JPH0248865B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention adds an adjustment circuit for zero point adjustment or zero point movement temperature compensation in a bridge circuit, particularly a full bridge circuit in which resistance elements whose resistance value changes according to changes in physical quantities are arranged on four sides. This paper relates to improvements to bridge circuits.

Generally, full-bridge circuits, in which resistance elements such as semiconductor strain gauges are arranged on four sides and whose resistance value changes according to changes in pressure, length, and other physical quantities, are widely used as electrical measurement means, and various types of It has the advantage that a simple and accurate electrical measurement signal can be detected even under measurement conditions. In this type of bridge circuit, zero point adjustment of the bridge output and zero point shift temperature compensation are required to improve bridge detection accuracy. In other words, zero point adjustment is the adjustment of the bridge output (offset voltage) caused by the unbalance of the resistance values on the four sides to zero in order to obtain measurement conditions that make the bridge output zero without any physical quantities being added. In addition, zero point shift temperature compensation is the shift of the zero point output of a bridge circuit due to temperature, which is caused by thermal stress due to the influence of temperature changes or variations in the resistance temperature characteristics of the element itself, regardless of physical quantities (zero point shift temperature compensation). ). Each of the above-mentioned compensation operations is essential in a bridge circuit, especially when using elements with large resistance temperature coefficients such as semiconductor strain gauges as each resistance element, or when detecting changes in physical quantities with extremely high precision and stability. It is necessary to perform accurate zero-point shift temperature compensation.

FIG. 1 shows a conventional bridge circuit to which a zero point adjustment and zero point movement temperature compensation circuit is added, and the four sides of the bridge circuit 10 have resistive elements 12, 14,
6 and 18, respectively, and in order to perform the compensation, a series resistor rs is connected to the resistive element 12, and a parallel resistor r _P is connected to the resistive element 18, and both resistors r _S and r _P
By adjusting the resistance values of the four sides, the resistance values and resistance temperature coefficients of the four sides are simultaneously balanced, and zero point adjustment and zero point shift temperature compensation are performed. Both resistances
_rS and _rP are resistive elements that do not substantially change their resistance with respect to temperature changes, that is, have a small temperature coefficient of resistance.

In FIG. 1, the zero point adjustment is performed by the bridge circuit 10.
This is done by adjusting the resistance values of each insertion resistor r _S and r _P so that the resistance values of the four sides of the two pairs of resistance values of two opposing sides are equal, but of course, only this zero point adjustment It is clear that if this is done, the temperature coefficient of resistance of the adjusted side will change. On the other hand, in zero-point movement temperature compensation, the resistance temperature coefficient of the four sides is balanced by using an adjustment resistor inserted in the side with the large resistance temperature coefficient, and the resistance temperature coefficient of the four sides can be balanced, but of course, even in this case, the adjustment The resistance value of the side changes,
It is clear that the zero point moves. That is,
Since zero point adjustment and resistance movement temperature compensation have a mutual correlation, during actual adjustment, the resistance values of the series resistance r _S and parallel resistance r _P and the side connecting them should be selected appropriately. As a result, zero point adjustment and zero point movement temperature compensation are performed at the same time, and the selection of each resistance value at this time is set using the following approximate formula, as is well known.

r _S = 2R△V _T /V _io・R/△R−△V _O /V _io …(1) formula r _P = R/2 (△V _O /Vin+△V _T /Vin・R/△R) …(2
) formula In the above formula, R is each resistance element 12, 14, 1
6 and 18 are the same resistance values of each element when diffused semiconductor strain gauges are used, and △R is the resistance value of each resistance element 1.
2, 14, 16, and 18 with respect to temperature change △T, V _io is the voltage between the input terminals of bridge circuit 10, △V _O is the zero point output voltage, △V _T is the temperature change △
This is the zero point movement amount with respect to T.

