SU1401400A1 - Device for tolerance check of resistors - Google Patents

Abstract

The invention can be used, in particular, to control the insulation resistance of electrical components. The device for tolerance control of resistances includes a power supply 3, a current stabilizer 4, resistors 6-9, an operational amplifier 2 regulating a field-effect transistor 1, diodes 10 and 11, terminals 12 and 13 for connecting a controlled resistance, the measuring voltage source 5. The functionality of the device is enhanced by the ability to control insulation resistance. 1 il.

Description

SS

(L

four

R

four

The invention relates to the field of electrical measurements and can be used to control the resistance of radio-radio products, in particular, insulation resistance.

The purpose of the invention is to enhance the functionality by providing the ability to control the insulation resistance.

The drawing shows a device for tolerance control of resistances.

The device contains a field-effect transistor 1, an operational amplifier 2, a power supply 3, a current stabilizer 4, a measuring voltage source 5, the first 6, the second 7, the third 8 and the fourth 9 resistors, the first 10 and second 11 diodes, the first 12 and second 13 terminals to connect a monitored resistance and indicator 14.

The device works as follows.

At the midpoint of the divider formed by resistors 6 and 7, relative to the total width of the device, a voltage Uo is generated, which is fed to the inverting input of operational amplifier 2. To the non-inverting input of amplifier 2, which is connected to the controlled (tested) resistance RX through a resistor 8 and terminal 12 A relatively common voltage is applied voltage U, -. When the amplifier 2 generates a control signal of the field-effect transistor 1, which corresponds to the channel enrichment mode, and when Co: Lloc - the cutoff current drain mode.

The current Ion of the stabilizer 4 determines the threshold (the resistance value R, at which the device abruptly changes its state (more or less Rwn). The current L b is determined by the formula

I and ° + U

1st ---

Cdop

Through the circuit + ipit, the current stabilizer 4, the drain-source resistance of transistor 1, the resistor 9, R, -UHSM current flows, under the action of which a voltage U is formed.

When the inequality is fulfilled, the voltage at the output terminal of the device is more negative due to the level of limiting the voltage of the negative polarity of the operational amplifier 2, and the transistor 1 is saturated. To prevent the transistor 1 and the operational amplifier 2 from failing due to the impact of a high UHSM voltage, near zero, diode limiters are applied on resistors 8 and 9 and diodes 10 and 11. As a result, even at Rx O, the voltage Uoc practically zero.

If .oii, then transistor 1 operates in active mode, increasing its resistance so much that the voltage on stabilizer 4 is not sufficient to stabilize the current. As a result

0

five

0

five

0

five

0

50

five

the current through the resistance R is regulated by the transistor, and, due to the high gain of the operational amplifier 2, the equality Uo Uoc is maintained, i.e. Ux Uo + UH3M. The voltage on the indicator 14 is positive and close to the cut-off voltage of the drain current (to the threshold voltage of the transistor with an induced channel). As RX decreases, the current of the transistor increases to the value of Ln and cannot be changed further due to the functioning of current stabilizer 4. This leads to a malfunction of the feedback, a decrease in the voltage Uoc and an abrupt change in the voltage on the indicator 14 to a large negative value.

Thus, by setting the value of Ion of the current stabilizer 4, it is possible to set the values of Riwn such that when Rx Rdop, the voltage on the indicator 14 is positive, and when R; R; ioii is negative. The width of the transition zone is determined by the gain of the op-amp 2.

The use of an additional measuring voltage source UHBM allows the voltage U to be increased to the values necessary to control the insulation resistance of the products without increasing the voltage acting on the control transistor, more than LJiiMT.

Claims (1)

Invention Formula A device for tolerance control of resistances, containing a power source, a current stabilizer, first and second resistors, an operational amplifier and a control field-effect transistor, the source of which is connected via a current stabilizer to the positive terminal of the power source, the negative terminal of which is connected to the total thickness of the device, is connected to the indicator and the output of the operational amplifier, the inverting input of which is connected through the first resistor to the positive terminal, and through the second resistor - the negative terminal One power source, characterized in that, in order to extend the functionality by providing the ability to monitor the insulation resistance, the third and fourth resistors, the first and second diodes and the measuring voltage source are introduced, the positive terminal of which is connected to the common bus, the negative terminal is connected to the first terminal for connecting the monitored resistance, and the second terminal for connecting the monitored resistance is connected via a third resistor to the non-inverting input ohm operational amplifier and through the fourth resistor - with the drain of the regulating field-effect transistor, and between the drain 1401400 34 regulating field-effect transistor and the common length are connected, respectively, by the front bus, as well as between the non-inverted and the second diodes, the anodes of which are connected by the connecting input of the operational amplifier and dinene with the total thickness of the device.