SU1698825A1 - Voltmeter inner resistance tester - Google Patents

Abstract

The invention relates to a measuring technique and can be used in systems for automated or automatic calibration of electrical measuring instruments. The device contains a power supply 1, a resistor 2, keys 3-1 b, a capacitor 7, analog storage units 8 and 9, an exemplary controlled magazine. 10 resistances, a voltmeter 11 under study, a voltmeter arrow tracking unit 12 and a control unit 13. The device allows various voltmeters to be turned with increased accuracy, has a simpler structure and increased productivity. 1 hp f-ly, 2 ill. J

Description

The invention relates to measuring equipment and can be used in systems of automated or automatic calibration of electrical meters.

The purpose of the invention is to improve the accuracy and simplification of the device.

Figure 1 shows a structural diagram of a device for measuring the internal resistance of a voltmeter; figure 2 is an embodiment of a control device included in figure 1.

A device for measuring the internal resistance of a voltmeter (Fig. 1) contains a power source 1, a resistor 2. Keys 3-6, a capacitor 7, the first 8 and second 9 analog memory blocks, an exemplary controlled magazine 10, a tested voltmeter 11, an arrow tracking unit 12 voltmeter (converter), control unit 13. The power source 1 is connected in series with a resistor 2, to which the input of the first analogue storage unit (АЗУ) 8 is connected, as well as the first key 3 and capacitor 7, connected in parallel and connected to a common point, and the input of the АЗУ 9 and the input of the second are connected to the output of the first АЗУ 8 a key 4, the output of which is connected to the output of the third key 5 and the inputs of an exemplary controlled resistance store 10 and a key 6 connected in parallel to it. One input terminal of the voltmeter 11 under study is connected to the output of the fourth key 6, the second terminal of which is connected to the position of the arrow of the voltmeter 11 is controlled by the unit 12 tracking the arrow of the voltmeter. The output of the tracking unit 12 is connected to the input of the control unit 13. The control inputs of the keys 3-6, AZU 8 and 9 and the model store 10 resistance are connected to the first to seventh outputs of the control unit 13, respectively.

The control unit 13 contains two generators - a clock generator 14 and a counting pulse generator 15, a key 16, a clock counter 17 and a magazine control counter 18, a start trigger 19, an OR 20 circuit, three AND 21-23 circuits, two inverters 24 and 25, two shapers 26 and 27 and a register 28 of the result code of the internal resistance of the tested voltmeter.

The device operates as follows.

In the initial state, the keys 3, 4 and 6 are closed, and the key 5 is open, the AZU 8 and 9 transmit signals from input to output with a conversion coefficient equal to 1. Under the action of the control unit 13, the resistance of the exemplary managed store is set to maximum. The voltage at the capacitor 7, and therefore at the output of the first AZU 8, at the inputs and outputs of the keys 4-6 and voltmeter 11, is close to zero.

When the Start signal arrives at the control unit 13 (first cycle), it opens the first switch 3 and the voltage across the capacitor 7 starts to increase smoothly. When the arrow of the voltmeter 11 approaches a certain selected point, the converter 12 is activated, which, acting on the input of the control unit 13, first causes the voltage of the capacitor 7 to be memorized at the first AZU 8, then the voltage is stored at the second AZU 9, after which the AZU 9 is connected so that the voltage at the output of the second AZU 9 was summed with the output voltage of the first AZU 8, i.e. at the output of the AZU 9, the voltage is equal to twice the voltage at the output of the AZU 8. In addition, the keys 4 and 6 open, and the key 5 closes. Since the maximum resistance of the magazine 10 is selected significantly larger than the internal resistance of the voltmeter 11. the reading of the voltmeter 11 decreases.

In the second clock, the seventh output of the control unit 13 acts on the control input of the resistance store 10 and reduces its resistance. In this case, the reading of the voltmeter 11 (V) increases. When the arrow reaches the position (mark) at which the converter 12 is activated, the control unit 13 ceases to affect the control input of the store 10. This completes the operation of the device. The internal resistance of the voltmeter 11 is equal to the resistance of the magazine 10.

At the time of the first countdown, a current Ινι flows through a controlled voltmeter

Iv, (1) where Rv is the internal resistance of the voltmeter.

At the moment of the second reference, a current IV2 flows through the voltmeter where Rm is the resistance value of the model resistance magazine, at which the needle is set in the same position as in the first reference.

Since both readings are performed at the same arrow position, obviously 'lvi = lv _a . (3) therefore

U 2U and get Rv = Rm. R v Rv + R m (4) (5)

The resulting equality indicates that the definition of resistance is will. A meter using this device does not require calculations. Since the readings were made at the same point on the scale, there is an increase in the measurement accuracy, and the number of precision elements used is significantly reduced compared with the prototype, there remains only one precision element, an exemplary resistance store.

