JPH0547872U - Frequency voltage converter - Google Patents

Abstract

(57) [Summary] [Purpose] To obtain an output voltage signal that accurately follows changes in the frequency of the input signal. An edge detecting means for detecting an edge of an input pulse, a counter means for measuring a time between the edges detected by the edge detecting means, and a predetermined calculation using time data measured by the counter means. Computing means for performing
A frequency-voltage conversion device comprising a signal output means for converting the calculation result obtained by the calculation means into a voltage signal and outputting the voltage signal, wherein the cycle (T) is sufficiently faster than the frequency of the input signal.
And a time width comparing means for comparing the time (tn) between the edges measured immediately before by the counter means and the time (tx) from the edge detected immediately before to the present time, and tx> In the case of tn, the control means controls the arithmetic means and the signal output means so as to calculate the output based on the frequency of (1 / tx) and output it as a voltage signal.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a frequency-voltage converter for converting a frequency signal into a voltage signal. More specifically, the pulse number signal output corresponding to the process amount is a standardized voltage signal such as 1 to 5V. The present invention relates to a frequency voltage conversion device that converts and outputs to.

[0002]

[Prior Art]

 For example, some transmitters that detect temperature, flow rate, etc. output frequency signals and pulse number signals related to these process quantities. Conventionally, as a device for converting the frequency of such a frequency signal or pulse signal into a voltage signal, for example, there is a device disclosed in Japanese Patent Laid-Open No. 63-172971.

This device includes a counter that counts the time between the rising and falling edges of an input frequency signal (pulse signal), an inverse computing means that finds the reciprocal of the count value obtained by the counter, and And a conversion means for converting the calculation result (digital data) into an analog voltage signal.

[0004]

[Problems to be solved by the device]

 In the conventional device having such a configuration, the output voltage signal Vo with respect to the input frequency signal Fin is, when the input frequency signal (pulse signal) rises or falls, as shown in FIG. However, there was an error only in the shaded areas with respect to the ideal output characteristics as shown by the broken lines.

This error becomes particularly large when the frequency of the input signal changes from a high state to a low state. The present invention has been made in view of the above circumstances, and an object thereof is to provide a frequency-voltage conversion device capable of obtaining an output voltage signal that accurately follows a change in the frequency of an input signal. To do.

[0006]

[Means for Solving the Problems]

 The present invention which achieves such an object is provided with an edge detecting means for detecting a rising or falling edge of an input signal, a counter means for measuring a time between the edges detected by the edge detecting means, and A frequency-voltage converter including a calculation means for performing a predetermined calculation using the time data measured by the counter means, and a signal output means for converting the calculation result obtained by the calculation means into a voltage signal and outputting the voltage signal. In addition, the counter operates at a cycle (T) that is sufficiently faster than the frequency of the input signal, and the time between the edges measured immediately before by the counter means (tn) and the edge detected immediately before are detected. In the time width comparison means for comparing the time (tx) from the current time to the present time, the time (tn) between the edges measured immediately before in the time width comparison means is the time (tn) to the current time. When it is judged to be smaller than x) (when tx> t n), the calculating means and the signal outputting means calculate the output based on the frequency of (1 / tx) and convert it into a voltage signal. And a control means for controlling so as to output the frequency-voltage converter.

[0007]

[Action]

 The time width comparison means detects that the frequency of the input signal changes in the lowering direction. The control means controls the calculation means and the signal output means so that the update period of the output voltage sent from the signal output means is sufficiently faster than the frequency of the input signal, and the frequency of the input signal decreases. If it changes, the output is calculated based on the frequency (1 / tx), and the output is converted into a voltage signal and output.

[0008]

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 an edge detecting means for detecting a rising or falling edge of an input signal (pulse signal) Fin, 2 is a counter means for measuring a time between the edges detected by the edge detecting means 1, Reference numeral 3 is an arithmetic means for performing a predetermined arithmetic operation using the time data measured by the counter means 2, which is composed of, for example, a microprocessor (CPU).

Reference numeral 4 denotes a signal output means for converting the calculation result obtained by the calculation means 3 into a voltage signal and outputting the voltage signal, which is configured to include a D / A converter therein. Reference numeral 5 is a time comparison means which operates in a cycle (T) which is sufficiently faster than the frequency of the input signal, and is the time (tn) between the edges measured immediately before by the counter means 2 and the time immediately before detected. It is configured to compare the time (tx) from the edge to the present time.

Reference numeral 6 denotes a control means, and when the time comparison means 5 determines that the time (tn) between the edges measured immediately before is shorter than the time (tx) up to the present time (tx). > Tn), the calculation means 3 and the signal output means 4 are controlled so as to calculate the output based on the frequency of (1 / t x) and output it as a voltage signal. The time comparing means 5 and the control means 6 are both realized by a program installed in the microprocessor CPU.

