JP2005091206A - Instrument and method for measuring pulse width - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive instrument and method for measuring a pulse width excellent in maintainability requiring no special calibration work for environmental fluctuation factors represented by a temperature change. <P>SOLUTION: This pulse duration measuring instrument of the present invention has a pulse generation part for generating a predetermined duration of reference signal, a switch input with the reference signal and a measured signal that is a pulse having an optional duration, and for selecting one of the signals to be output, a time voltage conversion part input with the signal selected by the switch and for outputting a voltage in response to the duration of the pulse thereof, an analog/digital converter for converting the voltage output from the time voltage conversion means into a digital value, and a control part for controlling the switch to measure the first digital value in response to the duration of the reference signal and the second digital value in response to the duration of the measured signal, and for drawing out information of the duration of the measured signal, based on the first digital value and the second digital value. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a pulse time width measuring apparatus and a pulse time width measuring method.

  In various electronic devices, the time width of an input pulse is measured. A conventional pulse time width measuring apparatus will be described with reference to FIGS. FIG. 3 is a block diagram showing a configuration of a conventional pulse time width measuring apparatus, and FIG. 4 is a diagram showing waveforms of respective signals. In FIG. 3, the time-voltage conversion of the conventional example is a constant current circuit 3, a current limiting resistor 4, a capacitor 5, a switch 6, a sample hold unit 7, and an analog / digital converter (abbreviated as A / D converter) 8. And a control unit 9. In the conventional example, the control unit 9 is a microcomputer. In FIG. 4, reference numeral 12 denotes a pulse signal which is a signal under measurement, and 13 denotes a voltage waveform at a connection point between the resistor 4 and the capacitor 5 when the pulse signal is input. 14 is a diagram schematically showing how the voltage waveform at the connection point between the resistor 4 and the capacitor 5 changes according to the change in the environmental temperature when the same signal under measurement (pulse signal) 12 is input. .

The constant current source 3 outputs a constant current I. The capacitor 5 is charged with a constant current I through the resistor 4. The switch 6 connects both ends when the signal under measurement 12 is Low level, and opens both ends when the signal under measurement 12 is High level. The capacitor 5 is charged by the constant current source 3 while the signal under measurement 12 is at a high level. The voltage V across the capacitor 5 (the voltage at the connection point between the resistor 4 and the capacitor 5) at the trailing edge of the period when the signal under measurement 12 is at the high level is Q, the amount of electricity stored in the capacitor 5 at that time is Q, and the constant current Assuming that the constant current value output from the source 3 is I, the capacitance of the capacitor 5 is C, and the time width of the pulse signal (period of high level) is T, it can be expressed by the following equation.
Q = I ・ T = C ・ V (1)

The sample hold unit 7 samples and holds the voltage V across the capacitor 5 at the trailing edge of the period in which the signal under measurement 12 is at the high level. The sample hold unit 7 holds and outputs the peak value of the voltage V across the capacitor 5. The A / D converter 8 converts the voltage sampled and held by the sample hold unit 7 into, for example, an 8-bit digital signal.
T = (C / I) · V (2)
Since I and C are fixed values, the period T during which the pulse signal as the signal under measurement is at a high level is proportional to the digitally converted voltage value V. When the pulse time width measuring device is manufactured at the factory, the proportionality constant K = C / I is set to a predetermined value. The controller 9 can derive an accurate time width T based on the equation (2) by measuring the voltage value V. The control unit 9 executes a predetermined process based on the derived time width T.

Japanese Patent Laid-Open No. 7-280857 discloses a conventional time-voltage conversion circuit using resistors and capacitors.
JP 7-280857 A JP 59-97077 A

  However, the above formula is applied only when each element operates stably in a constant ambient environment. Actually, the resistance value of the resistor 4 and the capacitance of the capacitor 5 as well as the characteristics of the transistors constituting the constant current circuit 3 change mainly due to temperature changes in the operating state. Due to these influences, the supply current amount I changes, and the voltage value V varies according to the environmental temperature. This is shown at 14 in FIG.

  It is also possible to arrange a temperature measuring element in the vicinity of the resistor 4 and the capacitor 5 and store a correspondence table between the detected temperature of the temperature measuring element and the proportional constant K at each temperature in the pulse time width measuring device. During operation, the control unit 9 acquires information about the detected temperature from the temperature measuring element, and selects a proportional constant K corresponding to the temperature from the storage unit. The control unit 9 multiplies the output value of the A / D converter 8 by the selected proportionality constant K to obtain the time width of the period during which the signal under measurement (one or periodic) is at the high level. As for the deterioration of the capacitance of the capacitor over time, there was only an appropriate measure for the pulse time width measuring device to update the storage proportionality constant every predetermined period.

