a gain magnification changing part configured to change the first gain magnification to a second gain magnification among the plurality of gain magnifications based on the digital value.
7. The output device for the heat flow sensor according to claim 4, wherein, when a maximum value of a plurality of digital values is less than a lower limit value corresponding to the first gain magnification, the gain magnification changing part changes the first gain magnification to the second gain magnification which is a magnification larger than the first gain magnification and closest thereto among the plurality of gain magnifications.
8. The output device for the heat flow sensor according to claim 5, wherein, when a maximum value of a plurality of digital values is less than a lower limit value corresponding to the first gain magnification, the gain magnification changing part changes the first gain magnification to the second gain magnification which is a magnification larger than the first gain magnification and closest thereto among the plurality of gain magnifications.
9. The output device for the heat flow sensor according to claim 6, wherein, when a maximum value of a plurality of digital values is less than a lower limit value corresponding to the first gain magnification, the gain magnification changing part changes the first gain magnification to the second gain magnification which is a magnification larger than the first gain magnification and closest thereto among the plurality of gain magnifications.
10. The output device for the heat flow sensor according to claim 4, wherein, when the digital value is larger than an upper limit value corresponding to the first gain magnification, the gain magnification changing part changes the first gain magnification to the second gain magnification which is a magnification smaller than the first gain magnification and closest thereto among the plurality of gain magnifications.
11. The output device for the heat flow sensor according to claim 5, wherein, when the digital value is larger than an upper limit value corresponding to the first gain magnification, the gain magnification changing part changes the first gain magnification to the second gain magnification which is a magnification smaller than the first gain magnification and closest thereto among the plurality of gain magnifications.
12. The output device for the heat flow sensor according to claim 6, wherein, when the digital value is larger than an upper limit value corresponding to the first gain magnification, the gain magnification changing part changes the first gain magnification to the second gain magnification which is a magnification smaller than the first gain magnification and closest thereto among the plurality of gain magnifications.
13. The output device for the heat flow sensor according to claim 7, wherein, when the digital value is larger than an upper limit value corresponding to the first gain magnification, the gain magnification changing part changes the first gain magnification to the second gain magnification which is a magnification smaller than the first gain magnification and closest thereto among the plurality of gain magnifications.
14. The output device for the heat flow sensor according to claim 8, wherein, when the digital value is larger than an upper limit value corresponding to the first gain magnification, the gain magnification changing part changes the first gain magnification to the second gain magnification which is a magnification smaller than the first gain magnification and closest thereto among the plurality of gain magnifications.
15. An output method for a heat flow sensor comprising: a step of calculating, using an offset value calculation part, an offset value for each gain magnification regarding a plurality of gain magnifications;a step of amplifying, using an amplification part, an output value of the heat flow sensor by a first gain magnification among the plurality of gain magnifications;a step of subtracting, using an offset part, the offset value corresponding to the first gain magnification from the amplified output value; anda step of converting, using an A/D converter, the output value after subtraction thereof into a digital value.
16. The output method for the heat flow sensor according to claim 15, wherein the step of calculating includes updating, using the offset value calculation part, the offset value corresponding to the first gain magnification based on an average value of n (n is an integer of 2 or more) digital values.
17. The output method for the heat flow sensor according to claim 16, wherein the average value is a moving average value of the latest n digital values.
18. The output method for the heat flow sensor according to claim 15, further comprising a step of changing, using a gain magnification changing part, the first gain magnification to a second gain magnification among the plurality of gain magnifications based on the digital value.
19. The output method for the heat flow sensor according to claim 18, wherein the step of changing includes changing, using the gain magnification changing part, the first gain magnification to the second gain magnification which is a magnification larger than the first gain magnification and closest thereto among the plurality of gain magnifications when a maximum value of a plurality of digital values is less than a lower limit value corresponding to the first gain magnification.
20. The output method for the heat flow sensor according to claim 18, wherein the step of changing includes changing, using the gain magnification changing part, the first gain magnification to the second gain magnification which is a magnification smaller than the first gain magnification and closest thereto among the plurality of gain magnifications when the digital value is larger than an upper limit value corresponding to the first gain magnification.

Priority Claims (1)

Number	Date	Country	Kind
2017-226961	Nov 2017	JP	national

OUTPUT DEVICE FOR HEAT FLOW SENSOR AND OUTPUT METHOD FOR HEAT FLOW SENSOR

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Priority Claims (1)