CS214037B1 - Circuit for determination of the starting time of analog-to-digital converter in digital measuring apparatus with two-cycle integrating method - Google Patents

Description

(54) Circuit for determining the start time of the A / D converter in a digital measuring instrument with two-stroke integration method

The invention dilutes a circuit for determining the start time of an A / D converter in a digital meter with a two-stroke integration method so that an analogue digital converter counter can be used to determine the start time needed to stabilize the meter input. ⁵

For one-time start of digital measuring device conversion (eg for stand-alone use or in measuring devices) it is necessary to ensure minimum time interval between connection of measured value (eg voltage, current, resistance etc.) and analogue-digital conversion start necessary for stabilization of input circuits . The length of the time interval is different for different measured quantities and ranges.

When using monostable flip-flops, the time interval can be defined with low accuracy (♦ tens of percent), for more accurate determination monostable flip-flops must be specially adjusted and temperature compensated. The end of the time interval is not phased on waveforms that take place in the analog-to-digital converter of the instrument. The use of monostable flip-flops complicates the manufacturing and service diagnostics of the device and its parts. The possibility of undesirable starting of monostable flip-flops must also be taken into account in larger instrument constructions.

All the disadvantages described are eliminated by the proposed circuit according to the invention, which is based on the fact that the control circuits of the analog-to-digital converter are connected to the terminal and their output is connected to one input of the zero counter circuits having

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The output is connected to the reset counter of the main counter, the output of this counter is connected to the input of the counter state evaluation circuit and the output is the counter state evaluation circuit connected to the first input of the counter zero circuit and the second input of the analog digital converter control circuits. the first input of the counter preselection circuits, the second input of which is connected to the output of the range decoder, the output of the counter preselection circuits is routed to the preset input of the main counter, the first input of this main counter is connected to the output connected to the third output of the analog-to-digital converter control circuits.

Fig. Is a block diagram of a circuit for measuring the start time of an analog-to-digital converter in a digital measuring instrument with a two-stroke integration method. To terminal 1, the analog-to-digital converter control circuits 40 are connected by their first input 41 ,. The analog-to-digital converter control circuits are further provided with a first output 43 for connection to counter reset circuits 50, a second output 44 for connection to counter preset circuits 80, and a third output 45 connected to the counter input twist circuits 20 which are connected to the first input 31 of the analog-to-digital converter main counter 30, which is further provided with a reset input 32 to connect the counter-reset circuits 50 via its output 53. Further, the analog-to-digital converter main counter 30 has a preset input 33 and output 34 for connection . The range decoder 70 is outputted to the second input 82 of the counter preset circuits 80, these circuits further having a first input 81 and an output 83 for connection to the preset input 33 of the main counter 30 of the analog-to-digital converter.

After converting the start pulse to terminal 1, the analogue-to-digital converter control circuits 40 are also sent one pulse to the first output 43, second output 44 and third output 45. which in the following time sequence will reset, preselect, count the main counter 30 . Resetting is performed by the counter reset circuits 50 through the counter reset input 32. Presetting is provided by counter preselection circuits 80 based on the state of the range decoder circuits 70 through preset input 33 of main counter 30.

The pulse from the third output 45 via the second input 22 releases the output 23 of the parallel input circuitry 20 and the counter counts forward pulses given by the frequency of the oscillator 10 from the default state determined by the preselection. The preset state is selected so that the state of only one decade of the main counter 30 can be evaluated, and the highest one, with a pulse in the counter state evaluation circuits 60 deriving from the change of only one of the weights (the state remains unchanged). the first input 51 of the counter reset circuits 50 will reset it, and the second input 42 in the analog-to-digital converter control circuits 40 terminates the stabilization time interval and initiates the next clock of the digital meter. At the same time, through the second input 22 from the third output 45 of the control circuits 40 of the analog-to-digital converter, the output 23 of the first input circuits of the counter 31 is barred.

It is obvious from the description of the connection that it is possible to precisely determine the moment of entering the start of the transmission according to the method of using the digital measuring instrument. The invention can be used in digital multimeters.

Claims (1)

SUBJECT OF THE INVENTION A circuit for determining the start time of an analog-to-digital converter in a digital measuring instrument with a two-stroke integration method, characterized in that it is connected to terminal (1) (first input (41) controlling the analog-to-digital converter circuits (40). with a second input (52) of the counter reset circuits (50) having an output (53) connected to the reset input (32) of the main counter (30), the counter output (34) of which is connected to the input (01) of the circuits (60) the counter evaluation state and the output (62), the counter state evaluation circuit (60) is connected to the first input (51) of the counter reset circuits (50) and the second input (42) of the analog-to-digital converter control circuits (40). are connected to a first input (81) of the counter preset circuits (80), the second input (82) of which is connected to the output (71) of the range decoder (70), while the output (83) of the circuit The counter preset (80) is routed to the preset input (33) of the main counter (30), the first input (31) of said main counter (30) being connected to the output (23) of the bradlovaeleh circuits of the counter input (20) and 22) the counter input gate gating circuits (20) to a third output (45) of the analog-to-digital converter control circuits (40).