SU1451862A1 - Two-cycle integration a-d converter - Google Patents

Abstract

The invention relates to a measurement technique and is intended to convert a voltage into a digital code. The invention makes it possible to increase the accuracy of the conversion. This is achieved in that the device containing the amplifier 1, the keys 3,4, the control unit 2, the integrator 5, the comparator 10, the pulse generator 8, the pulse counter 15, the integrator 9, the keys 11,12,13, the triggers 6,14 are entered , element 7, comparator 16. 2 ill.

Description

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The invention relates to a measuring technique, in particular to ana-digital converters, intended for converting a voltage into a digital code.

The aim of the invention is to increase the accuracy of the conversion.

FIG. 1 shows the time function of the analog-to-digital Q scheme of push-pull integration; in fig. 2 - time diagrams of his work.

The converter contains amplifier 1, control unit 2, keys 3, 4, integrator 5, trigger-6, element 7, pulse generator B, integrator 9, comparator 10, keys 11–13, trigger 14, pulse counter 15, comparator 16.

The analog-digital converter push-pull integration works as follows.

In the initial state, the keys 3j 4, 11, 12 are open, the key 13 is closed. 25 At the outputs of the integrators 5, 9, the voltage is 0. At the initial moment-time t, a signal is produced (Fig. 2a), a trip switch 3. The charge of the integrator 5 begins with the sum of the converted voltage and the bias voltage U ,. (Fig. 2c). Charging continues until time t, when key 3 opens. In this case, the trigger 6 is set to the state in which the key 4 is closed (Fig. 26). In addition, the signal from the trigger 6, having passed the element 7, closes the key 11, the filling of the counter 15 begins. pulse frequency f. , coming from the first output of the generator 8 Prti de integrator 5 to the level Uji, (fig. - 2c) at time tq triggers the comparator 10 (fig. 2d), while the trigger 14 overturns, the signal from its output through element 7 opens key 11. The charge of the integrator 9 begins with the output voltage of the integrator 5 (Fig. 2e) and the counter is filled with 15 pulses with a frequency of 0.5 f, the discharge continues until the moment t, when the output voltage of the integrator 9 decreases to O and works the comparator 16; With this, the trigger 14 is overturned, the key 13 is closed, and the key 12 is opened. The signal from the output of the trigger 14 returns the trigger 6 to the initial state. The conversion cycle ends. Rezulg

thirty

55

35

40

45

d -

1451862

The conversion code entered into the result counter is determined from the expression

t (t, - c) „-« - (tj-tj) | 2. (one)

Due to the linearity of the input voltage of the integrator 5 and given that the output voltage of the integrator 9

is.

and

out mnt 9

 j.

dt oh

t, you can write:

ts 4 4-3

chi (t.ts)

(2)

The filling of the counter 15 is made from the generator 8 through the keys 11 and 12. With the closed key 11, the filling frequency of the counter is equal to

closed key

1 - if 2

On the inter

shaft t, - t, the key 1 1 is closed, in the interval tj.- tj is the key 12. As a result, N pulses go to the input of the counter 15, and

N „(t

 t h +) b. -i 2.

or taking into account (2) N "(C- t,)

where k is a conversion factor equal to

 k (and m)

 f.

J-.b f-f

 -O and

ETSIL

Values and conditions

cm f

and and

Cwi

are chosen

 EI

icj °

one

U value

cm,

dt i and

CMj

./c is taken into account by pre-recording the corresponding code result in the counter.

Due to the double integration of the reference voltage on the interval

tstj increases the accuracy of

Zni of the interval duration tg .. The accuracy is increased due to the fact that the duration of the second cycle is not determined by the instantaneous value of the output voltage

Claims (1)

Claim A push-pull integration analog-to-digital converter containing an amplifier, the first input of which is an input bus, and the output is connected to the information input of the first key, the output of which is combined with the output of the second key and connected through the first integrator to the first input of the first comparator, the information input of the second key is a bus the source of the reference voltage, the control input of the first key is connected to the output of the control unit, a pulse counter, a pulse generator, characterized in that, in order to increase conversion, two triggers are introduced into it, the And element, the third, fourth and fifth keys, the second integrator and the second comparator, the first input to the integrator and the third key, the second input of the comparator is the bus of the first potential, and the output is connected to the installation input in О of the first a trigger, the input of which is connected to the output of the first comparator in 1, the direct output of the first trigger is connected to the control input of the fourth key and the first input of the And element, the inverse output is connected to the control input of the third key and the input of O in the second trigger, the installation input in G of which is connected to the output of the control unit, and the direct output is connected to the control input of the second key and the second input of the And element, the output of which is connected to the control input of the fifth key, the information input of which is connected to the first output of the pulse generator , the second output of which is connected to the information input of the fourth key, the output of which is combined with the output of the fifth key and connected to the counting input of the pulse counter, the first and second bias voltage buses are Accordingly, by the second inputs of the amplifier and the first comparator, the output of the first integrator is connected to the first input of the second integrator, the second input of which is connected to the information one and connected to the outputs by the input of the third key. second VNIIIPI Order 7091/55 Circulation 879 _____ Subscription Custom polygr. ave, city of Uzhhorod, st. Project, 4