SU1196773A1 - Semi-bridge resistance meter (its versions) - Google Patents

Abstract

The invention relates to a measurement technique and can be used to measure resistances and their increments, in particular, in strain gauges. The purpose of the invention. is the measurement accuracy by increasing the measurement linearity, as well as ensuring the independence of the measurement results from the nominal resistance of the half-bridge resistors and measurements of the non-uniform resistance of the half-bridge resistors. The goal is achieved by the implementation of a power source in the form of a current source and the introduction of an inverting scale amplifier. In this case, the proposed half-bridge resistance meters will have linear characteristics; independent of the nominal resistances of the resistors to be measured. The device measures non-uniform pe-i resistors of the half-bridge, which together increases the measurement accuracy. Having only one current source in the meter, and not two voltage sources (as in the prototype) simplifies the device. 2 sec. f-ly, 2 ill. about: 1 co

Description

i

The invention relates to electrical measuring equipment and can be used to measure the resistances and their increments, in particular, in strain gauges.

The purpose of the invention is to increase the measurement accuracy by increasing the linearity of the measurement, ensuring the independence of the cut of one measurement from the nominal resistance of the half-bridge resistors, ensuring the possibility of measuring the ner-to-nominal resistances of the half bridge.

FIG. 1 and 2 show variants of the half-bridge resistance meter.

The proposed meter (Fig. 1) contains the first 1 and second 2 supply terminals of half-bridge 3, the first output terminal 4 and the second output terminal 5 connected to the common bus, operational amplifier 6, the output and inverting input of which are connected to the first terminal 1 of half-power 3 The non-inverting input of the operational amplifier 6 is connected to the output of the inverting scale amplifier 7, the input of which is connected to the second half-power supply terminal 2 3. And the second output of the current source 8, the first output of which is connected to a common bus. Between the first 1 and second 2 power terminals of the half bridge 3, the first

9 and the second 10 resistors connected in series, Obna the leads of the first and second resistors 9 and 10 are connected to the first output terminal 4.

The transfer coefficient of the inverting scale amplifier 7 is equal to the ratio of the nominal resistance of the first resistor 9 to the nominal resistance of the second resistor 10,

The second variant of the half-bridge resistance meter (Fig 2) differs from the first variant in that the inverting input of the operational amplifier 6 is connected to the second half-power terminal 2 of the half-bridge 3, and the input of the inverting scale amplifier 7 is connected to the first half-power terminal 1 of the half-bridge 3,

Half-bridge resistance meter works as follows.

Denote the nominal resistance of the first resistor 9 R, the nominal resistance of the second resistor

10R2, the transfer ratio of the inverting scale amplifier 7 is equal to

196773

P--,

2

Denote the voltages at the first and second terminals 1 and 2 of the power supply U and Uj, respectively.

The voltage Uj is fed to the input of an inverting scale amplifier 7, having a high input resistance, and is transmitted to a non-inverting input of an operational amplifier 5 operating in voltage repeater mode,

A four-wire circuit for connecting half-bridge 3 to a current source 8 that inverts the large-scale amplifier 7 and the operational amplifier 6 ensures that the measurement result is independent of the resistance of the connecting wires and therefore. (.) The system of equations describing the state of the half-bridge resistance meter in the first embodiment has the form

U.-U.

Uet, x. (2) From

(3)

jp.

g

-iy- (R, -nR,)

(four)

From the expression CA), it can be seen that the output voltage of the meter is proportional to the difference in resistance RI and RJI, the coefficient of sensesI.

the measurer is

n +

does not depend on the resistances R and Rj of resistors 9 and 10 and, therefore, the characteristic of the meter is linear in any range of variation of these resistances,

In the particular case of and,

Uebu-r (R -, - Rz

(five)

