SU1524004A1 - Method of converting nonelectric quantity to electric signal and converter of nonelectric quantity to electric signal - Google Patents

Abstract

The invention relates to a measurement technique and can be used to create new samples of strain gauge equipment at a carrier frequency. The purpose of the invention is to improve the accuracy of conversion by increasing the stability and stability of the power supply circuits of the strain gauge bridge by feedback voltage. This is achieved in that the supply voltage of the measuring bridge is formed by summing the voltage of the master oscillator, the modulated carrier frequency and the amplified difference between the average values of the rectified voltage on the master oscillator and the active component of the voltage on the measuring bridge. At the same time, the stability of the power supply circuits of the measuring bridge is determined by the realized gain, and the stability, by the demodulation process, by modulation in the form of feedback on the average value of the active component of the supply voltage. In order to implement the method, two identical compensating units are included in the power supply circuit of the measuring bridge. 1 hp f-ly, 3 ill.

Description

The invention relates 1: to the measurement technique and can be used to create nopmh samples of strain gauge equipment at the carrier frequency.

The aim of the invention is to improve the accuracy of the conversion by increasing the stability and stability of the power supply circuits of the strain gauge bridge with a feedback voltage.

Figure 1 shows a diagram of an apparatus for carrying out the method; Fig. 2 is a diagram of a variant of the device when the measuring bridge is switched on with a transformer isolator; on

fig.Z - the equivalent circuit of the device depicted in figure 1.

A device for carrying out the method (FIG. 1) comprises a measuring bridge 1, a measuring amplifier 2, a master oscillator 3, a generator 4 control signals, amplifiers 5, voltage followers 6 and two equal compensating units 7, each of which contains a key element 8, one input through a resistor 9 is connected to the output of a corresponding follower 6 of voltage j second through a resistor 10 to the output of a master oscillator 3 controlling

the input is from the output of the control signal generator 4, and the output is connected to the integrator input performed on the operational amplifier 11 with a coupling capacitor 12, the output of the operational amplifier 11 and the output of the driving generator 3 are connected to two inputs of the signal multiplier 13, the output which is connected to one of the inputs of the adder 14, the second input of which is connected to the output of the master oscillator 3, and the output - to the input of the amplifier 5.

A device with transformer isolation sensors (Fig 2) contains a measuring bridge 1, a measuring amplifier 2, a master oscillator 3, a generator 4 control signals, an amplifier 5, a repeater 6 and a compensating unit 7 containing a key element 8, one input of which through a resistor 9 is connected to the output of the voltage follower 6, the second through a resistor 10 to the output of the master oscillator 3, the control input to the output of the generator 4 of the control signals, and the output connected to the integrator's input made on the operational amplifier 11 s condensate rum 12 feedback, while the output of the operational amplifier 11 and the output of the master oscillator 3 is connected to two inputs of the signal multiplier 13, the output of which is connected to one of the inputs of the adder 14, the second input of which is connected to the output of the master oscillator 3, -a output amplifier input 5.

The device (Fig, 1) works as follows.

The power supply voltage of the carrier frequency from the master oscillator 3 is fed to the input of two identical compensating blocks 7. In each such block on the adder 14, it is added to the feedback voltage from the output of the signal multiplier 13 and through the corresponding power amplifier 5 as a voltage The power is supplied to the measuring bridge 1. The feedback voltage is formed from the voltage on the supply diagonal of the measuring bridge 1 by modulating the difference frequency of the rectified signals on the multiplier 13 aprons on master oscillator 3 and active voltage component on meter 0

five

0

five

Mr. Bridge 1. Subtraction and rectification operations; These voltages are made on resistors 9 and 10, key voltage, step 8, and integrator. In this case, the key element 8 and the resistors 9 and 10 form a single-half-time synchronous detector, which in the first work cycle period emits a negative half-wave of the active component voltage on the measuring diagonal of bridge 1, and in the second half-period - a positive half-wave voltage of the master oscillator 3 The time-averaged capacitor 2, the total current flowing through the key element 8, is converted into an increased voltage difference at the output of the operational amplifier 11 of the integrator and is transmitted to the input of the var Residents 13 signals to the other input thereof receiving a voltage reference generator 3. The key operation control member 8 is produced from the generator 4 is controlled Yu1tsih signal synchronously in phase voltage and the carrier frequency. The accuracy of voltage transfer from the supply diagonal of the measuring bridge 1 to the input of the resistor 9 is ensured by using a voltage follower 6 with a high input resistance. The output voltage is formed on the measuring amplifier 2 by amplifying and demodulating the voltage on the measuring diagonal of the bridge 1.