Note that the above equation is an approximate solution, so the actual adjustment is
After one of the resistors r _S and r _P is connected to a predetermined side, the other resistor is adjusted so that the zero point output of the bridge circuit 10 actually becomes zero.

In the conventional bridge circuit, the resistor element 1
2, 14, 16, and 18 are formed by semiconductor strain gauges and the resistance value is 1 to 2 kilohms, the series resistance r _S is about 100 ohms or less, and the parallel resistance r _P
is generally several tens of kilohms or more, and in such an actual bridge circuit, there is a drawback that it is extremely difficult to finely adjust the values of each adjustment resistor r _S and r _P . In other words, when trying to finely adjust the zero point output to, for example, about ±0.1 mV or less, the fine adjustment of the series resistor r _S requires 0.1 mV or less.
It becomes necessary to finely adjust the value to below ohm.
For this reason, a problem arises in that the series resistor r _S must be constructed from a combination of a plurality of fixed resistors having adjustable small resistance values, or a variable resistor of about 1 ohm must be used. however,
The combination of a plurality of fixed resistors has the disadvantage of making the bridge circuit complicated and expensive, and the variable resistor with a low resistance value has the disadvantage of increasing its size. When the above-mentioned fine adjustment is performed using a parallel resistor r _P , there is a problem that the shape of the parallel resistor r _P becomes large and that an appropriate resistance element cannot be obtained. However, the problem arises that the insertion edge must be changed, and in both cases, fine adjustment is extremely difficult.

In particular, the fine adjustment may cause a big problem when the bridge circuit 10 is used as a pressure transducer. In other words, when configuring an absolute pressure transducer with a bridge circuit and detecting atmospheric pressure fluctuations or pressure fluctuations above atmospheric pressure as absolute pressure changes, including atmospheric pressure fluctuations, the bridge output is set to zero at standard atmospheric pressure. However, at this time, the above-mentioned difficulty in adjustment is likely to occur. Generally, the pressure acting on the pressure transducer is zero (vacuum) and
Even if the output voltage becomes almost zero with no strain occurring in the strain-generating part, and the output change due to temperature at that time is small, the zero point output at standard atmospheric pressure is itself zero point. It has a moving temperature characteristic, which is shown in FIG. In other words, when the voltage △V _O corresponding to the standard atmospheric pressure output is set as the zero point output, the zero point shift △V _T corresponds to the output decrease of the standard atmospheric pressure output △V _O shown in Figure 2 as the zero point movement temperature characteristic. occurs. Therefore, the zero point output △V _O and zero point movement △V _T in Figure 2
If the values of the series resistance r _S and parallel resistance r _P are determined so that both are zero, then the parallel resistance r _P is generally
It is more than 100 kilohms, and the connection side is also the first
There is a problem that the device is separated into either the element 16 or 18 shown in the figure, and its setting becomes extremely difficult. This is done by increasing the resistance value on the side of the element 12 using the series resistor r _S to shift the zero point output to the negative side, and at the same time decreasing the resistance temperature coefficient on this side to change the zero point shift temperature characteristic to the positive side. This is because the effect of reducing the zero point output to zero and the effect of zero point movement temperature compensation can be obtained only with the resistor r _S , and the parallel resistor r _P is used only for slightly adjusting the zero point output.

In either case, the conventional device has the disadvantage that it is extremely difficult to obtain accurate fine adjustment because the resistance values of the series-parallel resistors are in a range that is difficult to adjust.

The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to provide an improved bridge circuit that allows fine adjustment of the zero point to be performed extremely easily.