When the resistance R and Rj change, the output voltage of the meter gets a proportional increment) - (-2-GlRi-4R2). If one of the resistors, such as resistor 10, is exemplary and does not change its resistance, the bw voltage of the meter is proportional to the change in resistance of the other resistor. From the expression (41 it follows b1, i.e. in this case, the characteristic of the meter is linear and does not depend on the nominal resistances of the resistors 9 and 10. In the second variant, the meter has a transmission efficiency of the inverting scale amplifier 7 and is IR IR, and the meter operation is similar to the meter in the first embodiment. Due to the implementation of the power source as a current source and the introduction of an inverting scale amplifier, the proposed half-bridge resistance meters have linear characteristics independent of the nominal resistances from measurable resistors, provide the ability to measure non-uniform resistors in the half-bridge, which together increases the measurement accuracy .. In addition to TorOj, the presence of only one current source in the meter, and not other voltage sources as in the well-known device, simplifies the design, Ф о p of invention 1, a half-bridge resistance meter containing a power source, the first output of which is connected to a common bus, a half-bridge, of the first and second 734 resistors sequentially connected, the first output a lemma connected to the common pins of half-bridge resistors, a second output terminal connected to a common bus, a single-amplifier, the output and inverting input of which is connected to the second pin of the first half-bridge resistor, characterized in that, in order to increase the measurement accuracy, An inverting scale amplifier is introduced into it, and the power source is designed as a current source, the second output of which is connected to the second output of the second half-bridge resistor and the input of the inverting scale amplifier, the output of which is connected with the non-inverting input of the operational amplifier, and the transfer ratio of the inverting scale amplifier is the ratio of the nominal resistance of the first half-bridge resistor to the nominal resistance of the second half-bridge resistor, 2, a half-bridge resistance meter containing a power source, the first output of which is connected, with a common busline half-bridge connected in series the first and second resistors, the first output terminal connected to the common terminals of the half-bridge resistors, the second output terminal, with integrated with a common bus, an operational amplifier, the output of which is connected to the second output of the first half-bridge resistor, characterized in that, in order to improve the measurement accuracy, an inverting scale amplifier is inserted into it, and the power source is implemented as a current source, the second output of which is connected to the second terminal of the second half-bridge resistor and the inverting input of the operational amplifier, non-inverted-. Its input is connected to the output of an inverting scale amplifier, whose input is connected to the second output of the first half-bridge, and the transfer coefficient of the inverting large-scale amplifier is equal to the ratio of the nominal resistance of the second half-bridge resistor to the nominal resistance of the first half-bridge resistor.

Claims (1)

Claim I. The half-bridge resistance meter, comprising a power source, a first output connected to the common bus, half-bridge, series connected first and second resistors of a first output terminal coupled to common terminals rezne- _(tori half bridge, a second output terminal connected to common. bus, one5 is a portable amplifier, the output and inverting input of which is connected to the second output of the first half-bridge resistor, characterized in that, in order to increase the exact measurement of 10 measurements, an inverting scale amplifier is introduced into it a power supply, and the power source is made in the form of a current source, the second output of which is connected to the second output of the second half-bridge resistor15 and the input of an inverting scale amplifier, the output of which is connected to the non-inverting input of the operational amplifier, and the transfer coefficient of the inverting scale amplifier is equal to the ratio of the nominal resistance of the first resistor half-bridge to the nominal resistance of the second half-bridge resistor, 25 2. A half-bridge resistance meter containing a power source, the first output of which is connected to a common bus _l half-bridge from the first and second 30 resistors connected in series, the first output terminal connected to the common terminals of the half-bridge resistors, the second output terminal connected to the common bus, an operational amplifier whose output is connected to the second terminal of resistor lane ³⁵ Vågå half-bridge, characterized in that, in order to improve measuring accuracy, it is entered masshtab40 ny inverting amplifier, and a source of pi The power supply is designed as a current source, the second output of which is connected to the second output of the second half-bridge resistor and the inverting input of the operational amplifier, the non-inverting input of which is connected to the output of the inverting scale amplifier, the input of which is connected to the second output of the first half-bridge resistor, and the transfer coefficient of the inverting scale amplifier is the ratio of the nominal resistance of the second half-bridge resistor to the nominal resistance of the first half-bridge resistor.