SU1570878A1 - Method and apparatus for measuring contact resistance in cutting tool-part pair - Google Patents

Abstract

The invention relates to a measurement technique and can be used to measure the parameters of a metal cutting process. The purpose of the invention is to increase accuracy by eliminating the influence of thermoEMF on the measurement result. To do this, connect a source of direct voltage to a pair of instrument-parts, measure the resistance, make an additional measurement of the resulting circuit with the source of a constant voltage connected with the opposite polarity, and calculate the value of the transient resistance by the average of the two mentioned measurements. Seven keys, four delay blocks, a second constant voltage source, a trigger, an adder, a memory, a divider, two single-oscillators, a toggle switch, and a filter are added to the device. 2 sp.f-ly, 1 ill.

Description

The invention relates to a measurement technique and can be used to measure the parameters of a metal cutting process.

The purpose of the invention is to improve accuracy by eliminating the influence of thermo-emf on the measurement result.

The drawing shows a functional diagram of the proposed device.

The device contains the main source 1 of constant voltage, which by the first pole through current limiting resistance 2, ammeter 3, as well as the first and second keys 4 and 5 are connected respectively to part 6 and tool 7, and the second pole through the first contact 8 of the dual toggle switch, as well as the third and fourth keys 9 and 10 are connected to the part 6 and the tool 7 in the same way as the first pole; a voltmeter 11 connected in parallel to the part 6 and the tool 7 between the keys 4, 5 and the ammeter 3 and between the keys 9, 10

 and contact 9, a smoothing filter 12, switched between resistance 2 and ammeter 3. and between contact 8 and the connection point of the voltmeter 11 to the circuit section connecting contact 8 with keys 9 and 10, adder 13, which is the first input through the memory 14 and the fifth key 15, the second input through the sixth key 16 is connected to the output of a voltmeter 11 and the output is connected to the first input of the divider 17; the second constant voltage source 18, which is connected via the second pin 19 of the dual toggle switch to the inputs of the first and second delay blocks 20 and 21 and the first one-shot 22, the trigger 23; The first input is connected with the output of the first one-shot 22, the second input through the second one-shot 24 is connected to the output of the first block 20 of the delay, the single output is connected directly to the control inputs of keys 5 and 9 and through the third block 25 of the delay connected to the MSP

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key input 16 and memory device 14, and the zero output is connected directly to the control inputs of keys 4 and 10 and through the fourth delay block 26 to the control input of key 15. In addition, the circuit contains the seventh key 27 connected between the output of the divider 17 and the output of the device, the second input of the divider 17 is connected to the output of ammeter 3, and the control input of the key 27 is connected to the output of the delay unit 21. Note that ammeter 3 and voltmeter 11 are digital, fifth, sixth, and seventh keys 15, 16, and 27 are logic circuits on AND connected in parallel, memory 14 is made on RS flip-flops, keys 4, 5, 9, and 10 are electromagnetic relays with amplifiers. At the same time, the current limiting resistance 2 is at least an order of magnitude greater than the measured transient resistance, divider 17 has a division factor equal to twice the output signal of ammeter 3, the input signal delay time by blocks 25 and 26 exceeds the duration of transients when keys 4 are triggered, 5, 9 and 10 and the time required by the voltmeter 11 for one measurement, the delay time by unit 20 exceeds the signal delay time by unit 26 and the time required for recording information in memory ayuschee unit 14 and delay unit 21 the signal duration exceeds the duration of the delay units 20 and 25, the time required to actuate switch 16 and poll the memory 14 as well as the response time of the adder 13 and the divider 17 taken together

Before using the device, the dual toggle switch is turned off, contacts 8 and 19 are open, trigger 23 is in the initial position indicated in the figure, and the part 6 is machined by tool 7.