Reference numeral 7 denotes a memory, which stores time (tn, tn-1, tn-2, etc.) between edges measured by the counter means 2, data such as calculation constants used by the calculation means 3 and other programs. It is stored. The operation of the apparatus configured as described above will be described below. FIG. 2 is a time chart showing an example of the operation, and (a) shows a signal waveform of the input signal Fin to be converted into a voltage signal. The edge detecting means 1 detects, for example, a falling edge of the pulse of the input signal as shown in (b), and gives the edge detecting signal to the counter means 2. The counter means 2 measures time to, tn-1, tn between edges. The data relating to the respective times to, tn−1, tn measured here are sequentially stored in the memory 7.

The time comparison unit 5 stores the time (tn) data between the edge and edge measured immediately before stored in the memory 7, at a cycle T faster than the frequency of the read input signal, It is determined whether or not the time (tx> tn) from the edge detection time to the current time (comparison time) is longer (tx> tn), that is, whether or not the frequency of the input signal changes in the lower direction.

When the time width comparing means 5 determines that the time (tn) between the edges measured immediately before is smaller than the time (tx) up to the present time (tx). > Tn), the output is calculated to the calculation means 3 and the signal output means 4 based on the frequency of (1 / tx), and the output is converted into the voltage signal Vo and sent as shown in (c). Control.

FIG. 3 is a flowchart showing the operations of the time comparison means 5 and the control means 6. It is assumed that this flowchart is started at a cycle T faster than the frequency of the input signal Fin. When it is determined in step 1 performed by the time comparison means 5 that the time (tx) data up to the present time is larger than the time (tn) data between the edges measured last time (tx> tn), The control means 6 instructs the calculation means 3 to perform a calculation for converting the frequency of (1 / t x) into a voltage signal (step 2).

On the other hand, in step 1, the time (tx) up to the present time (tx is an integer multiple of the cycle T in which the flow chart of FIG. 3 is executed) is set between the edge and the edge measured last time. When it is determined that it is smaller than the time (tn) data (tx <tn), that is, when the frequency of the input signal does not change or indicates a direction in which it gradually increases, the control means 6 The operation means 3 is instructed to perform an operation for converting a frequency of (1 / tn) into a voltage signal (step 3).

FIG. 4 is a diagram showing a change in the voltage signal Vo output from the signal output means 4 when the frequency of the input signal changes in the lowering direction. At every cycle T in which the flowchart shown in FIG. 3 is executed, the voltage signal updated by the operation of converting the frequency of (1 / tx) into the voltage signal is sequentially output, and the frequency of the input signal is Even if the voltage changes in the direction of decreasing, it is possible to obtain a voltage signal that changes with characteristics close to ideal.

Although the edge detecting means 1 detects the falling edge of the pulse signal in the above embodiment, it may detect the rising edge of the pulse signal.

[0018]

[Effect of the device]

 As described in detail above, according to the present invention, it is possible to provide a simple frequency-voltage converter having a configuration capable of obtaining an output voltage signal that accurately follows a change in the frequency of an input signal. According to the present invention, for example, when the frequency range of the input signal is 0 to 1HZ, the output voltage signal can be made to have characteristics close to ideal by setting the cycle period T of the flowchart shown in FIG. 3 to 5 ms. I can do it.

[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 flowchart showing the operations of the time comparison means and the control means.

FIG. 4 is a diagram showing changes in the voltage signal Vo output from the signal output means when the frequency of the input signal changes in the direction of lowering.

FIG. 5 is a waveform diagram showing a state of an output voltage signal of a conventional device.

[Explanation of symbols]

 1 Edge Detection Means 2 Counter Means 3 Arithmetic Means 4 Signal Output Means 5 Time Comparison Means 6 Control Means 7 Memory

Claims (1)

[Scope of utility model registration request] 1. An edge detecting means for detecting a rising edge or a falling edge of an input signal, a counter means for measuring a time between edges detected by the edge detecting means, and a time measured by the counter means. A frequency-voltage conversion device comprising a calculation means for performing a predetermined calculation using data and a signal output means for converting the calculation result obtained by the calculation means into a voltage signal and outputting the voltage signal, wherein It operates in a cycle (T) that is sufficiently faster than the frequency, and displays the time (tn) between the edges measured immediately before by the counter means and the time (tx) from the edge detected immediately before to the present time. In the time width comparison means for comparing and the time width comparison means, the time (tn) between the edges measured immediately before is the time (tn) up to the present time.
When it is judged to be smaller than x) (when tx> tn), (1 / t
A frequency-voltage conversion device, comprising: a control means for calculating an output based on the frequency of x) and controlling the output so as to output the voltage signal.