In order to achieve the above object, the present invention connects a resistive element whose resistance value changes according to a change in physical quantity to each of the four sides, connects a power source between a pair of opposing power terminals, and connects a power source between a pair of opposing power terminals. In a bridge circuit that extracts an output voltage from an output terminal, a bias parallel resistor having a sufficiently larger resistance value than the resistance element on that side is connected in advance to any one side of the bridge circuit, and the bias parallel resistor is connected in advance. A parallel resistor for adjustment is connected to the bridge side adjacent to the bridge side, and a series resistor for adjustment is connected to the other bridge side, and the bias parallel resistor, parallel adjustment resistor, and series resistor are connected to temperature changes. By forming a resistance element that does not substantially change the resistance and connecting a bias parallel resistance in advance, the value of the adjustment parallel resistance to be connected subsequently can be set to the same level as the bias parallel resistance. It is characterized in that the resistance value is set within a range, and the zero point adjustment and zero point movement temperature compensation of the bridge circuit are performed using a series resistor and a parallel resistor for adjustment.

Preferred embodiments of the present invention will be described below based on the drawings.

FIG. 3 shows the first bridge circuit according to the present invention.
An embodiment is shown, and the same members as those in the conventional circuit shown in FIG. Each resistance element 12, 14, 16, 18 in FIG.
A preferred embodiment of a pressure transducer including a bridge circuit 10 is shown in FIG.

In FIGS. 4 and 5, a silicon diaphragm 20 made of a thin plate of silicon single crystal is glass-bonded to a base 22 at its periphery in a vacuum, and a thin strain-generating portion 24 is formed in its center. , resistance elements 12 and 16 made of diffused type semiconductor strain gauges are disposed at the center of the surface of the strain-generating portion 24, and resistance elements 1 also made of diffused type semiconductor strain gauges are disposed at the periphery.
4 and 18 are each formed by a diffusion method. Each of the elements 12, 14, 16, and 18 is connected in series by a diffusion lead portion or vapor-deposited aluminum wiring formed on the silicon diaphragm 20, and both ends and three connection points are connected to the periphery of the silicon diaphragm 20. The bridge circuit 10 shown in FIG. 3 is connected to the provided aluminum electrode lead terminals 26 to 34 to form the bridge circuit 10 shown in FIG. Therefore, when pressure is applied to the silicon diaphragm 20, the resistance element 1
2 and 16 and the resistance elements 14 and 18 are subjected to strains in opposite directions on the tension side and compression side, and the resistance values change in opposite directions, making it possible to accurately detect pressure electrically. As is clear from FIG. 5, a vacuum reference pressure chamber 36 is formed between the strain generating part 24 and the base 22, and constitutes an absolute pressure type pressure transducer. By communicating the reference pressure chamber 36 with the outside through the back pressure hole 38 provided in the base 22, a gauge pressure type or differential pressure type pressure transducer can be constructed.

As described above, the bridge circuit 10 according to the present invention can be used as the pressure transducer shown in FIGS. 4 and 5, etc. Next, the structure of the regulating circuit according to the present invention shown in FIG. 3 will be explained.

In FIG. 3, opposing power supply terminals 40 and 42 of the bridge circuit 10 are connected to the positive and negative poles of a power supply 44, respectively, and a DC voltage is supplied to the bridge circuit 10. The other pair of opposing output terminals 46 and 48 of the bridge circuit 10 are connected to a positive output terminal 50 and a negative output terminal 52, respectively.

Then, on each of the four sides of the bridge circuit 10, for example, the resistance element 12 is
A series resistor 54 for adjustment is connected to the side.
Furthermore, for example, in the embodiment, a bias parallel resistor 56 is connected to the side to which the resistance element 16 is connected, and in the embodiment, the resistance element 1 is connected to the side adjacent to this side.
A parallel adjustment resistor 58 is connected to the side to which 8 is connected. The series resistor 54 and both parallel resistors 56 and 58 have temperature coefficients of resistance that are sufficiently small compared to the temperature coefficients of resistance of the resistance elements 12, 14, 16, and 18 made of diffused semiconductor strain gauges, and are substantially free from temperature changes. It is formed from a resistance element that does not cause a change in resistance due to the change in resistance.

The first embodiment of the present invention has the above configuration, and its adjustment operation will be explained according to the following adjustment procedure.