In the initial state, under the influence of the trigger 19, the key 16 of the control unit is closed, and the counter 17 is reset. The signal from its output goes to the first output of the control device and holds the key 3 in the closed state (Fig. 1), through the OR 20 circuit it enters the second and fourth outputs (closes the keys, Fig. 1) and through the inverter 25 it goes to the third output ( opens the key 5, figure 1). The second output of the counter 17 holds in a single state the triggers of the counter 18 (the maximum code is set at its output), and does not pass the pulses of the generator 15 through the circuit And 22.

When the Start signal arrives, trigger 19 is thrown, the reset signal is not supplied to counter 17, and generator 14 is connected to its counter input via key 16, under the influence of pulses of which counter 17 changes its state. In this case, the control action at the first output of the control unit 13 is removed. The signal from the single output of the counter 17 enters through the OR circuit 20 to the second and fourth outputs (keys 4 and 6 remain closed, Fig. 1) and through the inverter 25 to the third output (key 5 remains open). Also prepared for work circuit And 21, which expects the arrival of a pulse from the Converter 12 (figure 1). When this pulse arrives, it goes through the And 21 circuit to a shaper 26, which generates a signal at the fifth output, which ensures that the voltage across the capacitor 7 of the AZU 8 is stored (Fig. 1). After the process of memorization in the AZU 8, a similar memorization is performed in the AZU 9 (figure 1) under the influence of the signal of the shaper 27.

After the end of the first clock, the counter 17 under the influence of the pulse of the generator 14 again measures its state. In this case, the state of the first output of the control unit 13 does not change (key 3 remains open, Fig. 1), signals do not arrive at the inputs of the OR circuit 20 (keys 4 and 6 open, Fig. 1), and accordingly, key 5 is closed under the action of inverter 25 The second output of the clock counter 17 allows the pulses of the generator 15 to pass through the circuit AND 22 to the counter 18. Since the resistance of the exemplary controlled magazine 10 is selected to exceed the internal resistance of the voltmeter 11, the signal of the converter 12 inverted by the inverter 24 does not prevent the passage NIJ pulse generator 15 to counter 18, which is included in the subtraction. Under the influence of the pulses of the generator 15, the control action at the seventh output causes a decrease in the resistance of the magazine 10 and thereby an increase in the reading of the voltmeter 11. When the arrow reaches the position (mark) at which the converter 12 is triggered, a pulse is transmitted to the control unit 13, which prevents the passage of pulses through the inverter 24 'generator 15 through the circuit And 22 to the counter 18, recording the achievement of the resistance of the magazine 10 equal to the resistance of the voltmeter 11. The same pulse passes through the circuit And 23 and records a counter 18 to the register 28 results, but also resets flip-flop 19. This operation of the device ends. Trigger 19 resets counter 17, returning the circuit to its original state. The code at the output of the register 28 corresponds to the internal resistance of the voltmeter 11.

The proposed device allows you to automate the measurement process, increase productivity.

Claims (2)

Claim 1. A device for measuring the internal resistance of a voltmeter, containing a power source with a series-connected resistor, as well as an exemplary controlled resistance store, in parallel with which the first key is connected, the output is the measurement object, and the outputs are the outputs of the second and third keys, characterized in that , in order to improve accuracy and simplify the device, a tracking unit is installed in it, installed on the same optical line with the measurement object, the fourth key is connected in parallel and connected to a common point and the capacitor, the first and second analog storage units, the outputs of which are connected to the information inputs of the second and third keys, respectively, the input of the first analog storage unit connected to the connection point of the fourth key, capacitor and resistor, the input of the second analog storage unit connected to the output of the first 5 analog storage unit, and the output of the tracking unit is connected to the input of the control unit, the first and fourth outputs of the control unit are connected to the control inputs of the fourth, second, of the third and first keys, respectively, the fifth and sixth outputs are connected to the control inputs of the first and second analog storage units, and the seventh to the controlled resistance store. fifteen 2. The device according to claim 1, with the fact that the control unit of which contains a clock generator, the output of which is connected via a key to the C-input of clock 20 of the counter, the R-input of which is connected to the control input the key and the output of the start trigger, the R-input of which is connected to the C-input of the result register, the first and second outputs of the clock counter are connected to the inputs of the OR element, the output of which is the second and fourth outputs of the block, and also through the second inverter is connected to the third output of the block, the second output of the clock counter is connected to the second input of the first element And, the third input of which 10 is connected to the counting pulse generator, and whose output through the first driver is connected to the fifth output of the unit, which is connected to the sixth output through the second driver, the first input of the AND element is connected through the first inverter to the first input of the second element And the first input of the third element And the second input of which is connected to the second input of the second element And and the S-input of the store control counter, the outputs of which are the seventh output of the unit and are connected to the D-input As a result, the C-input of which is connected to the output of the third element I.