SU991324A1 - Device for measuring signal frequency - Google Patents

Description

The invention relates to a measurement technique and can be used to measure the frequency of electrical oscillations. five

A device for measuring the frequency of signals consisting of a series-connected reference oscillator, a frequency divider, a trigger, a coarse counter, a divider with a variable division factor (DDC), a key, and an exact counter is known, and the trigger output is connected to a second input key, the output of the reference generator - with IBTOpiiM. DCDD input, and the device input; VA - q second inputs of coarse and accurate counters 13.

A disadvantage of the known device is low measurement accuracy .20

The closest in its technical essence to the invention is a device comprising a sequentially connected reference oscillator, a control unit and a key, the second input 25 of which is the input of the device, the first counter and a digital display panel connected in series, the pulse driver, the integrator and the analog connected in series -digital converter {.2,

A disadvantage of the known device is the measurement accuracy.

The purpose of the invention is to improve the measurement accuracy.

This goal is achieved in that a device for measuring the frequency of signals, comprising a series-connected reference oscillator, a control unit and a key, the second input of which is the device input, the first counter and digital display panel connected in series, the pulse generator connected in series, the integrator and analog-to-digital the converter, the shaper of additional pulses are introduced, the controllable delay line, the accumulator accumulating and the additional switch connected in series are connected, the second counter A digital-to-analog converter, the output of which is connected to the second input of the analog-digital converter, the output of the latter is connected to the first input of the accumulating adder, the second input of the latter is connected to the second input of the integrator and to the first output of the control unit, the second output of which is connected to the control input of the auxiliary key whose information input is connected to

the second input of the controlled delay line and the input of the device, the output of the key is connected to the first input of the shaper of additional pulses, the second input of which is connected to the first output of the accumulating adder; the second output of the latter is connected to the second input of the digital display, while the second input of the controlled delay line is connected to the control input of the key and the first input of the pulse generator, the second input of which is connected to the output of the controllable delay line, and the output of the driver of additional pulses is connected to the input row of the first counter.

Figure 1 shows a block diagram of a device for measuring the frequency of signals; 2 shows timing diagrams for the operation of the device.

The device contains a reference generator 1, a control block 2, a key 3, a shaper 4 additional pulses, a counter 5, a digital scoreboard b) Pt 7, a controllable delay line 8 (CRL), a shaper 9 pulses,

integrator 10, analog-to-digital converter 11 (ADC), accumulating adder 12, counter 13, digital-to-digital converter 14 (DAC).

. Figure 2 presents: a-pulses of the measured frequency f b. B, t -signals at the outputs of the control unit 2 - the first, second and third, respectively, - E - signal at the output. CCA 14; e, the signals at the outputs of the imaging unit 9 pulses and the integrator 10.; The device operates as follows.

Before starting the measurement, the counter 5, the counter 13 and the integrator 10 are in the zero state, and in the accumulator, the adder 12 is recorded 1.

The frequency is measured roughly as in conventional frequency meters, by counting the pulses N1 transmitted to counter 5 through the first key 3 during the measuring interval T1. This interval is formed at the first output of the control unit 2 from the signal of the reference generator 1 (Fig. 26).

At the same time, a signal is generated at the second output of the control unit 2. auxiliary measuring interval T2, opening key 7. It is fortified similarly to the main measuring interval (for example, dividing the reference frequency by a specified number of times and extracting a pulse of a certain polarity). In this case, the control circuit ensures that the condition is met (Fig. 2b). At the end of T2 century. counter 13 records the number N2, also characterizing the frequency f ,,. The value of the analog parameter at the output of the DAC 14 is inversely proportional to f, which will ensure the normalization of the conversion result in the A / D converter 11 relative to the period of the measured frequency.

In addition, the signal of the measured frequency fx through the ULL 8 arrives at the shaper 9. On the fronts of the measuring interval T1, the ULZ V delays the input signal by one period f. The imaging unit 9 generates pulses starting at the edges of the measuring interval T1 and ending with the arrival of the second pulse f (Fig. 2e). The duration of each of these two pulses, t and tg, depends on the phase relations of the reference and measured frequency, but their difference depends only on the measured frequency (up to) ULZ 8 can be made in the form of two D-flip-flops connected in series The input D of the first one is connected to the first output of the control unit 2, both synchronous inputs are connected to the input of the device, and the output of the second trigger to the input of the driver 9, the role of which in this case can be performed by the ORDER circuit.

From the output of the imaging unit 9. Pulses, the pulses t and t are fed to the integrator 10, which determines the area of each of them (Fig. 2g) and then to the A / D converter 11, which normalizes relative to T and digitizes the result.

Before the measurement is started, adder 12 is recorded 1. After measurement t, the number from the output of ADC 11 is subtracted from 1 recorded in accumulator adder 12, and then, after measuring tg, the number tg / Tp is added to the result. These operations accumulator 12 performs the signals from the third output of the control unit 2 (Fig.2), which also reset the integrator 10 (Fig.).

Thus, at the time of the end of the measurement, the number p 1 + dT / T is recorded in accumulative adder 12; rego, 23. The fractional part of this number enters the digital scoreboard 6 (at its lowest bits, and it is intact at shaper 4, which is a device that passes all pulses from the first input to the output and produces one pulse when it appears at the second input. It can be made in the form of a pulse shaper from a differential connected to the input of the OR circuit. If, then shaper 4 generates one pulse, increasing the number recorded in the first counter 5 to N + 1. If, then shaper 4 does not generate a pulse. In case of a higher error, digital code 6 is supplied with the code of the one recorded in counter 5, which is less by one. Improving the accuracy of measurement in comparison with the known device is explained next.

Since the t Ht pulses generated in the former 9 by the ULZ 8 have a duration of (1 - /) Tx and, therefore, repeating with high accuracy, the fronts, when determined by their integration with further digitization, are eliminated an error caused by the final speed of the former 9, used to determine the normalization value TX in series. The connected key 7, the counter 13 and the DAC 14 allows to determine T with high accuracy and to keep the result unchanged during the whole measurement process, f which is important for normalizing t and tg with the same coefficient NM. The use of the accumulator 1 of its adder 12 for determining the RT allows one to record the measurement result of t and t-2 immediately. after finishing them. measurement, thereby eliminating the error / arising in the known device as a result of the integrator itself and the drift of the subtraction device.

The use of new pulse generator elements, a second key, a second counter, a DAC, a controlled delay line, an accumulator, and connections favorably distinguishes the proposed device from the known one, since it allows to increase the frequency measurement accuracy at small measurement intervals.

Claims (2)

1. Ermolov R.S. Digital frequency meters. L., Energie, 1973. 45, 2. USSR author's certificate 482692, cl. G 01 R 23/02, 11.05.73. but T1 f g T2 g f1. nv well