SU970255A1 - Digital frequency meter - Google Patents

Description

(54) DIGITAL FREQUENCY

The invention relates to measurement technology and can be used in automatic frequency meters.

A digital frequency meter with automatic selection of measurement limits is known, containing an input pulse shaper, a time selector, a decisive pulse counter, a forming trigger, a control trigger, a decoder of state 1 of the last and 9 penultimate counters of the counter, a trigger for storing 1 most significant bit of the counter, a shaping unit yes increasing in time model intervals of time formed by a shift register, a line of ten-day pulse frequency dividers, a circuit of impulse-potential cells The user, the AND scheme and the OR scheme, the trigger trigger, the generator of the smallest sample time interval TC, and the information output device 1.

A disadvantage of the known device is low measurement accuracy.

Of the known devices, the closest in technical essence to the present invention is a digital frequency meter, a salt generator connected in series to an input driver, a key, a pulse counter and a digital recording unit, as well as a valve block consisting of a set of elements And whose first inputs are connected to the corresponding outputs. the pulse counter and the first element OR, the inputs of which are connected to the outputs of the elements AND, the second element OR and 10, therefore connected the generator of the exemplary frequency, the control unit , A frequency divider, the decoder and the counter number of periods f2.

The disadvantage of the known device

15 is a low measurement accuracy.

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

The goal is achieved by the fact that a digital frequency meter containing 20 serially connected input driver, key, pulse counter and digital recording unit, as well as a valve block consisting of AND elements, the first inputs

25 of which are connected to the corresponding outputs of the pulse counter and the first element OR, the inputs of which are connected to the outputs of the elements AND, the second element OR and the series-connected generator of exemplary frequency, | an adjustment unit, a frequency divider, a series-connected source of an enabling signal and a switch, the outputs of which are connected to the second inputs of the elements AND block of the valves, as well as the first and second drivers and an incomplete cascade, are inserted, the first inputs of the first and second drivers are interconnected , the output of the second element OR is connected to the first input of the mismatch cascade, the second input of which is connected to the output of the first shaper, the second input of the second shaper is connected to the output of the wrong fault The output of the first element OR is connected to the second input of the first driver, the output of the second driver is connected to the second input of the key, the outputs of the frequency divider are connected to the inputs of the second OR element, and the second input of the adjustment unit is connected to the first inputs of the driver and the synchronization pulse bus . Figure 1 shows the structural scheme of the proposed frequency meter; on . figure 2 - timing diagrams illustrating the operation of the frequency counter. The device contains an input driver 1, a key 2, a pulse counter 3, a digital registration unit 4, a valve unit 5 containing element Ib, and a first element OR 7 "The device also contains an OR element 8, connected in series generator 9 of exemplary frequency, adjustment unit 10 and a frequency divider 11, an enable signal source 12, a switch 13. Formers 14–15, a mismatch cascade 16, forming a time interval generator 17. The operation of the device is as follows. Before starting measurements, the switch 13 is used to set the permissible measurement error. This is achieved by applying the permitting potential to the second input of one of the elements 6 (for example, the 1st element 6). The oscillator U is fed to the input of the shaper 1 (Fig. 2), the output of which is a sequence of pulses and 2 following the measurement period Frequency of impulses will pass on the output of the key 2 only if the second input of the key 2 contains the resolving potential generated by the shaping 15. When the ultrasonic synchronization pulse appears, the ultrasonic imagers 14 and 15, which can Triggers will be used, set to one, the output of shaper 15 is set to a single level signal that permits key 2. As a result, the pulses from shaper 1 output through key 2 to the input of counter 3 pulses. the former 14 also sets a single level signal supplied to the second input of the cascade 16. This signal is a prohibitive signal for the cascade 16 and, if present, the signal supplied to the first input of the cascade 16 cannot pass to its output. Therefore, until the driver 14 changes its state under the pulse from element OR 7, the pulses from the output of element OR 8 do not pass through cascade 16 to the second input of driver 15 and do not change its state:,. From the moment of the formation of the pulse Ug in the imaging unit 15, the counter 3 counts the pulses arriving at its input. When the number of 3 pulses counted by the counter becomes such that the output of the 1st decade of the counter 3 has a pulse Ug, then this pulse will pass to the output of the 1st one. element 6, since it is at its second input that there is a resolving potential from switch 13. Through element 7, this pulse will pass to the second input of shaper 14 and set it to the zero state. As a result, the formation of a pulse Ug will be completed, which determines the minimum period of time during which the frequency measurement of the input signal is made with an error not exceeding the allowable one. Moreover, the moment of termination of this pulse Ur coincides with the moment of appearance of the pulse Ug. However, this time interval is not exemplary, since the end of the exemplary time interval is determined by one of the pulses from the output of divider 11. After the formation of the pulse Ug. under the influence of zero potential from the output of the shaper 14, the mismatch cascade 16 is prepared by the second input to pass pulses from the output of the OR element to its output. at the output of the cascade 16 and, arriving at the second input of the driver 15, sets it to the zero state. Thus, at the output of the imaging unit 15, the formation of a pulse Ug, determining the sample time interval, will be completed. After completing the formation of this pulse

The resolving potential at the second output of switch 2 is terminated; therefore, the passage of pulses of the measured frequency to the input of counter 3 stops. Consequently, the contents of counter 3 will characterize the value of the measured frequency measured with an error not exceeding the specified one.

The proposed digital frequency meter allows to measure the frequency of the input oscillations with an error not exceeding the specified frequency over a wide range of variation of the measured frequency. This is achieved by the fact that in the proposed digital frequency meter, when the value of the measured frequency y changes, the sample time interval Td automatically changes during which the number of periods of the measured frequency is calculated. B. The result of this measurement error, determined from the expression

will be maintained at a given level and will not exceed the allowable value, i.e. when using this device, the accuracy of frequency measurement is improved.

In addition, since measurements with a given accuracy are achieved. Due to the automatic setting of the minimum possible duration (optimum value) of the model time interval T, during which the pulse counter counts the number of periods of the measured frequency fy, then per unit time using the proposed frequency meter make more measurements (counting cycles) than is possible with the manual (non-optimal) setting of the TC value in the prototype. This leads to an increase in speed.

Claims (2)

1. Author's certificate of the USSR 474760, class. 01 R 23/10, 1975.. 2. USSR author's certificate 370537, class C 01 R 23/10, 1973 ..