When the toggle switch is turned on, pins 8 and 19 are closed, the source 18 receives a signal to the delay blocks 20 and 21 and a single vibrator 22. The latter issues a pulse to the first input of the trigger 23 and transfers it. At the second trigger output, the signal "I" appears, which turns on the keys 4 and 10 and is delayed in the delay block 26. At the same time, the voltage from source 1 through resistance 2, ammeter 3, pin 8 and keys 4 and 10 is fed to a pair of cutting tools 7 - part 6. Voltmeter 11 measures the voltage drop at a transient resistance in a pair of tool parts with a positive ( negative) additive thermo-EMF cutting. At the end of the measurement, the delay block 26 passes the signal to the key 15 and the measurement result is stored in the memory 14. At this point, the signal delay time by the block 20 expires. This block outputs the signal to the one-shot 24, and the latter switches the trigger 23 to the initial position. The "1" signal disappears from the second trigger output and appears at its first output. He enters keys 5 and 9 and turns them on. Keys 4, 10, and 15 are turned off. As a result, the pair of instrument-part is connected to the voltmeter 11

and a power source 1 with other poles and a voltmeter 11 measures the voltage drop across a transient resistance in a pair of instrument-part with a negative (positive) addition of thermo-emf. Since key 15 is already closed, the measurement result is not stored in the memory, but by the time the measurement ends, the delay unit 25 passes the turn-on signal to the key 16 and the interrogation signal to the memory 14. Under the influence of this signal, the current measurement result from the voltmeter 11 and the previous result device 14 enters adder 13 and stacks. With the addition of positive and negative additives thermo-EMF

5 are mutually destroyed and the doubled value of the voltage drop across the measured resistance is obtained in a "pure form." Further, this value goes to divider 17, where the signal from the output of ammeter 3 has already arrived. Since the current detected

0 with an ammeter, practically depends only on resistance 2, thermo-emf does not affect it. The divider 17 divides the output signal of the adder 13 by twice the output signal of the ammeter 3, after which its output will show 5 s signal R, which characterizes the value of the measured transient resistance in a pair of cutting tool-part. By the time the division ends, the delay block 20 passes the incoming to it earlier

The Q signal from pin 19 to key 27, the latter in turn, passes a signal of the resistance value to the output of the device.

Claims (2)

Invention Formula 5 1- Method of measuring transient resistance. A pair of cutting tool part consisting in connecting a source of direct voltage between the tool and the part is measured by the resistance of the resulting circuit, which is distinguished by the fact that, in order to improve the accuracy, an additional measurement of the resistance that is formed the polarity of the constant voltage source, and the magnitude of the transition resistance is determined by the average value of the two mentioned measurements. 2. A device for measuring the transient resistance in a pair of cutting tool-part, containing the first constant voltage source connected to the pair of cutting tool-part through a current-limiting resistance and an ammeter, and a voltmeter connected in parallel to the tool and parts, characterized in that In order to improve the measurement accuracy, the device is additionally equipped with a toggle switch, a second constant voltage source, four delay blocks, two one-oscillators, a divider, a totalizer that stores the device Real estate, a trigger, seven keys, a filter, the second source of constant voltage being connected by the same pole to the first source of constant voltage and the first contact of the toggle switch, the second pole of the second source of constant voltage connected to the second contact of the toggle switch, the second contact The toggle switch is connected to the inputs of the first and second delay blocks and the input of the first one-shot, the output of which is connected to the first input of the trigger, the output of the first delay block through the second single-vibration switch is connected to the second input of the trigger EPA, the zero output of which is connected to the control input of the first switch, the trigger output unit connected to the control inputs of the second and third keys, the outputs of the first and third key are combined and connected to the workpiece, the control input of the fourth key is combined with zero output of the trigger; outputs of the second and fourth keys are combined and connected to the instrument; input of the third delay unit is connected to the single output of the trigger; inputs of the fifth and sixth keys are combined and connected to the output of the voltmeter; the control input of the first key is connected through the fourth delay unit to the control input of the fifth key., - the output of which is connected to the first input of the storage device, the second input of the storage device is connected to the combined control input of the sixth key and the output of the third block delays, the output of the sixth key is connected to the first input of the adder, the second input of which is connected to the output of the storage device, the first input of the divider is connected to the output of the ammeter, the second input is shared with the output of the adder, the output of the divider is connected to the input of the seventh key, the control input of which is connected with the output of the second delay unit, the output of the seventh key is the output of the device, the smoothing filter is the first contact connected between the resistance and the ammeter, and the second contact between the first contact of the toggle switch, volume the inputs of the third and fourth keys, the inputs of the first and second keys are combined and connected to the terminals of the ammeter and voltmeter.