SU523527A1 - Correction Device Zero Analog Digital Converter - Google Patents

Description

one

This invention relates to analog-to-digital converters used in electrical engineering.

A device for zero-time correction of a single-pulse time pulse puller is known, in which the zero correction is performed by the automatic measurement of the level at the inputs of the amplifier or comparators by the value of the drift voltage 1. However, this device has a complex structure.

It is also known a zero correction device containing three keys, the input of the first key being connected to the input signal bus, the input of the second key having a common thickness, and the outputs of the first and second keys are connected via a DC amplifier to the first input of the first commersator, the second input of which is connected to the first input of the second comparator and the output of the generator of linearly varying voltage, and the output with the first input of the circuit "And, the second input of which is connected to the output of the second comparator, the third input to the output of the pulse generator, and the output to the counter, the output of the third key is connected to the second input of the second comparator and to one capacitor plate, the second plate of which is connected to the common ground

2

Such a device also has a complex structure.

The purpose of the invention is to simplify the device. This is achieved by introducing into the proposed device a controlled current source, the first input of which is connected to the output of the first comparator, the second input to the output of the second comparator, and the output connected to the input of the third key.

The drawing shows a structural electrical circuit of the proposed device.

The device contains keys 1, 2, DC amplifier 3, first comparator 4, second comparator 5, linear variable voltage generator 6, key 7, capacitor 8, controlled current source 9, circuit

"And 10, the pulse generator And, the pulse counter 12, and the input of the key 1 is connected to the input signal bus, the input of the key 2 is connected to the common length, and the outputs of the keys 1 and 2 are connected via the DC amplifier 3 to the first

the input of the first comparator 4, the second input of which is connected to the first input of the second comparator 5 and the generator output of the linearly varying voltage 6, and the output to the first input of the circuit “And 10, the second input of which is connected to the output of the second KOiMnapator 5, the third input - To the output of the pulse generator I, and the output to the output of the pulse counter 12, the output of the switch 7 is connected to the second input of the second comparator 5 and one plate of the capacitor 8, the second cover of which is connected to the receiver, the first input of the current source 9 is connected to the output of the first sharatora th to 4, the second input - with the output of the second KOMioaparopa 5, and an output connected to the input key 7. The device operates in two ta-CTA. During the first cycle, the voltage of the total drift zero of the DC amplifier 3 and the comparators 4, 5 is determined and stored on the capacitor 8 connected to the second input of the comparator 5. During the first clock cycle, the key 1 is open and the keys 2 and 7 are closed. During the second one, key 1 is closed, the rest are open. The input voltage of the direct current current, 3, receives the test voltage bx, and its conversion takes place.

Automatic zero correction is performed as follows.

When the sawtooth voltage pulses are received from the source of the linearly varying voltage 6, the comparators 4 and 5 are triggered. The input of the DC amplifier 3 is connected to the common bus through the key 2. In this case, the conversion result is determined by the length of the JX H-interval. the time between triggers of comparators 4, 5, is equal to the total drift of zero DC amplifier 3 and comparators 4, 5. To correct the drift zero, it is necessary to achieve such a state of circuit when the comparators 4, 5 occur in time To do this, the signals from com.aparators 4, 5 control current source 9 generates current pulses, the duration of which is equal to the duration of the time interval between the operation of the comparators 4, 5, and the current direction is determined by the order of operation of the comparators, i.e. the drift polarity . The current pulses from the controlled current source 9 through the switch 7 recharge the capacitor 8, measure the level of operation of the comparator 5. The direction of overcharging of the capacitor 8 is chosen so that the difference between the thresholds of operation of the comparators 4, 5 decreases and, consequently, the length of the time interval between operations mi comparators 4, 5 also decreased. The steepness of the voltage rise on the capacitor 8 when it is recharged should not be greater than the steepness of the sawtooth voltage from the generator of the linearly varying voltage 6. Under these conditions, the duration of the time interval between the operations of the comparator O: 4, 5 for one or several ticks of poooorazny voltage becomes almost zero, i.e., the entire device is corrected. After zero correction, a working and conversion is performed. Key 1 closes and keys 2 and 7 open. The voltage to be converted is fed to the input of the DC amplifier 3. The duration of the time interval, proportional to AND, is measured by counting the pulses from the pulse generator AND by the pulse counter 12. The AND 10 circuit will play the role of a pulse selector. The frequency of zero correction is determined by the range of changes in the external conditions and the quality of the applied 1B elements.

Thus, the proposed device makes it possible to efficiently make automatic adjustment of the zero of the DC amplifier and the ADC comparators with a significantly smaller amount of the device circuit.

For. M l l a and 3 o b e t e u u

5 A zero-to-analog converter device containing three keys, with the input of the first switch connected to the input signal bus, the input of the second switch with a common bus, and the outputs of the first and second switches

0 is connected via a DC amplifier to the first input of the first comparator, the second input of which is connected to the first input of the second comparator and the output of the linear-varying generator: eNII, and the output -

5 with the first input of the circuit “And, the second input of which is connected to the output of the second comparator, the third input to the output of the pulse generator, and the output to the input of the counter, the output of the third key is connected to the second input

0 of the second comparator and to one capacitor plate, the second plate of which is connected to a common bus, characterized in that, in order to simplify the device, a controllable current source is additionally introduced into it, the first input of which is connected to the output of the first comparator, the second input output of the second comparator, and the output is connected to the input of the third key. Sources of information taken into account in the examination.

1.B. I. Shvetsky. Electronic measuring instruments with digital readout, Kiev, “TexHffia, 1970, pp. 33-36.

2..Radio and Electronic Engineering, No. 2, V. 40, 1970 (prototype).

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