SU789839A1 - Digital integrating voltmeter - Google Patents

Description

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 The ejection refers to measurement technology and is intended for use in digital devices or information and measurement systems.

Known digital voltmeter push-pull integration. one.

The lack of a voltmeter lies in the low accuracy in the initial part of the instrument scale due to the nonlinear nature of the instrument scale, which is due to the time delays in the operation of the units and instrument components (integrator, comparator, control logic, keys, etc.) and the presence of residual voltages and currents clkchey.

A digital integrating volt lehr of a push-pull integrating is known, the block diagram of which includes an analog input, a voltage converter into a current, a reference current source connected via a switch to a current adder, and a series-connected integrator, comparator, and control logic unit. , as well as 25 digital counter and synchronization unit {2}.

The disadvantage of a voltmeter is the presence of a nonlinearity zone (dead zone) near zero, which reduces the measurement accuracy. thirty

The purpose of the invention is to improve the accuracy of voltage measurement.

The goal is achieved in that a digital integrating voltmeter containing a series-connected integrator, a zero level comparator and a control logic block, a source, a reference voltage, connected through a switch to the integrator input, a high-frequency pulse generator connected to the first input of the control logic block, the output of which is connected via a digital counter with a reading device; a measuring amplifier is introduced, the input of which is connected to the analog input of a voltmeter and the second input is a switch and the output through the key is with the integrator input, and the pulse number divider connected between the second output of the control logic unit and the digital counter input, the auxiliary output of which is connected to the second input of the control logic unit, the control inputs of the key and the switch are connected to the third and fourth output control logic logic.

FIG. 1 shows a block diagram of the device; in fig; 2 - time diagram, where the y-axis reflects the voltage measurement at the integrator output, and the abscissa axis - the time of its operation; in fig. 3 - dependence of the instrument reading on the measured voltage.

The analog input of the device is connected to the input of measuring amplifier 2 and the input of switch 3. The output of measuring amplifier 2 is connected via switch 4 to integrator 5, and the source 6 of the reference voltage is connected to the input of integrator 5 via switch 3. The output of integrator is connected to comparator 7, and the latter with control logic block 8, which has four outputs for controlling directly key 4, switch 3, pulse number divider 9 and digital counter 10.

Two inputs of block 8 logic uprayLinin respectively connected with the output of the digital counter 10 and the generator 11 high-frequency pulses. The output of the digital counter 10 is connected to the reading device 12.

The voltage measurement is carried out as follows.

The signal from the control logic unit 8 to the control input of the key 4 provides the connection of the output of the measuring amplifier 2 to the input of the integrator .5.

The voltage applied to the analog input of the device is amplified by amplifier 2 and integrated over a period of time t - t (see Fig. 2) by the integrator 5. The voltage at the output of the integrator is equal to

UbbUL.HMT. Ux К, K.j (Ч-Ц), (1) where and is the measured voltage applied to the analog input of 1 voltmeter;

K. — gain gain of amplifier 2; K - transfer coefficient integ-.

Rattor 5;

t. - the initial moment of voltage integration, equal to the value of and, K;

tj is the final moment of integration of this voltage. At time t, at the command of the control logic block, key 4 is opened; disconnection from the amplifier output of the amplifier occurs and at the same time through the switch 5 the source 6 of the reference voltage to the integrator's output. The voltage Uq of this source starts the discharge of the integrator.

At the moment t2, from the generator 11, high-frequency pulses are received by pulses through a divider 9 of the number of pulses into a digital counter 10.

The conversion factor of the divider is chosen equal to the reciprocal of the gain of the measuring amplifier 2. At the time t, j (Fig. 2)

The integrator discharge ends with a voltage UQ to zero and the signal of the comparator 7 zero level block 8 control logic prohibits the flow of high-frequency pulses into the digital counter 10. During the supply time for the input of the integrator voltage Uo, the voltage at the integrator output decreases to zero in co. . according to the ratio

EXIT IMT. () (2)

From ratios. (1) and (2) follows

(Vt,). (3)

 as the time intervals are proportional to the number of pulses and the difference is equivalent to a constant number of pulses, then (3) can be written as

OK

A (4)

and.

where n is the number of pulses counted by the counter 10 during the time interval. Taking into account the conversion factor of the divider, since K, we have n p. CDR or

UK Ig

(five)

As can be seen from (5), there is a linear relationship between the number of pulses nV. , counted by the meter during the integrator discharge, and the measured voltage 13c.

The measurement result is displayed on the reading device 12 in digital form.

In the event that the measured voltage has a sufficiently large value. A mask at which it is greater than the upper limit of measurement, the counter is 10 undefined.

The overload signal goes to control logic block 8, which, using key 4, disconnects the amplifier from the integrator and, acting on switch 3, connects the analog input of a 1 voltmeter to the input of the integrator 5. The instrument operates as described above. the only difference is that amplifier 2 does not participate in the work and divides fir 9.

FIG. Figure 3 shows the straight line passing through, points 0.1 and 2, which reflects the linear nature of the scale of the voltmeter. The line passing through points 3.1 and 2 reflects the character of the scale of known block diagrams of digital integrating voltmeters.

Linearization of the instrument scale is achieved due to the fact that the voltage in the path of the analog part of the instrument significantly exceeds the total value

Claims (1)

Claim A digital integrating voltmeter containing an integrator in series, a zero-level comparator and a control logic unit, a reference voltage source connected through the switch to an integrator input, a high-frequency pulse generator connected to the first input of the control logic unit, the first output of which is connected via a digital counter with a readout device, with the exception of the fact that, in order to increase the accuracy of voltage measurement, a measuring amplifier is introduced into it, the input of which is connected to the analogue input of the voltmeter and the second input of the switch, and the output through the key with the input of the integrator, 'and the divider of the number of pulses included between the second output of the control logic unit and the input of the digital counter, the additional output of which is connected to the second input of the control logic unit, and the control inputs of the key and the switches are connected respectively to the third and fourth outputs of the control logic block.