(1) The resistance value of the bias parallel resistor 56 is preferably larger than that of the diffused semiconductor strain gauge.
The bridge circuit 10 is constructed by selecting an arbitrary resistance value from a range that is 10 times or more larger, and which is easy to select and adjust, and which is actually the easiest to use.
In the embodiment of any one side, it is connected to the connecting side of the resistive element 16. When the resistance value of the semiconductor strain gauge is approximately 1 to 2 kilohms, the resistance value of the parallel resistor 56 is preferably selected from a range of several tens of kilohms to 100 kilohms.

(2) Series resistor 54 and adjustment parallel resistor 5 in Figure 3
8 is not connected, that is, the series resistance 5
4 is short-circuited and the pressure transducer is set to the zero point state (the state in which the bridge output is desired to be zero), and the value of the zero point output and the zero point shift temperature characteristic are determined.

(3) The resistance values of the series resistor 54 and adjustment parallel resistor 58 necessary to set the value of the zero point output obtained in the previous two sections to zero and to compensate for the temperature of the zero point shift temperature characteristic and the connection sides of these resistors are as described above ( Calculated using equations 1) and (2).

(4) Connect the series resistor 54 and the adjusting parallel resistor 58 corresponding to the calculation results obtained from the previous three items to the predetermined sides, and then connect the adjusting parallel resistor 58 so that the zero point output of the bridge circuit 10 actually becomes zero. Adjust the resistance value of the resistor 58. (In addition, the resistance value of the parallel adjustment resistor 58 can also be adjusted directly after connection, and in this case, the calculation of equation (2) above is unnecessary.) (5) Zero point shift temperature compensation can be further enhanced. In order to do it accurately,
After the adjustment in the previous four terms, the value of the zero point output and the zero point movement temperature characteristic are determined again, and based on these, the calculations and adjustments in the third and fourth terms are performed. At this time, in term 3, the series resistance 5
The correction value of 4 is obtained, and in the 4th term, the value of the series resistor 54 is corrected according to the correction value, and then the resistance value of the parallel adjustment resistor 58 is adjusted to finely adjust the zero point output. By repeating this fine adjustment a necessary number of times, the zero point fine adjustment of the present invention can be performed.

As explained above, according to the first embodiment circuit, the parallel bias resistor 56, whose resistance value is easily selected and arbitrarily selected from the range that is most easily used in practice, is installed in advance on any side of the bridge circuit 10. That is, after connecting to the connection side of the resistance element 16 in the embodiment, the values of the series resistor 54 and the adjusting parallel resistor 58 for zero point adjustment and zero point movement temperature compensation are determined, so naturally, the values of the adjusting parallel resistor 58 are determined. The resistance value is a bias parallel resistor 5 whose resistance value is determined in advance.
The resistance value is close to the resistance value of No. 6, and the connection side is also necessarily set to the adjacent side sandwiching the power supply terminals 40 and 42. That is, bridge circuit 1
If parallel resistors of the same resistance value are connected to two adjacent sides of 0, the resistance value of both bridge sides will change in the same way, and the resistance temperature coefficient of both bridge sides will also show a similar change. Therefore, such connection of both column resistors to adjacent sides has no effect on the zero point output and zero point movement temperature characteristics of the bridge circuit 10, and the resistance value of the parallel resistor 58 used for adjustment can be easily adjusted. In order to obtain a suitable resistance value range and to ensure zero point adjustment and zero point movement temperature compensation, it is sufficient to provide a parallel resistor 56 used as a bias for setting the resistance value of the parallel resistor 58 in advance on any bridge side. That is understood.

As described above, according to the present invention, by connecting the bias parallel resistor to any side of the bridge circuit in advance, the resistance value of the adjusting parallel resistor can be arbitrarily selected from a desired resistance value range. It becomes possible.

