SU408231A1 - DIGITAL LOW FREQUENCY METER - Google Patents

Description

one

The invention with respect to electrical measuring technology can be used to eliminate the methodological logic and extend the range of frequencies measured by digital low frequency meters.

The well-known digital low-frequency meter, containing a pulse shaper, summing and subtracting counters, comparing the device and a generator of exemplary frequency, is characterized by the presence of methodological accuracy and a narrowed range of measured frequencies.

The proposed meter is equipped with a multiplier of two sequences AND | Mulses, a valve and a discrete filter, the output of which is connected to the input of the subtractive counter and the pulse input of the valve, the potential input of which is connected to the output of the subtractive counter, the output is connected to the second input of the multiplier, the first input of which is connected the output of the key and the first input of the discrete filter, the second input of which is connected to the output of the multiplier. Such an embodiment of the device allows eliminating methodological errors and expanding the range of measured frequencies.

The drawing shows a block diagram of the proposed device.

The meter consists of a pulse driver 1, a summing counter 2, a comparing device 3, a valve 4, a generator 5 of an exemplary frequency, a switch b, a multiplier 7 of two pulse sequences, a discrete filter 8 and a subtracting counter 9.

The meter works as follows.

In the initial state, valve 4 and key 6 are closed, summing counter 2 and multiplier 7 are set to zero, discrete filter 8 is prepared for high frequency pulses output from key 6, and a constant number NO equal to twice the period code T is set at subtracting counter 9 upper frequency range;

N, 2Г f ,.

The measurement starts with the arrival of pulses of frequency fx from shaper 1 to the input of summing counter 2, whose capacitance is equal to N. In this case, key 6 opens for measuring time NTj and allows NTT pulses of the reference frequency to the first input of discrete filter 8. By passing

 about pulses through a discrete filter 8

the potential from the subtracting counter 9 opens the valve 4 and the multiplier 7 receives pulses from the outputs of the key 6 and valve 4. The pulses from the output of the multiplier 7 are fed to the second input of the discrete filter 8 and each short circuit prohibits the passage of one pulse from the first input of the filter 8 to its output . Thus, after unlocking the valve 4 and the first inputs of the discrete filter 8 and multiplier 7, the number of pulses is received: NT, h - and the second inputs are respectively the number of pulses NZ and Ng, which are associated with the number of Ni by the following ratios: N, 2N, N, / N, where 2INo is the multiplier transfer coefficient 7. By the end of the measurement, in the subtractive counter 9 the number / V / remains, which is proportional to the measured frequency: -. -.- t --.- Jr The meter allows direct reading frequencies in the range of / max AO / min - - iMSKcl oIf the measured frequency above the limit frequency, by the time at the end of the measurement (lock key 6); Beitil 4 will not be opened and a signal may be generated that it is necessary to switch to a higher frequency range. The transition to a lower range of, the measurement is made, as usual, with a small output code. Subject of the Invention A digital low-frequency meter containing a pulse shaper, summing and subtracting counters, a comparing device and an exemplary frequency generator, characterized in that, in order to eliminate methodical error and spread of the measured frequencies, it is equipped with a multiplier of two pulse sequences, a gate and a discrete the filter, the output of which is connected to the input of the deducting counter and the pulse input of the valve, the potential input of which is connected to the output of the deducting counter and the output is connected to the second input of the multiplier, the first input of which is associated with the output of the key and the first input of the discrete filter, the second input of which is connected to the output of the multiplier.