The use of the invention makes it possible to significantly increase the stability and stability of the power supply circuits of the measuring bridge with the voltage of the carrier frequency, which improves the accuracy of measuring the deformation. Due to the high stability of measuring amplifiers in modern tensometric equipment at the carrier frequency, the conversion accuracy is determined mainly by the stability and stability of the active component of the bridge supply voltage. Therefore, improving power supply circuit parameters. Directly improves conversion accuracy.

The effectiveness of the method can be estimated from the analysis of the equivalent circuit 5 (fig.Z), corresponding to the device in figure 1.

The diagram shows the adder 14 with the transfer coefficient K, 1,

0

five

0

five

0

compensating unit 7 with Transmission factor K, power amplifier 5 of measuring bridge with transmission coefficient K, 1, parameters of power cable for bridges I, and K, load R

l

m

equivalent to the resistance of the bridge from the side of the power diagonal.

The magnitudes of the supply voltages tlj are determined. (power supply voltage of the bridge) and &, „(active component R., cos 2

and

 1U

- R.

RM

and. and, - (and, „

 where and - the supply voltage is

frequencies;

(arctgtoL / CR + R). Hence, the device transmission coefficient is found.

1 + K

R -i-E- R cos it

The resulting expression allows you to determine the change in AND depending on the change in inductance and cable resistance or the resistance of the switches of the sensor switches from the measuring bridges and feedback coefficient K. For example, with R, 25 Ohms, R d 10 Ohms and cos uf 0, 5, the known method gives 1 d ,,., / Г, 0.9 at an unbalanced frequency of 20 kHz and the unstable operation of the power supply circuits of the measuring bridge, and npeAjiaraebn-ii: the method provides high stability and gives and

0.956 with

and ma / t. 77 at

k, 100

G.- 200. This shows that the implementation of the method significantly reduces the dependence of the active component of the carrier voltage on the parameters of the cables and the resistance of the measuring bridges. This means an increase in stability and accuracy of conversion. This further improves the high stability of the power supply for a wide range of cable lengths,

Claims (1)

Invention Formula 1, a method for converting a non-electric quantity into an electrical signal, comprising supplying a voltage of the carrier frequency to a power supply diagonal of a strain gauge  ) which bridge and measure the voltage unbalance on the measuring diagonal of the strain gauge bridge, characterized in that, in order to improve the accuracy of the measurement, the active component of the Carrier voltage is distinguished on the diagonal of the power of the strain gauge bridge; and the selected active component, determine the difference of the intermediate voltage of the carrier frequency and the active component, summarize the voltage J5 and the voltage proportional to the difference of the rectified voltage, and apply to iagonal power bridge strain gauge. 0 five 0 2, A converter of non-electric magnitude into an electrical signal containing a strain gauge bridge, measuring diagonal is connected to the input of the measuring amplifier, and supplying diagonal is connected to the outputs of the corresponding power amplifiers and to the inputs of the corresponding voltage repeaters, which drive the generator, the first output of which is connected to the common voltage, and a generator of control signals, which is also distinguished by the fact that, in order to improve the measurement accuracy, in which VBed 1 1Y are two compensating units, each of which contains cells chevoy element, the first input of which is connected via a resistor to a first EHODOM kompensiruyup |, its block, the second input key e; to meita through resistor soedg. - ai with the second input of the compensating unit, the control input of the key element is connected to the third input of the compensating unit, and the output of the key element is connected to the First input ;; о11 of the integrator, the second input of which is connected to the common bus consisting from the operational amplifier with a capacitive feedback, the output of the integrator is 0 dinep r the first input of the non-multiplier, the second penetration of which is connected to the second input of the compensating unit, to which the first input of the adder is also connected, the second input of which is connected to the output of the alternator and the output .jTOpa is connected to the output of the compensating unit, the first input of which is connected to the output of the corresponding voltage repeater,. five 0 five five the second input is connected with the corresponding one to one of the outputs of the master oscillator, the third generator, and the compensating output is connected to the generator output (its unit is connected to the input of the corresponding control pulses, the input of which is the corresponding power amplifier). i Fm.1 you} (od 2