SU1654657A1 - Device for measurement errors correction - Google Patents

Abstract

The invention relates to a measurement technique, and more specifically to devices that allow automatic correction of measurement errors, for example, temperature. The purpose of the invention is to improve the accuracy of correction in the automatic measurement mode. The device contains sources 1, 18 of stabilized and reference voltages, a primary sensor 3 of resistive type, a compensation element 4 in the form of a resistor, three switches 2, 5, 9, an amplifier 6, an analog-to-digital conversion unit 7, an indicator 10, an oscillator 11 cycles, frequency divider 12, clock pulse generator 13, reversible counter 14, comparison block 15, setpoint adjuster 16, reverse digital-tax converter 17, OR elements 20, 21 and two elements AND 8, 22. 1 Il.

Description

The invention relates to measuring technique, and more particularly to devices that automatically correct measurement errors, for example, temperature.

The aim of the invention is to increase the accuracy of correction in the automatic measurement mode.

The drawing shows a structural diagram of a device.

The device comprises a stabilized voltage source 1, a first switch 2, a resistive type primary sensor 3, a compensation element 4 in the form of a resistor, a second switch 5, an amplifier 6, an analog-to-digital conversion unit 7 in the form of a comparator 7ι, a 7g counter, a digital-to-analog converter (DAC) 7h, the second element And 8, the third switch 9, a digital indicator 10, an oscillator 11 cycles, a frequency divider 12, a clock generator 13, a reverse counter 14, a comparison unit 15, a setpoint adjuster 16, a digital-to-analog reverse reobrazovatel 17, reference voltage source 18 with a control attenuator 19, OR elements 20 and 21 and the first AND gate 22 are connected a certain way.

The source 1 is connected to the input of switch 2, which periodically connects it to resistive dividers with a working primary sensor 3 and a compensation element 4.The outputs of the working primary sensor 3 and compensation element 4 through a second switch 5 are alternately connected to the input of amplifier 6.

The switch 9 periodically (once in ten cycles) connects the output of the AND element 8 through the OR element 20 to the counting input of the reversible counter 14. The latter is connected to the block 15, which is connected to the digital setpoint adjuster 16, where the numbers corresponding to the compensation element connected to the circuit are entered 4. The temperature values measured by the exemplary primary sensor are set on the limb of the attenuator 19. The position of the attenuator allows you to adjust the progressive systematic error of the working primary sensor.

With a frequency set by the generator 11, the additive error due to the zero drift of the electronic measuring transducer is compensated. A frequency divider 12 (for example, one compensation cycle per ten workers) sets the frequency of compensation for the multiplicative error due to a change in the sensitivity of the electronic converter path. Compensation of the progressive systematic error of the primary sensor 3 is carried out manually in comparison with the standard primary sensor.

Compensation of the additive error is carried out for the first half of the period of one cycle, the second half of the cycle is used for the working measurement. In the first half of the cycle period, switch 2 disconnects the source 1 from the primary sensor 3, and switch 5 connects the signal of the primary sensor 3 corresponding to the zero level through the amplifier 6 to the input of the comparator 7ι. The output potential of the comparator gives the resolution of the count in the counter 7g, which is filled with pulses from the generator 13 clock cycles. As the counter fills up, the associated DAC 7z increases the voltage value at its output connected by the second input of the comparator 7ι until then. until it matches the zero level signal. At the time of comparison, the polarity of the voltage at the output of the comparator is reversed, which stops the pulse count in the 7g counter. A number is formed in the counter corresponding to the zero signal level. The element And 8 during this period of time is closed by the voltage of the generator 11. In the second half of the cycle period, switch 2 connects the source 1 to the primary sensor 3 and its output signal corresponding to the current value of the measured parameter through switch 5 and the amplifier 6 is fed to the input of the comparator 7). Since this voltage is greater than the voltage of the zero level, the comparator 7v returns to its original position and allows the counter to be counted 72;

At the same time, the second half of the cycle period, set by the generator 11, opens the And 8 element. The clock pulses are fed to the input of the 7g counter, continuing to fill it, and also go to the And 8 output. The 7g counter is filled with the pulses of the 13 generator until the output voltage DAC 7z does not equal the voltage at the first input of comparator 7ι. At this moment, the polarity of the voltage at the output of the comparator 7ι reverses, stops the counter 7g and closes the element And 8. During the opening time, the element And 8 passes to the output a number corresponding to the current value of the measured parameter and free from the additive error, since it is equal to the difference N = Mt - No, where No is a number corresponding to a zero initial signal level; Νι is the total number recorded in the counter for one cycle. The 7g counter is reset to zero, preparing for the next cycle.

