JPS5931202B2 - AC/DC conversion element for true RMS value measurement - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an AC/DC conversion element suitable for measuring the true effective value of an AC signal.

As a method for measuring the true effective value of an AC signal, for example, the amount of heat generated when an AC signal to be measured is applied to a resistor, and the amount of heat generated when a DC signal is applied to this resistance or a resistor with the same resistance value and shape as this resistance. A method is used in which the true effective value of the AC signal to be measured is determined from the magnitude of the DC signal required to make the calorific value equal to each other.

FIG. 1 is a wiring diagram showing an example of a specific circuit configuration, in which 1 is an input terminal for an AC signal to be measured, 2 is a DC power supply connection terminal, 3 is an output terminal, 4 is an input resistance, and 5 and 6 are A voltage dividing resistor, consisting of resistors with equal resistance values.

T is a differential amplifier, 8 is an output resistor, and 9 and 10 are heating resistors, each of which has the same resistance value.

Thermistors 11 and 12 have the same resistance-temperature characteristics.

The heating resistor 9 and the thermistor 11 are molded as a pair, and the heating resistor 10 and the thermistor 12 are molded as a pair.

When DC voltage is applied to terminal 2, resistor 5 and thermistor 1
The divided voltage at the connection point A of the resistor 6 and the thermistor 12 is equal to each other, but when the AC signal to be measured is applied to the terminal 1, the thermistor 11 is heated by the heating resistor 9, The balance between the divided voltages at points A and B is broken, an output appears in the differential amplifier 7, and this output current is applied to the heating resistor 10 to heat the thermistor 12.

To obtain the true effective value of the AC signal to be measured from the magnitude of the output of the differential amplifier r when the temperature of the thermistor 12 becomes equal to the temperature of the thermistor 11 and the divided voltages at points A and B become equal to each other. I can do it. However, in such a measurement circuit, the heating resistors 9 and 10 and thermistors 11 and 12 are all made up of independent units, and there is a limit to their miniaturization, so there is a limit to improving response and sensitivity. Furthermore, as mentioned above, there is a limit to the miniaturization of the heating resistor and thermistor, so the elements in which these are molded, that is, the AC/DC conversion elements 13 and 14, are also relatively large. In addition, since the distance between the thermistors 11 and 12 is relatively large, the effects of ambient temperature on both heating resistors and both thermistors are different, causing measurement errors.

Furthermore, conventional thermistors have many variations in characteristics and it is difficult to obtain ones with the same characteristics, so measurement errors are inevitable from this point as well.

An object of the present invention is to realize an AC/DC conversion element for true effective value measurement that has good response and sensitivity and can minimize measurement errors.

FIG. 2 is a diagram illustrating an embodiment of the present invention, in which reference numeral 15 denotes a substrate made of single-crystal silicon, the surface of which is formed into a mirror surface and a thin layer of silicon oxide is formed, and the photoetching process is performed using conventionally known photo etching. Multiple sets of identical circuits are formed on the surface of the substrate by techniques and thin film deposition methods described below. Note that the figure shows one set of circuits as a representative, and other circuits are omitted. Furthermore, instead of forming a thin layer of silicon oxide on the surface of the substrate, an insulating layer of tantalum pentoxide, silicon nitride, or the like may be provided on the surface. Next, 16 is a thin film resistor for heating, 1r is its terminal electrode, and tantalum nitride is deposited by sputtering approximately in the area where 16 and 17 are to be formed, or a nickel-chromium alloy is deposited by sputtering or vacuum evaporation, Next, gold, platinum, aluminum, nickel, or the like is deposited thereon by sputtering, vacuum evaporation, plating, or the like, and the heating thin film resistor 16 and terminal electrode 17 of the desired shape are formed by photoetching.

18 is a temperature-sensitive thin film element made of a material with a large temperature coefficient of resistance; 19 is a terminal electrode thereof; gold, platinum, aluminum, nickel, or the like is sputtered, vacuum-deposited, or plated approximately in the area where 18 and 19 are to be formed; etc. to coat it,
The temperature-sensitive thin film element 18 and terminal electrodes 19 of desired shapes are formed by photo-etching.

