SU1597635A1 - Apparatus for checking force transducers - Google Patents

Abstract

The invention relates to a test apparatus and can be used to test strain gauge load transducers. The purpose of the invention is to improve the quality of verification of load transducers by reducing errors in determining their characteristics. The device contains a frame 1, an exemplary 2 and a calibrated 13 force-measuring transducers and an excitation unit 3 controlled by a regulator 12 sequentially installed in a power circuit. The control computer 4 is connected through an interface 5 to analog-digital converters (ADC) 6 and 7, a digital-to-analog converter (D / A converter) 8 and controllable voltage dividers (UDN) 9 and 10. Control unit 11 is turned on between the output of the DAC 8 and the input of the regulator 12. Switching the transfer coefficient of PDN 9 and 10 allows you to more fully meet the requirements of the calibration procedure by introducing a power circuit overload cycle without increasing the amplitude range of the ADC 6 and 7 and DAC 8. The ADC 6 enters information into the computer 4 from a verifiable load measuring device. converter 13 corresponding to the actual values of the reference points. 1 il.

Description

The invention relates to a test technique and can be used to calibrate force-measuring transducers having an electrical output signal, for example, strain gauges.

The purpose of the invention is to improve the quality of verification of force-measuring transducers by reducing errors in the determination of their characteristics.

 The drawing shows a block diagram of a device for calibrating force-measuring transducers.

A device for calibrating force-measuring transducers contains a frame 1, an exemplary force-measuring transducer 2, a power excitation unit 3 controlling a computer 4, an interface 5, the first 6 and second 7 analog-to-digital converters, a digital-to-analog converter 8, the first 9 and the second 10 controlled voltage dividers, a control unit 11, a regulator 12 and a transducer to be calibrated 13.

The device works as follows.

in a way.

The device is installed

a rotatable force-measuring converter 13, the output of which is connected to the first input of the second depot 10.

Before a triple load of the verified load measuring transducer 13, it is overloaded for at least 5 minutes with a load that exceeds the nominal load by 25%. For this, the control computer 4 generates a command that, through the interface 5, in the form of a control voltage, arrives at the second control inputs of the voltage dividers 9 and 10 and switches their transmission coefficients from 1 to 0.8. As a result, the signals from the outputs of the model

and verified load transducers 2 and 13 are 1.25 times. Then the computer 4 begins to earn control codes, which through the interface 5 are fed to the input of the digital-to-digital converter 8, which generates the load command signal. This signal changes from a minimum level to a maximum corresponding to the nominal load I equal to. the upper limit of the amplitudes of the range of the digital-to-analog j converter 8 and the analog-digital converters 6 and 7, and then from the maximum to the minimum.

The reference signal and the 1.25-fold divided feedback signal from the reference load transducer 2 are fed to the control unit 11, in which the error signal is generated from them, which, after amplification, arrives at the controller 12 and controls the excitation of the load. Simultaneously with the loading on the commands of the computer 4, arriving through the unit 5 of the interface to the second inputs of the start of the analog-digital converters 6 and 7, they are periodically started. The results of the analog-digital conversion of the output voltages reduced by 1.25 times of the force-measuring converters 2 and 13 through the interface 5 are entered in the form of codes into the computer 4, which performs the load control. Thereby, the cycle of the overload of the verified load-measuring converter to .. the load is 25% higher. Nominal, without increasing the amplitude range of digital-analog and analog-digital converters of the device. After the end of the cycle of overload on the command of the computer 4, the transfer coefficient of the dividers 9 and 10 of the voltage again switches to 1.

After overloading, in order to determine the characteristics of a calibrated load transducer, 13, the device performs a triple load in forward and reverse order with the measurement of its output signal at the load stages corresponding to the reference points of the grading characteristic. In order to ensure that the readings of the calibrated transducer 13 are metrologically correct, a main one-sided approach to the reference points is required without overshooting and oscillations around them. In the device, this condition is fulfilled without slowing down the load and the formation of load areas in the vicinity of the reference points due to the smooth continuous change of the load from the minimum value to the maximum and in the opposite direction. The control computer 4 generates control codes that continuously change at a given rate and quantization step. Proceeding through the interface 5 to the input of the digital-to-analog converter 8, these codes are converted into a continuously varying load reference signal. The smoothness of the transitions between the quantization levels of the signal is ensured by the inclusion of a smoothing capacitor of an insignificant capacitance (not shown) on the code converter 8. In the process of loading the computer 4 through the interface 5, the unit performs periodic simultaneous launch of analog-digital converters 6 and 7 sequential in time, inputting their output codes to control the loading and adjust the rate of change of the control codes depending on the amount of mismatch between the reference signal and the reverse signal connection. When the load approaches the next reference point without slowing down the loading of the computer 4, it increases the frequency of starting analog-digital converters 6 and 7 to the maximum possible. At the same time, in order to increase the speed of input and processing of information, the computer 4 only enters and analyzes the output codes of an analog digital converter 7, which converts the output signal of an exemplary force-measuring converter 2 When the analysis of these codes results in the equality of the next reference point, the computer 4 introduces the corresponding

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5976356

The output code of the analog-to-digital converter 6. This code is the result of the analog-digital conversion of the value of the output signal of the calibrated load-measuring converter 13, which corresponds to the exact equality of the excited load and the reference point reached. Due to the Q simultaneous start-up of analog-digital converters 6 and 7 and the identity of their static and dynamic properties, the effect on the verification results of their static

J5 systematic and dynamic errors.

In the study of the stability of indications of a verified load-measuring converter 13 with a continuous effect of a nominal load of the computer 4 v, a fixed control code corresponding to the 1st is output to the digital-to-analog converter 8 during the regulated time.

25 nominal load and periodically enters the output codes of analog-to-digital converters 6 and 7.

Measuring information is accumulated in the memory.

The computer 30 and 4 after the termination of the test loads of the verified force measuring transducer 13 is processed by it according to GOST 15077-78. In this case, the systematic component of the error and the standard deviation of the random component of the error are calculated, the hysteresis and the non-linearity are determined, the variations of the initial and working values are calculated

The Qth transformation coefficients, when the temperature varies and the load eccentricity is present, is determined. drift readings converted under continuous load. In this case, the resolutions of the computer 4 determine the class (category) of the accuracy of the inverted load transducer 13, and the results of the verification are in the form of a verification protocol indicating

50 listed characteristics.

35

55

Claims (1)

Claims of the invention: A device for calibrating force-measuring transducers containing a frame, a power-excitation unit sequentially installed in a power circuit, a tunable and exemplary force measuring transducer, a interface unit, a control computer, a digital-analogue converter, a control unit, a regulator An analog-to-digital converter, the output of which is connected to the first input of the power supply unit, the second input of which is connected to the input-output bus of the control computer, and the first output is connected to the input of the digital-analog The converter, the output of which is connected to the first input of the control unit, the output of which is connected to the input of the regulator, the output connected to the power excitation unit, is characterized in that, for the purpose of quality, two controllable voltage dividers are introduced into it and the second analogue a digital converter, the first input of which is connected to the second input of the control unit, and the output is connected to the third input of the interface unit, the second output of which is connected to the first inputs of the first and second controlled voltage dividers, the second the inputs of which are connected respectively to the outputs of the reference and verified load-measuring transducers, and the outputs are connected respectively to the first inputs of the first and second analog-to-digital converters, the second inputs of which are connected to the third output of the interface block.