SU691766A2 - Extremum modulating digital bridge circuit - Google Patents

Description

(54) DIGITAL EXTREME MODULATION BRIDGE

The invention relates to the field of measuring equipment and is intended to measure various electrical parameters, such as capacitance, inductance, active resistance, and. etc.

According to the main author. St. No. 595675 is known for a digital extra small modulation bridge comprising a power generator, a bridge circuit, a detector, a control unit, a modulator, a reversible counter, keys, a reverse trigger, a digital readout block, and OR-NOT, OR, and 1 elements.

Due to the quantization error, its accuracy is low.

The aim of the invention is to improve the accuracy of the device with a constant number of sample elements.

To do this, an extreme modulation bridge containing a generator, supplying a bridge circuit, the output of which is connected through the detector to the information inputs of the keys, the output of the first key is connected to the input of the reverse trigger, the output of which is connected to the inputs of the reversible counter and the modulator, the other input of the modulator is connected And, OR, OR, and NOT tapes are entered to one of the outputs of the control unit, the second output of which is connected to the control inputs of the keys, the outputs of the modulator and the reversible counter, and The second key is connected to the first inputs of the OR and OR-HEj elements, the second input of the last element is connected to the output of the first key, and the output is connected to the input of the AND element, the second input of which is connected to the output of the reverse trigger, and the third input to the second input of the control unit, the output of the AND element is connected to the second input of the OR element, and the output of the latter is connected to the counting input of the reversible counter; in addition, it is equipped with a digital reading unit, an additional discharge trigger and two additional AND elements, and the second output of the block control is connected to the first inputs of the additional elements AND, the second input of the first of which is connected to the direct output of the element OR NOT, the inverse output of which is connected to the second input of another additional element AND, the output of which is connected to one input of the additional discharge trigger, another input . Secondly, it is connected to the output of the first additional element I, and the output to the second input of the digital reading unit, the first input of which is connected to the output of the reversible counter.

FIG. 1 shows a structural electrical circuit of the proposed device, FIG. Figure 2 shows the dependence of the output voltage module of the bridge on the change in the adjustable shoulder for the case in which the true equilibrium point of the bridge is exactly in the middle of the quantum.

The device contains a generator 1, a bridge circuit 2, a detector 3, a control unit 4, a modulator 5, a reversing counter 6, keys 7 and 8, a reverse trigger 9, elements OR NOT 1O, 11, OR 12, a digital reading unit 13, additional trigger trigger yes 14, elements I 15, 16 ..

The device operation is as follows.

The generator 1 feeds the bridge circuit 2. The modulator 5 produces a periodic change in the adjustable arm of the bridge circuit 2 by one step. The direction of the modulation changes and the direction of the counting of the reversible counter 6 is determined by the state of the reverse trigger 9 (the potential at the output of the reverse trigger 9 corresponds to the counting down, and the lack of potential to the forward counting of the reverse counter 6).

The bending of the modulated output voltage of the bridge circuit 2 is extracted by the detector 3 and is supplied as a control signal to the inputs 7 and 8.

If the counting direction of the reversible counter does not correspond to equilibrium, then a positive pulse appears at the output of detector 3, which opens key 7, after which the pulse from the second output of control unit 4, the passage through it, goes to the input of the reverse trigger 9 and changes it condition. After that, at the output of the detector until the moment of equilibrium, negative pulses are detected in the vehicle, which open the key 8. And

The pulses from the second output of the control unit through the key 8 and the element OR 12 are fed to the counting input of the reversing counter 6, which changes the value of the adjustable arm of the bridge circuit 2. When receiving equilibrium at the detector output, positive counts stop and only the state the reverse trigger periodically changes.

If there are no modulation pulses at the detector output, for example, when the true equilibrium point A is in the middle of the quantum (Fig. 2), the keys 7 and 8 are locked, and a potential appears at the output of the OR-NOT element.

In this case, the output pulses of the control unit, depending on the state of the reverse trigger, when counting down, go through the elements AND 11 and OR 12 to the input of the reversible counter, but not directly. Therefore, in the absence of modular impulses at the output of the detector 3, the bridge can move only into one cTopoiiy - from point 4 to point 3 (Fig. 2).

Consequently, at the mid points of the quites, with forward and reverse moves, the readings of the reversible counter will correspond only to their lower bounds. At the same time, since the potential output of the OR-NOT unit is potential, the pulse from the second output of the control unit 4 passes through the element 15 and translates the trigger 14 into one state, which on the digital reading unit 13 additionally displays a figure corresponding to half the weight younger category Consequently, the reading of the digital reading unit 13 will also correspond to the middle of this quantum, as a result of which the measurement accuracy is increased. While there are no modulation pulses at the output of the detector 3, trigger 14 is in the unit state. At close values of the measured parameter to the quantum boundaries, the modulation pulses reappear, and a potential appears at the reverse output of the element OR-NOT 10, resulting in the pulses from the second output of the control unit, the passage through AND 16, bring it to the zero state. The reading of the digital reading unit 13 in this case corresponds to one of the boundaries of the quantum.

In the known device, there is a strict requirement for the sensitivity of the detector. To ensure that the error

bwjia equal to half a quantum, it requires a detector with a zero sensitivity threshold (t, that is, infinitely sensitive). In the proposed device, such accuracy is ensured at a sensitivity threshold equal to one quantum, and at lower values, its accuracy and measurement of the proposed device will be higher than that of the known one.

Thus, in the proposed device, the requirement for the sensitivity of the detector is reduced, and the measurement accuracy is increased without increasing the number of bit exemplary elements.

Claims (1)

1. USSR author's certificate number 595675. class. G 01 R 17/10,. 08/06/76. 1 I, I S s -I } -. I -one WBiHmM FIG. g