However, in the conventional pulse time width measuring apparatus and pulse time width measuring method, it has been necessary to perform precise adjustment and calibration work over time during manufacturing. This pushed up the cost of the pulse duration measuring device. In addition, strict environmental temperature control and dedicated equipment for it were required during adjustment and calibration. Furthermore, periodic recalibration is necessary, and the maintainability is extremely poor.
The present invention solves the above-mentioned problems, does not require a temperature measuring element, etc., does not require calibration work during manufacturing and maintenance, is inexpensive and has excellent maintainability, and is a pulse time width that is not easily affected by environmental temperature. It is an object to provide a measuring apparatus and a pulse time width measuring method.

In order to solve the above problems, the present invention has the following configuration. According to the first aspect of the present invention, there is provided a pulse generator that generates a reference signal that is a single pulse having a predetermined time width or a pulse having periodicity, and a single or an arbitrary time width of the reference signal. A signal to be measured that is a pulse having periodicity is input, a switch that selects and outputs any one of the signals, a signal selected by the switch is input, and the time width of the pulse is input. A time voltage converter that outputs a voltage corresponding to the voltage, an analog / digital converter that converts the voltage output from the time voltage converter to a digital value, and the switch to control the time width of the reference signal. A first digital value and a second digital value corresponding to a time width of the signal under measurement are measured, and the time of the signal under measurement is measured based on the first digital value and the second digital value. Deriving width information A control unit that is a pulse time width measuring apparatus characterized by having a.
The present invention does not require a temperature measuring element or the like, does not require calibration work during manufacturing and maintenance, and can realize a pulse time width measuring device that is inexpensive and excellent in maintainability and is not easily affected by environmental temperature. Have

According to a second aspect of the present invention, there is provided a first time-voltage conversion step for generating a first voltage corresponding to a time width of a reference signal which is a single pulse having a predetermined time width or a pulse having periodicity. A first analog / digital conversion step for converting the first voltage into a first digital value, and a time width of a signal under measurement which is a single or periodic pulse having an arbitrary time width. A second time voltage conversion step for generating a second voltage; a second analog / digital conversion step for converting the second voltage into a second digital value; the first digital value and the second And a time width information generating step for deriving information on the time width of the signal under measurement based on the digital value of the pulse time width.
The present invention does not require a temperature measuring element or the like, does not require calibration work during manufacturing and maintenance, and can realize a pulse time width measurement method that is inexpensive and excellent in maintainability and is not easily affected by environmental temperature. Have

  According to the present invention, a temperature measuring element and the like are unnecessary, calibration work at the time of manufacture and maintenance is unnecessary, and a pulse time width measuring device and a pulse time that are inexpensive and excellent in maintainability and are not easily affected by environmental temperature. The advantageous effect that the width measuring method can be realized is obtained.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments that specifically show the best mode for carrying out the present invention will be described below with reference to the drawings.

<< Embodiment >>
A pulse time width measuring apparatus and a pulse time width measuring method according to an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a block diagram showing a configuration of a pulse width time measuring apparatus according to the present invention, and FIG. 2 is a diagram showing waveforms of respective signals. The pulse time width measuring apparatus according to the embodiment measures a period T in which a signal under measurement is at a high level.

  The pulse time width measuring apparatus according to the embodiment of the present invention includes a reference signal generator 1, a switch 2, a constant current source 3, a current limiting resistor 4, a capacitor 5, a switch 6, a sample hold unit 7, and an analog / digital converter. 8 and a control unit 9. In the embodiment, the control unit 9 is a microcomputer. For example, a pulse time width measuring circuit (having a function of counting pulses during a period when the input signal is at a high level) used in a microcomputer is used to measure the time width of another pulse signal. Cannot be used to measure the pulse width of the signal under measurement 12 (the period during which the signal under measurement 12 is at a high level), while the A / D converter 8 incorporated in the microcomputer is connected to the pulse width of the signal under measurement 12. Assume that it can be used to measure

  In FIG. 1, a reference signal generator 1 outputs a single or periodic pulse signal having a certain time width. The time width T0 of the pulse signal is not easily affected by the environmental temperature and the time. For example, the reference signal generator 1 generates and outputs a reference signal obtained by dividing the output signal of a crystal oscillator that stably oscillates at a constant frequency by a predetermined frequency division ratio. Preferably, the reference signal generator 1 is built in a microcomputer.

  The switch 2 receives the reference signal 11 output from the reference signal generator 1 and the signal under measurement 12 and outputs either one according to a command from the controller 9. In FIG. 2, 11 is a reference signal, 12 is a pulse signal which is a signal under measurement, 13 is a connection point between the resistor 4 and the capacitor 5 when the reference signal 11 and the signal under measurement 12 are input at two environmental temperatures. The waveform of voltage V (13) is shown typically. The output signal of the switch 2 is input to the control terminal of the switch 6 and the sample hold timing signal input terminal of the sample hold unit 7.