The correction of the multiplicative error is performed for a separate compensation cycle, issued by the divider 12, for example, for every tenth pulse of the generator 11 cycles. During the operation of the compensation cycle, in addition to the indicated sequence of operations correcting the additive error, the switch 5 instead of the primary sensor 3 connects the compensation element 4 through the amplifier 6 to the input of the comparator 7ι, and the switch 10 connects the output of the AND 8 element instead of the indicator 10 through the OR element 20 to the input counter 14.

The counter 14 records the number N corresponding to the signal of the compensation element 4. This number is compared in block 15 with the number recorded in the digital dial 16, which is recorded in advance and corresponds to the nominal value of the compensation element 4 without taking into account the errors introduced by the electronic converter path.

Depending on the comparison result (more or less), a signal of the corresponding polarity arises at the input of block 15, or if the numbers are equal, there is no signal. The signal of block 15 sets the counting direction (forward or reverse) in the counter 14, as well as in the reverse DAC 17. The presence of a control signal at the output of the comparison block 15 provides a control signal at the output of the OR element 21, which opens the And element 22 for the passage of clock pulses of the generator 13 at the input of the counter 14 and the DAC 17.

For example, if the number recorded in the counter 14 is less than the setpoint in the setter 16, the control signals of the comparison unit provide a positive count of clock pulses in the counter 14 and the DAC 17. The pulse count continues until the numbers are equalized. At this moment, the control signal disappears at the output of block 15, then, accordingly, the And element 22 closes and the clock pulse flow stops through it. The number recorded in the DAC 17, controls the voltage of the source 18, connected through the attenuator 19 with the analog input of the DAC 7z. Similarly, the work of the scheme takes place with an inequality of the opposite sign.

Claims (1)

Claim A device for correcting measurement errors, containing a primary sensor of a resistive type, a compensation element in the form of a resistor, a reference voltage source, three switches, a series-connected amplifier and an analog-to-digital conversion unit, a voltage source, a digital indicator, characterized in that, in order to improve accuracy correction in the automatic measurement mode, two AND elements are introduced into it, two OR elements, setpoint adjusters, a reversible counter and a comparison unit connected in series, W The other group of inputs of which is connected to the outputs of the setpoint adjuster, a reversible digital-to-analog converter, the output of which is connected through a reference voltage source to the second input of the analog-to-digital conversion unit, the first and second control inputs - with the corresponding first and second control inputs of the reverse counter, the comparison unit and through the first OR element and the first AND element - with a counting input of a reversible digital-to-analog converter connected through a second OR element to a counting input o counter, a clock generator connected to another input of the first AND element, to the third input of the analog-to-digital conversion unit and to the first input of the second AND element, as well as a frequency divider and a cycle generator connected by the output to the control input of the first switch, to the fourth the input of the analog-to-digital conversion unit, to the second input of the second AND element, and through the frequency divider, to the control inputs of the second and third switches, while the voltage source is connected through the first switch a spruce tree with one terminal of the primary sensor and the compensation element, the other terminals of which are connected through the second switch to the input of the amplifier, the other input of the first switch is connected to the chassis bus, the output of the analog-to-digital conversion unit is connected through the second element And and the third switch with the input of the digital indicator, another the output of the third switch is connected to another input of the second OR element, and the digital-to-analog conversion unit is made in the form of a series-connected counter, digital-to-analog and the forming of the comparator, whose output is connected to the enable input is the output of the counter and digital to analog conversion unit, a first input of which is the second input of the comparator, the second input of the control input of the digital to analog converter, the third and fourth inputs of the respective counting inputs of the counter.