As a specific example, when trying to make the output of the above-mentioned absolute pressure transducer zero at standard atmospheric pressure, the input DC voltage V _io of the bridge circuit 10 = 6V, the resistance of each resistance element 12, 14, 16, 18. Value R = 1800 ohm, its resistance temperature coefficient is 0.14% per 1℃, the output voltage at zero pressure (vacuum) is ±30mV, the output sensitivity at standard atmospheric pressure is 60mV, and the output sensitivity temperature coefficient is -0.14% per 1℃. (From this, △V _T per 1℃
becomes −0.084mV. ), a series resistor 54, a bias parallel resistor 56, and an adjustment parallel resistor 58.
Assuming that the resistance values of are r54, r56, and r58, respectively,
In the conventional device shown in Figure 1, r54 = approximately 50 to 90 ohms (connected in series with resistive element 12) and r58 = approximately
200 kilohms to ∞ (connected in parallel to resistive element 16 or 18), whereas in this embodiment shown in Fig. 3, if the bias parallel resistance value r56 is set to 100 kilohms, the series resistance value r54 becomes the same as before. about 50 similar
~90 ohms (connected in series with resistor element 12), but the parallel resistance r58 for adjustment is approximately 50 to 100 kilo ohms (connected in parallel to resistor element 18), and from this, the parallel resistance value r58 for adjustment is biased. The parallel resistance r56 can be set to a value close to that of the parallel resistance r56, making adjustment extremely easy, and the bridge side to which it is connected is also determined to be the connecting side of the resistor element 18 in a particular bridge side embodiment.

As described above, after determining the low resistance values of the series resistor 54 and the parallel resistor 58 and connecting them to each specific bridge side, the parallel resistor 58 is connected so that the zero point output of the circuit of this embodiment actually becomes zero. The resistance value of is adjusted. Since the resistance value of this parallel resistor 58 can be set to a range that is actually most convenient for use with the bias parallel resistor 56, zero point adjustment can be performed much more easily than in the past. Furthermore, according to the present invention, since the connection bridge side of the parallel adjustment resistor 58 is specified, there is no need to change the connection side each time the adjustment is made as in the conventional case, and the configuration of the adjustment circuit can be significantly simplified. becomes. Further, fine adjustment of the zero point output can also be performed by making a rough adjustment in advance by adjusting the parallel resistor 58, and then adjusting the resistance value of the parallel resistor 56 for bias within a minute range, and this fine adjustment does not have a large effect on the zero point movement temperature characteristics, so even when trying to finely adjust the zero point output to 0.1 mV or less, both parallel resistors 5
This has the advantage that accurate zero point adjustment can be performed by adjusting the points 6 and 58.

Note that the power terminal 40 in the embodiment of FIG.
42 and the output terminals 46, 48, the same effect can be obtained even if the terminals 40, 42 are used as output terminals and the terminals 46, 48 are used as power supply terminals.

Furthermore, in the embodiment, the power supply 44 is normally a constant voltage power supply, but the resistance elements 12, 14,
It is also possible to use the power source 44 as a constant current power source in order to compensate for the temperature sensitivity characteristics when the sensors 16 and 18 are formed of diffused semiconductor strain gauges.

A second embodiment of the present invention is shown in FIG.
The same members as in the first embodiment shown in the drawings are given the same reference numerals and their explanations will be omitted. The second embodiment is characterized in that a zero point fine adjustment circuit is added to enable even finer zero point adjustment. The circuits are connected, the parallel circuit forming a zero point fine adjustment circuit, and the intermediate terminal of the variable resistor 62 is connected to the positive output terminal 50.

The parallel combined resistance value of the fixed resistor 60 and the variable resistor 62 is set so that the product of the current flowing through the parallel resistor and the parallel resistance value becomes a predetermined adjustment voltage width, and among both resistors, the fixed resistor The variable resistor 60 is set to a value close to the parallel combined resistance value, while the variable resistor 62 is set to a resistance value as large as possible, easy to select, and easy to use in practice. The zero point fine adjustment circuit in FIG. 6 is connected to the bridge circuit 10 from the time of initial assembly, and the intermediate terminal of the variable resistor 62 is set at approximately the center position of the resistance value.
The same zero point adjustment and zero point movement temperature compensation as in the embodiment may be performed, or the bridge circuit 10 may be additionally connected to the bridge circuit 10 after the zero point adjustment and zero point movement temperature compensation are performed. Note that the power source 44 in FIG. 6 is formed from a constant current power source.