The constant current source 3 outputs a constant current I. The capacitor 5 is charged with a constant current I through the resistor 4. The switch 6 connects both ends when the reference signal 11 or the signal under measurement 12 is Low level, and opens both ends when the reference signal 11 or the signal under measurement 12 is High level. The capacitor 5 is charged by the constant current source 3 while the reference signal 11 or the signal under measurement 12 is at a high level. The voltage V across the capacitor 5 (the voltage at the connection point between the resistor 4 and the capacitor 5) at the trailing edge of the period in which the reference signal 11 or the signal under measurement 12 is at the high level is the amount of electricity stored in the capacitor 5 at that time. When Q is a constant current value output from the constant current source 3, C is a capacitance of the capacitor 5, and T is a time width of the pulse signal (high-level period), the following equation (1) is obtained.
Q = I ・ T = C ・ V (1)

The sample hold unit 7 samples and holds the voltage V across the capacitor 5 at the trailing edge of the period in which the reference signal 11 or the signal under measurement 12 is at the high level. The sample hold unit 7 holds and outputs the peak value of the voltage V across the capacitor 5. The A / D converter 8 converts the voltage sampled and held by the sample hold unit 7 into, for example, an 8-bit digital signal. The control unit 9 inputs a digital value.
The controller 9 controls the switch 2 to continuously measure and input the digital value V0 of the reference signal 11 and the digital value V of the signal under measurement 12.
T = (C / I) · V (2)
T0 = (C / I) · V0 (3)
Equation (4) is derived from equations (2) and (3).
T = (T0 / V0) · V (4)

Since T0 is known and is stable with respect to the environmental temperature and with time, the control unit 9 can calculate an accurate proportionality constant K = T0 / V0 by measuring the digital value V0. The control unit 9 can calculate an accurate time width T from the digital value V using the proportionality constant K. Since the control unit 9 continuously measures the digital values V0 and V, the two measured values are measured at almost the same ambient temperature. Therefore, the influence of environmental temperature is eliminated. Since the two measured values are measured using the capacitor 5, the influence of the deterioration of the capacitor 5 with time is eliminated in the equation (4).
Since T0 is substantially constant without adjustment work in the factory, it is not necessary to perform precise adjustment / calibration work in the factory to determine the proportionality constant K.
The control unit 9 performs a predetermined process based on the voltage value V converted into a digital signal.

Using FIG. 2 of FIG. 2, it will be described that the time width T derived by the control unit 9 is not affected by the environmental temperature. In FIG. 2, at the environmental temperature a, the digital value obtained from the reference signal 11 is V0a, the digital value obtained from the signal under measurement 12 is Va, and the time width that the control unit 9 derives using Equation (4) is shown. Ta. At the environmental temperature b, the digital value obtained from the reference signal 11 is V0b, the digital value obtained from the signal under measurement 12 is Vb, and the time width that the control unit 9 derives using Equation (4) is Tb. From the formula (4), the following formulas (5) and (6) are established.
The time width T0 is stable.
Ta = (T0 / V0a) · Va (5)
Tb = (T0 / V0b) · Vb (6)
As is apparent from 13 in FIG. 2, Va / V0a = Vb / V0b is established. Therefore, Ta = Tb is established. That is, the time width T derived by the control unit 9 is hardly affected by the environmental temperature.
The configuration of the embodiment is an exemplification, and may be any other configuration based on the idea of the present invention.

The block diagram which shows the structure of the pulse width time measuring apparatus in embodiment of this invention The figure which shows each part signal waveform of the pulse width time measuring apparatus in the form of the practice of this invention Block diagram showing the configuration of a conventional pulse time width measuring apparatus The figure which shows each part signal waveform of the pulse time width measuring apparatus of a prior art example

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Reference signal generation part 2, 6 Switch 3 Constant current source 4 Resistance 5 Capacitor 7 Sample hold part 8 Analog / digital converter 9 Control part (microcomputer)

Claims (2)

A pulse generation unit that generates a reference signal that is a single or periodic pulse having a predetermined time width;
A switch that inputs the reference signal and a signal under measurement that is a single or periodic pulse having an arbitrary time width, and selects and outputs any one of the signals;
A time voltage converter that inputs a signal selected by the switch and outputs a voltage corresponding to the time width of the pulse;
An analog / digital converter that converts the voltage output by the time voltage conversion means into a digital value;
The switch is controlled to measure a first digital value corresponding to the time width of the reference signal and a second digital value corresponding to the time width of the signal under measurement, and the first digital value And a control unit for deriving time width information of the signal under measurement based on the second digital value;
A pulse time width measuring apparatus comprising: A first time-voltage conversion step for generating a first voltage corresponding to a time width of a reference signal which is a single pulse having a predetermined time width or a pulse having periodicity;
A first analog / digital conversion step of converting the first voltage into a first digital value;
A second time-voltage conversion step of generating a second voltage according to the time width of the signal under measurement, which is a single or periodic pulse having an arbitrary time width;
A second analog / digital conversion step of converting the second voltage into a second digital value;
A time width information generating step for deriving time width information of the signal under measurement based on the first digital value and the second digital value;
A pulse time width measuring method characterized by comprising:

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