Under 35 USC §120, this application claims the benefit of priority to CHINA Patent Application No. 200710306310.6, filed Dec. 28, 2007 entitled “A METHOD FOR IMPROVING THE REPCISION AND RELIABILITY OF CIRCUIT HEATING CONTROL THROUGH A 1-WIRE SENSOR”, all of which is incorporated herein by reference.
The present invention relates to a method for improving the precision and reliability of the heating control for an anesthetic machine circuit, which is applicable for the heating control of devices involved in medical diagnosis, and more particularly for the temperature monitoring and control on the circuit heating part in an anesthetic machine or ventilator.
At present, the anesthetic machine circuit is heated by the technical solution in which open-loop control or analog signal closed-loop control is employed. Usually, a heating element with a certain positive temperature factor, such as positive coefficient (PTC), is used to perform the heating. Meanwhile, the heating power is decreased automatically as the temperature is rising such that a certain heating temperature is reached. Such a technical solution has disadvantages of low precision control and poor reliability. Such a heating element has low temperature precision which is typically in the range of ±5 degrees. In a technical solution which uses the analog signal closed-loop control, a temperature sensitive element such as a thermistor is used to monitor and control the temperature, in which the precision is high, however there exist the following disadvantages: the anti-disturbance performance is poor; it requires high signal connection quality; the line compensation needs to be considered; the control circuit itself tends to be influenced by the temperature; the reliability is low; it is difficult to determine the sensor failure; and the overheating occurs easily.
Accordingly, what is needed is a system and method that overcomes the above-identified issues. The present invention addresses such a need.
In order to improve the precision and reliability of the conventional control solution, one aspect of an embodiment provides a method for improving the precision and reliability of the heating control for an anesthetic machine circuit. The method, besides improving the precision and reliability of the heating control of an anesthetic machine circuit, may additionally reduce the requirements on the interfaces of the system, which provides for a long-distance heating control of the system. Another aspect of the embodiment invention provides a heating control system for an anesthetic machine circuit.
To achieve the above objectives, a 1-wire temperature sensor is adopted at the target position of the heating control, i.e., in the anesthetic machine circuit, and performs temperature measurement and control in cooperation with the heating element. With the 1-wire temperature sensor adopted, it is enough to connect temperature signal line, heating power supply output line, ground line (the heating power supply ground line may have the dual purpose as the sensor signal ground line). A microcontroller is used as the control unit. By using program, the sensor verification and the validity recognition are carried out based on 1-wire transmission protocol, and the function of temperature detection is fulfilled. According to certain algorithm such as PID, boundary restriction etc., the microcontroller controls average heating power by controlling the duty cycle of the heating output time, so as to control the temperature.
Depending on the type of the adopted controller, an embodiment may also include functions such as the input/output of data, condition indication, alarm and failure protection through I/O port or communication interface of the controller.
According to one aspect of an embodiment, a method for improving the precision and reliability of the heating control for an anesthetic machine circuit includes the steps of: A 1-wire sensor is positioned in the anesthetic machine circuit and the signals of the 1-wire temperature sensor are transmitted to the control unit; and a control unit processes the signals of the 1-wire temperature sensor so as to control the operation of a heating element.
According to another aspect of the present invention, a heating control system for an anesthetic machine circuit comprises: a control unit electrically connected to a control switch; a heating element used to heating the anesthetic machine circuit and electrically connected to a power supply via the control switch; a 1-wire temperature sensor which is positioned in the circuit and connected to the control unit via a temperature signal line, wherein the control unit receives the signal from the 1-wire temperature sensor and controls the average heating power by controlling the duty cycle of the heating output time.
When using a 1-wire temperature sensor, the precision is relative higher, which solves the problem of the analog signal transmission error. The use of the sensor is facilitated and a long-distance temperature detection and control is performed, and also the digital signal form and the interface protocol of the sensor have relative higher anti-disturbance performance and validity recognition function. Thus the requirements on the interface connection quality is reduced, and the reliability is improved.
It should be noted that the above description and the following detailed explanation is illustrative, which is intended to further describe the claimed invention.
A part from the above mentioned objectives, features and advantages, the present invention has other objectives, features and advantages which are hereinafter further described in details in conjunction with the accompanying drawings.
The figure included for constituting a part of the specification and further explaining the present invention shows the preferable embodiment and serves for describing the principle of the invention along with the description.
The purpose, advantages and features of the present invention will become more apparent by description with reference to the following accompanying drawing.
The present invention relates to a method for improving the precision and reliability of the heating control for an anesthetic machine circuit, which is applicable for the heating control of devices involved in medical diagnosis, and more particularly for the temperature monitoring and control on the circuit heating part in an anesthetic machine or ventilator.
Hereinafter, an embodiment is described in detail in conjunction with the figure.
Sampling program may be designed and realized according to 1-wire bus timing and command protocol (referring to the technical manual for DS18B20, http://www.maxim-ic.com.cn/pdfserv/en/ds/DS18B20.pdf). The temperature control program may employ a PID or a basic boundary restriction algorithm. When requiring heating, the control switch is turned on such that the heating element is powered to perform the heating. Whereas when requiring no heating, the control switch is turned off such that the heating element is powered off to stop the heating. The control programs of the alarm, indication and data communication may be designed as needed.
The basic operation principle and procedure are as follows:
1. The control unit 6 reads ID and verification code of the temperature sensor 1 according to 1-wire protocol and determines the validity of the temperature sensor 1;
2. The control unit 6 reads the temperature value of the temperature sensor 1 and compares it with the target control temperature, and then turns on the control switch 7 when requiring heating such that the power supply 8 powers the heater 2 and the circuit temperature rises, and turns off the control switch 7 when requiring to stop heating such that the heater 2 stops heating and the circuit temperature drops according to the control algorithm. A PWM method is provided in which the average power of the heater is controlled by controlling the heating time per unit time, the circuit B is operated at a predetermined control temperature.
The above is merely the description of the preferable embodiment of the present invention and not used for limiting the present invention. As for those skilled in the art, various changes, variations and omissions can be made to the present invention. Within the spirit and principle of the present invention, any change, substitution or improvement etc. should be covered by the scope of the present invention.
Number | Date | Country | Kind |
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200710306310.6 | Dec 2007 | CN | national |