In this case, the thin film 18 and the electrode 19 were integrally formed using the same material, but the terminal electrode 19 was connected to the lead wire using the same method as that used for forming the heating thin film resistor 16 and its terminal electrode 1r. The temperature-sensitive thin film element 18 may be formed of copper, nickel, or the like, which is suitable for use in gold, platinum, aluminum, nickel, or the like.

Furthermore, instead of forming the temperature-sensitive thin film element 18 using the above-mentioned materials, a thin film thermistor may be deposited by sputtering or vacuum deposition, and in this case, the terminal electrodes are formed from gold, platinum, aluminum, nickel, or the like.

After forming a large number of circuits each consisting of a pair of heating thin film resistors and a temperature sensitive thin film element on a substrate as described above, dicing is performed using, for example, a laser beam, and a lead wire is connected to each terminal electrode. and then molded with a suitable insulating material.

In the device of the present invention configured as described above, since the substrate is made of silicon, it is easy to obtain, and its workability is good, so the surface can be easily formed into a mirror surface.
Therefore, an insulating layer and a thin film can be easily applied to the surface, and dicing can be performed extremely easily and accurately, so it is possible to mold a single heating resistor and thermistor as explained with reference to Fig. 1. Since it can be formed much smaller and have a significantly smaller heat capacity than conventional elements formed using silicon, it is possible to improve the response and sensitivity due to the good thermal conductivity of silicon, and the two aspects of the present invention Since the elements can be placed very close together, there is no risk of measurement errors due to the influence of ambient temperature.

Further, since the characteristics of each element can be formed in a similar manner, there is no risk of measurement errors due to variations in characteristics, making it extremely suitable for measuring the true effective value of an AC signal.

[Brief explanation of the drawing]

Fig. 1 is a wiring diagram showing an example of a circuit for measuring true effective value of an AC signal, and Fig. 2 is a diagram showing an embodiment of the present invention.
Input terminal for AC signal to be measured, 2: DC power supply connection terminal, 3
: Output terminal, 4: Input resistance, 5 and 6: Voltage dividing resistance, r:
Differential amplifier, 8: output resistance, 9 and 10: heating resistance, 1
1 and 12: thermistor, 13 and 14: AC/DC conversion element, 15: substrate, 16: heating thin film resistor, 1r: terminal electrode, 18: temperature sensitive thin film element, 19: terminal electrode.

Claims (1)

[Scope of Claims] 1. A true effective value characterized in that a heating thin-film resistor and its terminal electrodes, as well as a temperature-sensitive thin-film element and its terminal electrodes are deposited on a silicon substrate having an insulating layer on its surface. AC/DC conversion element for measurement. 2. The AC/DC conversion element for true effective value measurement according to claim 1, wherein the insulating layer on the surface of the substrate is formed of silicon oxide. 3. The AC/DC conversion element for true effective value measurement according to claim 1, wherein the insulating layer on the surface of the substrate is formed of tantalum pentoxide. 4. The AC/DC conversion element for true effective value measurement according to claim 1, wherein the insulating layer on the surface of the substrate is formed of silicon nitride. 5. Any of claims 1 to 4, in which the heating thin film resistor is formed of a thin film of tantalum nitride or a nickel-chromium alloy, and the terminal electrode thereof is formed of a thin film of gold, platinum, aluminum, nickel, etc. An AC/DC conversion element for measuring true effective value as described in . 6. AC/DC conversion for true effective value measurement according to any one of claims 1 to 4, wherein the temperature-sensitive thin film element and its terminal electrodes are formed of a thin film of gold, platinum, aluminum, nickel, etc. element. 7 The temperature-sensitive thin film element is formed of a thin film of copper or nickel, etc., and the terminal electrode thereof is formed of a thin film of gold, platinum, aluminum, nickel, etc. according to any one of claims 1 to 4. AC/DC conversion element for true RMS value measurement. 8. The true effective value according to any one of claims 1 to 4, in which the temperature-sensitive thin film element is formed of a thin film thermistor, and the terminal electrode thereof is formed of a thin film of gold, platinum, aluminum, nickel, etc. AC/DC conversion element for measurement.