JPH05322943A - Frequency measuring apparatus - Google Patents

Abstract

PURPOSE:To measure the frequency of a signal to be measured by counting the pulses of a first reference frequency with a first counter during a period to be measured, which is obtained by dividing the frequency of the signal to be measured with a specified frequency dividing ratio, counting the reference periods with a second reference frequency, which is proportional to the frequency dividing ratio, outputting pulses at every counting of the first counted value, and counting the pulses. CONSTITUTION:A period control part 8 receives a signal to be measured having a frequency F through an input terminal and divides the frequency with a frequency dividing ratio M. A first counter 9 receives a period Ta obtained with the control part 8 and a first reference frequency signal Fa, obtains the counted value N=TaXFa and holds the value in a latch 10. A program frequency divider 11 counts the pulses of a second reference frequency signal Fb for a reference period Tb and outputs the pulses at every N counts during the period. A second counter 12 counts the pulses outputted from the frequency divider 11 and obtains the counted value C. The counted value C indicates the frequency F of the signal to be measured. The obtained frequency is displayed on a digital display device 13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a frequency measuring device mounted on a portable multi-digital meter or the like, and more particularly to a frequency measuring device for measuring a period of a signal under measurement and calculating the frequency. Is.

[0002]

2. Description of the Related Art A functional block of a conventional frequency measuring device is shown in FIG. In this device, a period counting unit 2 for counting a period T of a signal under measurement having a frequency F input to an input terminal 1 with a reference frequency pulse, the period T obtained here is F = 1.
The frequency conversion unit 3 for converting the frequency from / T and the frequency counting unit 4 for counting the frequency F of the signal under measurement as the number of pulses within the reference time are provided and the frequency F of the signal under measurement is 1K.
When the frequency is less than Hz, the signal obtained by the frequency conversion unit 3 is selected by the selector 5 and sent to the display circuit 6 to be displayed on the display device 7 such as an LCD. The signal obtained in step 1 is selected and similarly processed.

[0003]

As described above, in the prior art,
Since the measurement method for obtaining the frequency value was different depending on the magnitude of the frequency, the data processing after measurement and the processing for display became complicated. For example, when controlling with a microcomputer, the control program was large. There was a problem such as becoming.

The object of the present invention is to achieve high and low frequencies,
It is an object of the present invention to provide a frequency measuring device that prevents an increase in the number of program steps of a microcomputer that controls the entire device by measuring the frequency by measuring the period.

[0005]

For this reason, the frequency measuring device of the present invention includes a cycle control section for inputting a signal to be measured and dividing the cycle by a predetermined frequency division ratio to obtain a cycle to be measured. During a period to be measured, a first counter that counts pulses of a first reference frequency and a second reference frequency that is proportional to the division ratio are used to count the reference period, and a pulse is output for each count of the first count value. And a second counter for counting the output pulses of the program frequency divider. The frequency of the signal under measurement is obtained from the count value of the second counter.

[0006]

EXAMPLES Examples of the present invention will be described below. FIG. 1 is a block diagram of a frequency measuring device according to the embodiment. Reference numeral 8 denotes a cycle control unit for inputting a signal under measurement having a frequency F from an input terminal and dividing the frequency by a division ratio M. When the cycle of the ratio measurement signal is a predetermined length or less, the division ratio M is increased. The processing is performed so that the obtained cycle Ta falls within a predetermined range. Reference numeral 9 denotes a first counter, which inputs the period Ta and the reference frequency signal Fa obtained by the period control unit 8 and counts the number of pulses of the reference frequency signal Fa during the period Ta to obtain a count value N = Ta × Obtain Fa. Reference numeral 10 is a latch for temporarily holding the count output N of the first counter 9. 11
Is a program frequency divider, which counts the pulses of the reference frequency signal Fb during the reference period Tb, and outputs a pulse every N counts during that period. 12 is a second counter,
The pulses output from the program frequency divider 11 are counted and the count value C is obtained. When the second counter 12 overflows the first predetermined value, the frequency division ratio M of the cycle controller 8 is increased, and when the second predetermined value is not reached, the frequency division ratio M is decreased. This count value C indicates the frequency F of the signal under measurement. Reference numeral 13 is a digital display, which displays the obtained frequency.

The signal to be measured having the frequency F applied to the input terminal 1 is frequency-divided by the frequency division ratio M by the period controller 8 to obtain the period T by the following equation. Ta = M / F Here, if 1 / F = T, then Ta = M · T, and the cycle of the input signal is multiplied by M. First counter 9
The count value N obtained at is N = Fa · Ta, which is held by the latch 10. Therefore, in the program frequency divider 11, C = (Fb · Tb) / N 2 = (Fb · Tb) / (Fa · Ta) = (Fb · Tb) / [Fa / (M / F)] = F (Fb * Tb) / (Fa * M) is performed and this is counted by the counter 12. Here, the reference frequency Fb is associated with the frequency division ratio M of the cycle control unit 8 and a frequency obtained by multiplying another reference frequency Fc by M, that is, F
When b = M · Fc is set, C = F (M · Fc · Tb) / (Fa · M) = F [Tb (Fc / Fa)]. The value in [] is a fixed value, so the count value C
Is a value proportional to the frequency F of the signal under measurement. And
For example, Tb = 0.5s, Fc = 2MHz, Fa = 1M
If it is set to Hz, C = F, and the frequency of the signal under measurement can be obtained as it is.

[0008]

As described above, according to the present invention, since the frequency is constantly measured by measuring the cycle, the control becomes simple and the number of program steps can be reduced.

[Brief description of drawings]

FIG. 1 is a block diagram of a frequency measuring device according to an embodiment of the present invention.

FIG. 2 is a block diagram of a conventional frequency measuring device.

[Explanation of symbols]

8: cycle control unit, 9: first counter, 10: latch, 1
1: Program frequency divider, 12: Second counter, 13: Frequency display.

Claims (2)

[Claims] 1. A period control section for inputting a signal to be measured and dividing the period by a predetermined division ratio to obtain a period to be measured, and counting pulses of a first reference frequency during the period to be measured. A first counter, a program frequency divider that counts a reference period with a second reference frequency that is proportional to the frequency division ratio, and outputs a pulse for each count of the first count value, and an output of the program frequency divider. A frequency measuring device comprising a second counter that counts pulses, and obtains the frequency of the signal under measurement from the count value of the second counter. 2. The frequency measuring device according to claim 1, wherein the cycle control unit changes the frequency division ratio by overflow or downflow of the second counter.