SU866496A1 - Digital frequency meter of low and infralow frequencies - Google Patents

Description

The invention relates to a digital electrical measuring technique and can be used as a high-speed low and infra-low frequency meter.

Known devices containing triggers, a generator, counters, keys pj.

The disadvantage of these devices is the low accuracy of the measurement.

The closest in technical essence to the proposed one is a device containing a first key and a trigger connected in series, a second key connected in series, a code counter and converter, a reference frequency generator, a third key and a reversible counter G2] connected in series.

A disadvantage of the known device is low measurement accuracy.

The purpose of the invention is to increase the exact jq measurement.

This goal is achieved by the fact that in a digital frequency meter containing a first key and a trigger-ser ₍ a second key, a counter and a code converter connected in series, as well as a reference frequency generator connected in series. A third key and a reversible counter, a control unit and series connected a code converter of the input frequency into the time interval and an OR element, the output of which is connected to the first input of the second key, the second input of which is connected to the first input of the converter to ode of the input frequency but the time interval, the second input of the latter is connected to the second output of the counter, while the third input of the input code converter is connected to the output of the reverse counter, the second input of which is connected to the first output of the control unit, the second output of which is connected to the second input of the third key, the third output of the control unit is connected to the second output of the counter, the first input of the control unit is connected to the output of the code converter, the second input of the control unit is connected to the output of the trigger, and the fourth The th output of the control unit is connected to the input of the first key.

The drawing shows a structural diagram of the proposed device.

The device contains a key 1, trigger 2, element 3 OR key 4, counter 5, code converter 6, control unit 7, reference frequency generator 8, key 9, reversible counter 10, input frequency code converter 11 in a time interval.

The device operates as follows.

Initially, block 7 connects the input signal through key 1 to the input of trigger 2, which, in turn, through element 3 and key 4 opens the way to the output pulses of generator 8 and counter 5 over a time interval equal to the period T of the input signal. After that, block 7, by the signal of trigger 2, closes the output of key 1 and in counter 5, a code is obtained proportional to the period of the input signal (N _t ). Next, the converter 6 converts the counter code 5 inversely to the time interval for which the key 9 is opened using block 7 and the output pulses of the generator 8 are counted in the addition mode. After receiving the N code, the input frequency values with the errors of the converter 6, block 7 resets to the initial state counter 5 and allows the converter 11 to convert the code N into the time interval T _{4 f} for. which using key 3 and block 7 opens the key 4 and the output pulses of the generator 8 are counted in the counter 5. the code generated in counter 5 is again converted by the converter into the time interval for which the key 9 is opened and the pulses of the generator 8 are subtracted from the code recorded in the reverse counter 10. As a result, the difference Δ ₄ = Ν-Ν ₄ appears in counter 10.

Next, block 7 connects the input signal to the trigger 2 input, opens the key 4, and in the counter 5 the code _{получается ύ} .3τοτ code is converted by the converter 6 into a time interval, during which the pulses of the generator 8 are counted in counter 10. As a result, in the counter 10 it turns out the first corrected result of the input frequency Ν ^ Ν + Δ ^ ΙΝ-Ν.

Further, an iterative measuring and computing process, i.e. alternation

868496 the connection to the key input 2 of the time intervals of the input signal and the converter 11, as well as the operations of addition and subtraction, can be continued until the 5th and corrected result ^N cn ^{= N +} W- ^{+ A} n

The iterative process can be stopped by block 7 either on a specific number of correction cycles or upon receipt of Δ. £ ί), where Q is the quantization step.

It is easy to prove that under the equation. time intervals of the input signal and, 5 of the converter 11, the condition Δ-ΐ 6 I will be satisfied for which no more than 2-3 correction cycles will be required, since the errors of the converter 6 usually do not exceed several percent.

₂₀ As can be seen from formula (1), the corrected measurement results will always have higher accuracy, which can significantly reduce the accuracy requirements of the transducer 6,

2 _{5 of the} only complex unit of the device, Thus, the converter 6 is significantly simplified compared to those available in the known device. It should also be noted that the proposed _eo device is not critical to slow changes in the output frequency of the generator 8, and therefore, the generator 8 can be implemented in the form of conventional RC or L C generators, which also allows to simplify the device (in the known case, a crystal oscillator of ³⁵ torr is needed).

The proposed device allows approximately an order of magnitude or more to increase the accuracy of measurement. In the tracking mode, the measurement time ⁴⁰ can also be reduced.

Claims (2)

1. Kyrianak N, V. and Dudykevich V. B. Methods and devices of ai (measuring the low and infra-low frequencies. Lviv, Vishcha Shkscha, 1975. 2. Avtometri, 1969, No. 2, p. 39-45.