The second embodiment of the present invention has the above configuration, and its operation will be explained below.

The current of the resistance elements 12 and 18 flows through the zero point fine adjustment circuit consisting of the fixed resistor 60 and the variable resistor 62, and a voltage drop is generated across the fixed resistor 60 equal to the product of the parallel combined resistance value and the current resistance value. . At this time, the intermediate potential of the variable resistor 62 becomes equal to the potential of the output terminal 46 in the first embodiment of FIG. 3 to which the zero point fine adjustment circuit is not additionally connected. Therefore, when the intermediate terminal of the variable resistor 62 is at the center position of the resistance value, the output voltage obtained between both output terminals 50 and 52 is the same value as the output voltage when the zero point fine adjustment circuit is not additionally connected. It is understood that
Then, by moving the intermediate terminal of the variable resistor 62, an output voltage deviated by a constant voltage corresponding to the intermediate terminal movement position of the variable resistor 62 is obtained from the positive output terminal 50. This makes it possible to adjust the zero point output of the circuit 10. The adjustment voltage width at this time is equal to the product of the parallel composite value and its current value, and it is clear that in order to make fine adjustments by reducing the voltage adjustment width, the parallel composite value should be made smaller. It is. This parallel combined resistance value can be reduced by simply reducing the resistance value of the fixed resistor 60, and the resistance value of the variable resistor 62 can be arbitrarily set to a variable resistance value that is easily available and convenient for actual use. It becomes possible to obtain a bridge circuit that can be easily fine-tuned at a low cost.

As a specific example, a current of 3 mA is supplied from the power supply 44, and approximately half of the current is supplied to the resistive elements 12 and 18.
Assume that a current of about 1.5mA flows, and at this time ±
In order to configure a circuit that can perform fine adjustment of about 1 mV (2 mV in adjustment voltage width), the parallel combined resistance value should be about 1.3 ohm. If the resistance value of the fixed resistor 60 at this time is approximately 1.3 ohm, then
As the variable resistor 62, an element having a resistance value of 10 to 100 ohms or more may be used, and it is possible to use a small and standard type element as the variable resistor.

Further, according to the embodiment shown in FIG. 6, the adjustment range by the variable resistor 62 extends from the positive side to the negative side.
Even when an IC DC amplifier or the like is directly connected to the bridge circuit 10 in order to amplify the output of the bridge circuit 10, the zero point output of the bridge circuit 10 is set to the input offset voltage of the IC DC amplifier (the input that makes the output of the IC DC amplifier zero). It can be adjusted in both positive and negative directions so that it is equal to the voltage (voltage), making it possible to easily adjust the zero point of the output of the IC DC amplifier.

A third embodiment of the present invention is shown in FIG.
This embodiment is characterized in that a span adjustment resistor is additionally connected to the second embodiment shown in the figure, and the same members as those in FIG.

In the third embodiment, the fixed resistors of the zero point fine adjustment circuit are fixed resistors 60a and 60b having almost equal resistance values.
A span adjustment resistor 6 is connected between the common connection point of both fixed resistors 60a and 60b and the negative output terminal 52.
4 is additionally connected.

In other words, if the resistance value of the span adjustment resistor 64 is made small, the output voltage can be adjusted by utilizing the fact that the output voltage between the output terminals 46 and 48 decreases with respect to the voltage change obtained between the output terminals 46 and 48. Consists of resistance for span adjustment. Therefore, by arbitrarily changing the resistance value of the span adjustment resistor 64, it is possible to span-adjust the detected voltage to an arbitrary level. In the embodiment shown in FIG. 7, one end of the span adjustment resistor 64 is connected to the connection point of the fixed resistors 60a and 60b having the same resistance value, so during zero point adjustment, the span adjustment resistor 64
Therefore, during zero point adjustment, the span adjustment resistor 64 does not have any adverse effect on the zero point adjustment action.

