Patent Application
20110175594
I. Field of the Invention
The present invention provides an apparatus for measuring the magnitude of an electric field.
II. Description of Related Art
There are many situations where it is desirable to measure the magnitude or power of an electric field in a particular area. For example, in hybrid automotive vehicles and electric automotive vehicles, the power of the electric field within the power inverter housing for the vehicle is generally quite high. Furthermore, excessive electric fields within the power inverter housing may interfere with other functions of the automotive vehicle, such as radio reception and the like.
There have, however, been previously known devices for measuring the strength or power of an electric field. These previously known devices typically comprise a probe which is placed within the area of interest. The probe is then electrically connected through a cable to an electric field measuring circuit which is removed from the test area.
One disadvantage of these previously known devices, however, is that the electric field of interest is often contained within a closed enclosure, such as the housing for a power inverter of a hybrid or electric vehicle. Consequently, in order to electrically connect the probe to the electric field measuring circuitry, it is necessary to either drill holes through the enclosure through which the antenna cable extends, or to leave the enclosure lid at least partly open so that the antenna probe cable extends between the lid and the enclosure.
In each case, i.e. drilling holes through the enclosure for the antenna probe cable or leaving the enclosure partly open, changes the actual electric field distribution within the enclosure. Consequently, inaccurate readings of the electric field within the enclosure can result.
The present invention provides an apparatus for measuring the magnitude of an electric field which overcomes the above-mentioned disadvantages of the previously known devices.
In brief, the device of the present invention comprises an antenna having an output which is connected to a data converter. The data converter then generates an output signal which is proportional to the magnitude of the electric field detected by the antenna. The output from the data converter is then coupled to a memory unit which stores the magnitude of the electric field.
Unlike the previously known devices, however, the data converter and memory unit are self-contained within a housing and the antenna protrudes outwardly from that housing. Consequently, in order to measure the electric field within an enclosure, such as an enclosure for the power inverter for a hybrid or electric vehicle, the entire apparatus of the present invention is positioned within the desired location within the enclosure and the enclosure is then closed or secured together in its normal fashion. As such, the apparatus of the present invention completely eliminates the previously known requirement of drilling holes within the enclosure and/or leaving the enclosure partly open which may affect the electric field distribution.
After the inverter or other circuitry within the enclosure is operated in the desired fashion, the housing for the apparatus of the present invention is simply removed from the enclosure and the data stored on the memory unit is downloaded or read in any conventional fashion.
Optionally, the apparatus of the present invention contains a display device, also contained within the housing, which displays the magnitude of the electric field. In that event, typically the display device will display the maximum measured power for the electric field during the electric field measuring test run.
A better understanding of the present invention will be had upon reference to the following detailed description when read in conjunction with the accompanying drawing, wherein like reference characters refer to like parts throughout the several views, and in which:
With reference first to
The housing 22 includes a main body 24 as well as a lid 26. With the lid 26 attached across the top of the main body 24, an interior cavity 28 is formed between the lid 26 and the housing main body 24.
A printed circuit board 30 is positioned within the cavity 28 of the housing 22. Electronic components 34, which will subsequently be described in greater detail, are mounted to the printed circuit board 30 in the conventional fashion.
Still referring to
With reference now to
The output 46 from the data converter 44 is coupled as an input signal to digital memory 48. In most cases, the maximum or highest electric field detected by the antenna 40 is desired for engineering design purposes. In that event, the data stored by the memory 48 will store the maximum electric field detected by the antenna 40 during the test run. Alternatively, however, the data converter 44 may be programmed to store a plurality of electric field measurements during sequential time increments during the test run.
Still referring to
It will be understood, however, that the display or data output circuit 52 is optional, in which case the data is merely is merely stored on the memory 48. Following the test run, the data from the memory 48 may be downloaded using any other conventional equipment.
The data converter 44, memory 48 and, if present, the display or data output 52 are all mounted on the printed circuit board 22. As previously described, the antenna 40 comprises a foil line or pattern on the printed circuit board 28. Additionally, a battery 54 is also electrically contained in the housing 22 and connected to the printed circuit board 28 and provides power to the data converter 44, memory 48 and display or data output 52.
With reference now to
There are several advantages to using plural antennas 56 rather than a single antenna 56. For example, the use of plural antennas 56 allows the antennas 56 to be oriented in different directions so that the magnitude or power of the electric field along different axes may be measured. Similarly, the use of plural antennas 56 allows different antennas to be tuned for different frequency ranges. Similarly, different types of antennas may be used, such as monopoles, dipoles, patterns, patch, and the like.
In the event that multiple antennas 56 are employed with the device of the present invention, the data converter 44 preferably comprises a PIC (peripheral interface controller) for selecting which of the multiple antennas 56 for measurement and storage in the memory 48. Such PICs may also include an analog/digital converter to provide a digital output signal to the memory 48 of the magnitude of the electric field.
With reference now to
With reference now to
The power detector 72 forms the data converter and generates an analog output signal on its output 76 that is proportional to the power of the electric field detected by the antenna 40. That output signal is coupled to a peripheral interface controller 76 which includes both an analog-to-digital converter as well as memory. Consequently, the PIC 76 together with the power detector 72 perform the equivalent functions of the data converter 44 and memory 48 (
Still referring to
The PIC 76 also includes a data output line 84 which, once active, provides a digital series output signal on its output 86. This output 86 is then connected to a computer or other device for downloading the data from the PIC 76.
An input 88 on the PIC 76 controls the initiation of the data output from the PIC 76 to its output 86. Momentary depression of a switch 90 momentarily grounds the trigger input 92 of the PIC 76 and initiates the data transfer from the PIC 76 to its output 86.
In many cases, it is only necessary that the memory record the highest electric field detected by the antenna, i.e. the peak for the electric field during the test run. However, in other cases, it would be desirable to record the RF energy at predetermined time increments during a test period.
With reference then to
The timer or trigger 100, which includes an internal clock, may record continuously after power up in predetermined time increments. Conversely, the apparatus may record the sensed magnitudes of the RF power in predetermined increments of time following an external trigger. For example, the trigger may become active only after an electric field in excess of a predetermined minimum is detected. That, furthermore, would be particularly advantageous since a device could be inserted into the desired area for the RF power measurements but would not begin to record the RF power until after the test period had begun.
From the foregoing, it can be seen that the present invention provides a simple and highly effective self-contained apparatus for measuring RF power. Having described our invention, however, many modifications thereto will become apparent to those skilled in the art to which it pertains without deviation from the spirit of the invention as defined by the scope of the appended claims.
