JPH0530772U - Frequency signal measuring device - Google Patents

Abstract

(57) [Summary] (Modified) [Purpose] To reduce the load on the microprocessor and enable accurate frequency measurement over a wide range from low frequency signals to high frequency signals. [Constitution] An event counter 3 to which a frequency signal to be measured is applied, a timer counter 2 having a latch function, a counter value from the event counter 3 and a timer counter 2
Microprocessor 1 that reads the count value of
The microprocessor 1 includes a counter value (No) from the event counter 3 read last time, a count value (Mo) of the timer counter 2 and a counter value (N1) read from the event counter 3 read this time. , The count value (M1) of the timer counter 2 is used to perform a predetermined calculation to obtain the frequency (Fi) of the signal to be measured.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an apparatus for measuring the frequency of a pulse frequency signal from a flow meter or a speedometer that outputs a pulse signal, and more specifically to a device for measuring the pulse frequency using a microprocessor. In addition, the present invention relates to a frequency signal measuring device that reduces the burden on the microprocessor and can measure the frequency with high accuracy.

[0002]

[Prior Art]

 4 and 5 are conceptual configuration diagrams of a conventional frequency signal measuring apparatus using a microprocessor. The one shown in FIG. 4 is composed of a microprocessor 1 and a timer counter 2 connected to the microprocessor 1. The microprocessor 1 inputs an input pulse (frequency signal) to be measured, and detects the edge of the pulse. The value of the timer counter 2 is latched each time it is detected. Then, after detecting the edge of the pulse, the value of the timer counter 2 is read in the interrupt process, and the difference from the previous value is calculated. This difference is the value measured as the pulse period. The one shown in FIG. 5 comprises a microprocessor 1 and an event counter 3 connected thereto, and a pulse frequency signal Sf to be measured is applied to the event counter 3. The microprocessor 1 reads the count value Ns of the event counter 3 at an interrupt of a fixed cycle Ts and calculates (count value Ns / fixed cycle Ts) to obtain the measured pulse frequency.

[0003]

[Problems to be solved by the device]

 The apparatus shown in FIG. 4 is suitable for measuring low-frequency signals, but there is a problem in that the number of interrupts to the microprocessor 1 increases as the frequency increases, and the load on the microprocessor becomes heavy. On the contrary, the apparatus of FIG. 5 is suitable for measuring a high frequency signal, but the measurement of a low frequency signal has a problem that the measurement time becomes long. The present invention has been made in view of these points, and an object thereof is to provide a frequency signal measuring device capable of performing highly accurate frequency measurement in a wide range from low frequency signals to high frequency signals. To do.

[0004]

[Means for Solving the Problems]

 The present invention which achieves such an object includes an event counter to which a frequency signal to be measured is applied, a timer counter having a latch function to which a frequency signal to be measured is applied, a counter value from the event counter and the The microprocessor includes a microprocessor that reads the count value of the timer counter at a constant cycle, and the microprocessor reads the counter value (Mo) from the event counter that was read previously, the count value (No) of the timer counter, and the current read value. The counter value (M1) from the event counter and the count value (N1) of the timer counter are used to calculate the frequency (Fi) of the signal to be measured by performing the operation shown in the following equation. It is a characteristic frequency signal measuring device. Fi = {(M1-Mo) / (N1-No)} × (1 / Tt) where Tt is the clock cycle of the timer counter

[0005]

[Action]

 The event counter and the timer counter both input the frequency signal to be measured, and the timer counter latches the counter value at each edge of the input pulse. The microprocessor reads the counter value from the event counter and the count value of the timer counter at regular intervals and performs a predetermined calculation to obtain the frequency of the input pulse.

[0006]

【Example】

 Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a configuration block diagram showing an embodiment of the present invention. In the figure, 1 is a microprocessor, 2 is a timer counter to which a frequency signal Si to be measured is applied, and has a latch circuit 21 for latching the counter value at each edge of an input pulse. Reference numeral 3 is an event counter to which the frequency signal Si to be measured is applied and which counts the number of pulses. The microprocessor 1 and each of these counters 2 and 3 are connected via a data bus. In the microprocessor 1, 11 is a data reading means realized by software, which is configured to read the count value from the timer counter 2 and the counter value from the event counter 3 at a constant cycle. Reference numeral 12 is a memory composed of a RAM for storing the data read by the data reading means 11, and 13 is an arithmetic means realized by software, which is the data stored in the memory 12 or the data reading means 11 reads the data. It is configured to perform a predetermined calculation by using the counter value and the like. The memory 12 stores at least the previous value and the current value of the count value from the timer counter 2 and the counter value from the event counter 3, respectively. In addition, the calculating means 13 stores the counter value (Mo) from the event counter read in the previous time stored in the memory 12 and the count value (No) of the timer counter, and the counter value from the event counter read this time ( M1) and the count value (N1) of the timer counter are used to perform a difference operation and a division operation.