As explained above, according to the present invention, in a bridge circuit that performs zero point adjustment and zero point movement temperature compensation by connecting a series resistor and a parallel resistor for adjustment to a resistance element of a full bridge circuit, the bias parallel resistor is connected in advance to the bridge circuit. The resistance value of the parallel resistor for adjustment connected to any one side of the side and connected to this side and the adjacent bridge side can be set in advance to a resistance value within a desired range. It becomes possible to easily select a value, and it becomes possible to obtain a bridge circuit that is small and easy to finely adjust.

Furthermore, in the present invention, zero point adjustment can be made with high precision by connecting a zero point fine adjustment circuit consisting of a parallel connection of a fixed resistor with a small resistance value and a variable resistor with a standard resistance value that is easily available. Moreover, it has the advantage that it can be obtained with a simple circuit configuration.

As described above, according to the present invention, a small and highly accurate bridge circuit can be provided at low cost.
It becomes possible to obtain a bridge circuit that can be applied to a wide range of measuring instruments.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing a conventional bridge circuit with an adjustment resistor added, Fig. 2 is a temperature characteristic diagram when the conventional bridge circuit is used as a pressure transducer, and Fig. 3 is a bridge circuit according to the present invention. preferred first
A circuit diagram showing an embodiment, FIG. 4 is a perspective view showing an embodiment in which the bridge circuit of FIG. 3 is configured as a pressure transducer, FIG. 5 is a sectional view of the main part of FIG. 4, and FIG. FIG. 7 is a circuit diagram showing a second preferred embodiment of the bridge circuit according to the present invention, and FIG. 7 is a circuit diagram showing a third preferred embodiment of the bridge circuit according to the present invention. 10... Bridge circuit, 12, 14, 16, 18
...Resistance element, 40, 42...Power supply terminal, 44...Power supply, 46, 48...Output terminal, 54...Series resistance, 5
6...Parallel resistance for bias, 58...Parallel resistance for adjustment, 60...Fixed resistance, 62...Variable resistance, 64...Span adjustment resistance.

Claims (1)

[Claims] 1. A resistance element whose resistance value changes according to a change in physical quantity is connected to each of the four sides, and a power supply is connected between a pair of opposing power supply terminals, and an output voltage is output from the other pair of output terminals. In the bridge circuit from which the output is taken out, a bias parallel resistor having a sufficiently larger resistance value than the resistance element on that side is connected in advance to any one side of the bridge circuit, and the bridge side adjacent to the bridge side to which this parallel bias resistor is connected is connected in advance. A parallel resistor for adjustment is connected to the side of the bridge that is to be adjusted, and a series resistor for adjustment is connected to the other bridge side, so that the bias parallel resistance, parallel adjustment resistance, and series resistance are substantially controlled against temperature changes. It is formed from a resistance element that does not cause a resistance change, and by connecting a bias parallel resistance in advance, the value of the adjustment parallel resistance connected afterwards is set to the same resistance value range as the bias parallel resistance. A bridge circuit characterized in that the zero point adjustment and zero point movement temperature compensation of the bridge circuit are performed using a series resistor and a parallel resistor for adjustment. 2. In the device according to claim 1, a zero point fine adjustment circuit consisting of a parallel circuit of a fixed resistor and a variable resistor is connected to one output terminal of the bridge circuit,
A bridge circuit characterized in that a bridge output is taken out from an intermediate terminal of the variable resistor, and the zero point output is finely adjusted by adjusting the variable resistor. 3. A bridge circuit according to claim 1 or 2, characterized in that a span adjustment resistor is connected between the output terminals of the bridge circuit.