SU674214A1 - Frequency-output measuring converter - Google Patents

Description

a recharger and a measuring amplifier whose input is connected to one of the terminals for connecting the measured quadrupole, one branch of the selective quadrupole contains series-connected one resistor and a capacitor connected to the transmitter ground line, and the other branch of the four-port selective side contains another resistor connected to one switch the capacitor, the other plate of which through the source-drain channel of the field-effect transistor is connected to the earth bus of the meter, while the first water quadripole selectively connected to the other terminal for connecting the measuring quadrupole and through a limiting resistor - to the output of the measuring amplifier.

The drawing shows a structural electrical converter circuit.

The converter contains an RC oscillator i, covered by a circuit of positive (controlled) and negative (tracking) feedback. ; -,

The positive frequency feedback circuit consists of a measuring quadripole 2, an amplifier 3, a limiting resistor 4, a resistor 5 and a capacitor 6. The negative (following) reverse circuit consists of an adjustable element — a field-effect transistor 7, combined with the body the converter is automatically converted on the gate by an automatic gain control unit 8, a capacitor 9 and a resistor 10.

Resistors 5 and 10, capacitors 6 and 9, field effect transistor 7 are electoral 1st quadrupole And

The converter works as follows.

The generator 1 feeds the measuring quadrupole 2, the output of which is proportional to the electrical circuit being transformed or changed, is amplified by the amplifier 3 and is introduced into the circuit of adjustable positive feedback.

The effect of the input voltage is equivalent to changing the limiting resistor 4. When changing the limiting-resistor 4, the resistance of the field-effect transistor 7 automatically changes the ho of the circuit with the following communication pattern by the same amount, since the integral quadrupole I (the bridge essentially) must be constantly in the state of quasi-equilibrium

Condition quasi-equilibrium:

 6

(i)

t with:

5 4 -S where R7 is the drain-source channel resistance of the field-effect transistor 7 in the controlled resistance mode;

R 4. RS. Rio. Sat and C, are the resistances of resistors 4, 5, 10 and capacitors 6 and 9, respectively.

In this case, the frequency converter will be equal to:

,

t

Where

the transfer coefficient is measuring

th quadrupole 2; gain of measuring amplifier 3;

.R:

1 / 2ЛК,

) Sbc9

 IVp.

R4., C

- initial value at.

From the expression (2) and (3) it can be seen that the frequency at the output of the converter is linearly connected with the conversion parameter.

In this way, the transmitter increases the measurement accuracy by increasing noise immunity and reducing non-linear distortion.

Claims (2)

1. USSR author's certificate number 226019, cl. G 01 R 27/16, 1966. 2. USSR author's certificate number 409367, cl. H 03 K 13/20, 1972.