The operation of the apparatus thus configured will be described below. FIG. 2 is a time chart showing an example of the operation. In this figure, (a) is a waveform diagram of the frequency signal (input pulse) to be measured, and its pulse width is Ti. The timer counter 2 counts an internal clock (assumed to be a cycle Tt) as shown in (b), and the count value No is latched by the latch circuit 21 at the trailing edge of the input pulse. Also, the event counter 3 counts the input pulse number by counting up the value like Mo, Mo + 1, Mo + 2 ... Every time the falling edge of the input pulse is detected as shown in (c) (count). is doing. The data reading means 11 of the microprocessor 1 reads the counter value of the timer counter 2 latched by the latch circuit 21 and the counter value of the event counter 3 at a constant cycle Tr. That is, for example, at the first read time To, the count value (latched value) No of the timer counter 2 and the count value Mo of the event counter 3 are read, and at the next read time T1 after Tr. , The count value (latch value) N1 of the timer counter 2 and the count value M1 of the event counter 3 are read. These read values are stored in the memory 12 so that they can be used for the calculation by the calculation means 13.

The calculation means 13 reads the counter value (Mo) from the event counter read in the previous time stored in the memory 12, the count value (No) of the timer counter, and the data read means 11 read this time. Using the counter value (M1) from the event counter and the count value (N1) of the timer counter, the frequency Fi (Hz) of the input pulse is calculated by performing the calculation as shown in equation (1). Fi = {(M1-Mo) / (N1-No)} * (1 / Tt) (1) where Tt is the clock cycle of the timer counter, and the frequency of the input pulse Fi (Hz) is calculated by performing such a calculation. The reason for obtaining is as follows. Within the constant period Tr in which the data reading means 11 in the microprocessor 1 reads the counter values of the counters 2 and 3, the measuring time TM of the input pulse of the event counter 3 is calculated from the count value of the timer counter 2, It can be expressed by equation (2). TM = (N1-No) * Tt (2) The pulse width Ti of the input pulse can be expressed by the equation (3) from the count value of the event counter 3. Ti = TM / (M1-Mo) (3) Substituting equation (2) for TM in equation (3) yields equation (4). Ti = {(N1-No) / (M1-Mo)} * Tt (4) Since the frequency Fi of the input pulse is the reciprocal of the pulse width Ti, the reciprocal of the equation (4) is calculated as (1). The equation is obtained, and the frequency of the input pulse can be obtained.

Since the microprocessor 1 has only to read the value of each counter in a constant cycle Tr, the load is reduced. Here, the accuracy of the frequency measurement depends on the clock cycle Tt of the timer counter 2 and the data read cycle Tr of the microprocessor 1. Whether the clock cycle Tt of the timer counter 2 is shortened (the clock frequency is increased). By increasing the data reading period Tr, the measurement accuracy can be increased.

FIG. 3 is a diagram showing the frequency measurement accuracy of the device of the present invention in relation to the frequency of the input pulse. In this example, the clock cycle Tt of the timer counter 2 is 0.5 μS, and the data read cycle Tr of each counter is 4 mS. As is clear from this diagram, the measurement accuracy is constant at (Tt / Tr) × 100 (%) above the input frequency (1 / Tr) (Hz) and (Tt below the input frequency (1 / Tr). / Ti) × 100 (%), and the accuracy is improved in proportion to the input frequency.

[0011]

[Effect of the device]

 As described in detail above, according to the present invention, highly accurate frequency measurement can be performed in a wide range from a low frequency signal to a high frequency signal without imposing a heavy burden on the microprocessor. A frequency signal measuring device can be realized.

[Brief description of drawings]

FIG. 1 is a configuration block diagram showing an embodiment of the present invention.

FIG. 2 is a time chart showing an example of operation.

FIG. 3 is a diagram showing the frequency measurement accuracy of the device of the present invention in relation to the frequency of an input pulse.

FIG. 4 is a conceptual diagram of a configuration of a conventional frequency signal measuring device using a microprocessor.

FIG. 5 is a conceptual diagram of a configuration of a conventional frequency signal measuring device using a microprocessor.

[Explanation of symbols]

 1 Microprocessor 2 Timer Counter 21 Latch Circuit 3 Event Counter 11 Data Reading Means 12 Memory 13 Arithmetic Means

Claims (1)

[Scope of utility model registration request] 1. An event counter to which a frequency signal to be measured is applied, a timer counter having a latch function to which a frequency signal to be measured is applied, a counter value from the event counter and a count value of the timer counter. And a microprocessor for reading in a fixed cycle, wherein the microprocessor reads the counter value (Mo) from the event counter read last time, the count value of the timer counter (No), and the count value from the event counter read this time. A frequency signal measuring device characterized by using a counter value (M1) and a count value (N1) of a timer counter to calculate a frequency (Fi) of a signal to be measured by performing an operation represented by the following formula. Fi = {(M1-Mo) / (N1-No)} × (1 / Tt) where Tt is the clock cycle of the timer counter