SU932418A1 - Device for measuring frequency - Google Patents

Description

I

The invention relates to a measurement technique, in particular, to devices for measuring frequency. . A known 4acTotbi to voltage converter containing a trigger, an integrator with a comparator, which form a delay circuit, a low-pass filter, a C11 dc amplifier. device operation.

The closest in technical essence to the present invention is a device for frequency measurement, comprising a series-connected delay circuit, a trigger, output signal drivers, a low-pass filter and a measuring device, as well as a switch, the output is connected to the control circuit. .

A disadvantage of the known device is the relatively low sensitivity to frequency change.

The purpose of the invention is to increase the sensitivity.

four

The goal is achieved by the fact that the device for measuring the frequency, which contains the first trigger, whose inputs through the controlled line are connected to the device, and the outputs of the first trigger through the drivers and filter are connected to the indicator, the switch, the output of which is connected to the control input of the delay line, the delay line and the second trigger, the output of which is connected to the input of the switch, and the inputs of the second trigger directly and through the delay line

20 are connected to the input of the device.

Claims (2)

FIG. 1 shows a block diagram of the proposed device; in FIG. 2 - time diagrams. 33 A device for measuring frequency contains a controllable delay line 1, a first trigger 2, output drivers, a low-pass filter, a measuring device 5, a switch 6, a delay line 7, a second trigger 8. Lines 1 and 7 of the back surface can be implemented, for example as delay lines, as a release circuit (GPN, one-shot) or as a device based on a given module. To control the delay value of line 1, you can change the length of the delay line, the threshold voltage, as well as the initial state of the counter or the frequency of the reference generator, depending on the method of implementing the delay line 1. Line 7 delay has a constant delay time. The delay line 7 and the second trigger 8 form a parallel channel for converting the input frequency with this delay time T. In FIG. 2 plots a, 6 represent the signals at the output of the trigger 8, and plots в, 1- at the output of the trigger 2 at different frequencies. The device works as follows. The input signal is fed to one input of the trigger 8 directly, and to the other through the delay line 7, which gives the delay TT. Thus, at the output of the trigger 8, pulses are generated, the duration of which ty is determined by the expression tj -r - T, where fy is the measured frequency (Fig. 2a) This signal goes to switch 6, where the value t is remembered until the next measurement cycle. In the next measurement cycle, the switch 6 sets the delay value T of the delay line 1 according to the expression Tj T − j, −nt ,. If the measured frequency does not change, pulses of duration (P41) are set at the output of trigger 2. n 1,2,3 (fig. 2c). Suppose, for example, that the frequency has gone down. The duration of the pulses at the output of the trigger 8 will be equal to - Ti (Fig. 26). X tniD In the next measurement cycle, the switch sets the delay T of the delay line 7 equal to (n + O- (; Xminf) (min And the pulse duration at the output of flip-flop 2 increases to (n H) (b. T) Txmin. Signal from the output trigger 2 through output drivers 3 is fed to a low-pass filter, which extracts the average voltage value. The voltage at the output of filter 4 is E4nM. (f) - t; t4nM) ((). where E is the output pulse amplitude output drivers: sensitivity of the proposed device S -E (n 1) .Tj. Technical and economic effect The invention is to increase the sensitivity of the transducer when measuring a frequency varying in a narrow range. Formula of frequency measurement device comprising a first trigger, whose inputs are through a controlled delay line and directly connected to the input of the device, and the outputs of the first trigger through drivers and a filter are connected and with an indicator, the switch, the output of which is connected to the control input of the delay line, whether or not 11 | e is that, in order to increase the sensitivity, have neither the delay and the second trigger, the output of which is connected to the input of the switch, and the inputs of the second trigger directly and through the delay line are connected to the input of the device. Sources of information taken into account in the examination 1. Instruments and experimental techniques, 1977, W 2, p. 101. 2. USSR Author's Certificate No. it10325, cl. G 01 R 23/00, 1972.