JP2000338144A - Calibration method of peak-to-peak voltage measuring device and peak-to-peak voltage measuring device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inexpensively calibrate by determining an offset coefficient of a measurement signal path while applying the common potential to an input terminal of the measurement signal path, intermitting the DC voltage while applying the existing DC voltage to the input terminal to produce a pulse signal, and determining the AC gain coefficient of the measurement signal path on the basis of the pulse signal. SOLUTION: An excitation switch S6 is mounted on a calibration circuit 8, and excited by an excitation signal of about 1 kHz from a processor 6 for alternately switching the contacts (a), (b) at a repeating speed of about 1 kHz. By this operation, a pulse variable between the common potential and the voltage VR determined on a DC power source 11A, is generation on the input terminals of the range amplifiers A1, A2. An AC gain coefficient and an offset coefficient are determined by utilizing this pulse. On this occasion, the calibration is executed by converting the mode change-over switches S1, S2 into the contact (b), the range change-over switches S3, S5 are converted into the contact (a), and a change-over switch S7 is converted into the contact (a).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of calibrating a peak-to-peak voltage measuring device for measuring the peak-to-peak voltage of an AC signal, and a peak-to-peak voltage measuring device which is operated by being calibrated by the method.

[0002]

2. Description of the Related Art FIG. 5 shows a configuration of a conventional peak-to-peak voltage measuring device. The signal under test Vm input to the input terminal Tin is input to the range amplifiers A1 and A2 through the DC cut capacitor 1. The range changeover switch S3 is connected to the output side of the range amplifiers A1 and A2, and is input to the peak hold circuit 4 through the range changeover switch S3 and the DC cut capacitor 3.

The peak-to-peak voltage Vp-p held by the peak-to-peak voltage holding circuit 4 is a peak-to-peak hold voltage, and is output as a DC voltage. This DC voltage is input to the AD converter 5 and is converted to an AD converter. The digital signal is subjected to A / D conversion at 5 and taken into an arithmetic processing unit 6 comprising a microcomputer. The captured peak-to-peak voltage is displayed on the display 7 as a measured value.

As shown in FIG.
Signal V swinging positive and negative around a common potential of 0 V_AC1
And the DC voltage V as shown in FIG._DCAC signal superimposed on
Issue V _AC2Peak-to-peak voltage V_P−_P2When measuring
There is. DC voltage V shown in FIG. 6B_DCAC signal superimposed on
Issue V_AC2Peak-to-peak voltage V_P-P2To measure
The presence of a flow cut capacitor is essential. Therefore
As shown in FIG. 5, a conventional peak-to-peak voltage measuring device
But DC cut capacitors 1 and 3 are connected in series with the measurement signal path
Connected, and that the DC voltage is input to the AD converter 5.
It is configured to block.

As shown in FIG. 5, since DC cut capacitors 1 and 3 are conventionally connected in series to a measurement signal line for peak-to-peak voltage measurement, when calibration is performed, an AC standard voltage is used. Is input to the input terminal Tin, and the AC gain coefficients KG ₁ , KG ₂ and the offset coefficients KF _1, KF ₂ of the measurement signal path are calculated by the measurement signal path based on the input known AC voltage signal. Gain coefficient KG
₁ , KG ₂ and offset coefficients KF _1, KF ₂ are stored and the actual display value Y is (first range) Y ₁ = KG ₁ · V ₁ + KF ₁ (second range) Y ₂ = KG ₂ · V ₂ + KF ₂ (V _{1 and} V ₂ are the values obtained by AD conversion of the actual peak and peak voltages to be measured) and displayed.

The AC gain coefficients KG ₁ and KG ₂ are obtained as follows. In the case of range 1, the AD conversion value x when a known AC voltage y _f1 near the full scale is input
_f1 and A when a known AC voltage _yz1 near zero is input
D converted value KG ₁ and KF ₁ from x _z1 becomes _{KG 1 = (y f1 -y z1} ) / (x f1 -x z1) KF 1 = x z1 -y z1 / KG 1.

[0007] When the range 2, obtained by _{KG 2 = (y f2 -y z2} ) / (x f2 -x z2) KF 2 = x z2 -y z2 / KG 2. Thus, the conventional AC voltage y _f1 as calibration for each _{range, y z1, y f2, y} z2 is generated, the gain coefficient K by the AC voltage y _f1, y _z1 and y _f2, y _z2
Seeking _{G 1, KF 1, KG 2} , KF 2.

[0008]

As described above, the peak-to-peak voltage measuring apparatus requires AC calibration voltages y _f1 , y _z1 , y _f2 and y _z2 for each measurement range. However, since the AC voltage generator is expensive, there is a disadvantage that the user who uses the peak-to-peak voltage measuring apparatus is burdened with an economic burden.

An object of the present invention is to provide a method for calibrating a peak-to-peak voltage measuring apparatus which can perform calibration at a low cost by using a DC voltage source as a calibration signal source, and a peak-peak capable of being calibrated by this calibration method. It is intended to provide a voltage measuring device.

[0010]

According to the present invention, a DC cut capacitor and a peak hold circuit for outputting a DC voltage corresponding to a peak-to-peak voltage of an AC signal to a measurement signal path, and a DC voltage output by the peak hold circuit AD
And a peak-to-peak voltage measuring device configured to convert the peak-to-peak voltage of the signal under measurement into a digital value in the AD converter, and to display the digital value on a display. Applying a common potential to the input terminal of the measurement signal path in the calibration mode, similarly applying a known DC voltage to the input terminal of the measurement signal path, and applying a common potential to the input terminal. Determining a path offset coefficient KF ₁ , KF ₂ , generating a pulse signal by intermittently applying a DC voltage having a known value,
A peak-to-peak voltage measuring apparatus for executing a step of obtaining an AC gain coefficient of a measurement signal path from the pulse signal and a step of storing the AC gain coefficient and the offset coefficient obtained in each of these steps. Is proposed.

According to the present invention, in a peak-to-peak voltage measuring device having a structure in which a range changeover switch is provided in a measurement signal path, a known DC voltage value is reduced to 1 / N when calibrating a range having N times higher sensitivity. The present invention proposes a method for calibrating a peak-to-peak voltage measuring apparatus in which an attenuator is connected and the same DC voltage source is used to calibrate a range having N times higher sensitivity.

In the present invention, there is further provided a DC application circuit for bypassing the DC cut capacitor and the peak hold circuit in the calibration mode for obtaining the AC gain coefficient KG ₂ of the second range having high sensitivity. DC gain coefficient AG 1 of _each, AG ₂ and obtains a DC offset coefficient AF _1, AF _2, and the DC gain factor and DC offset coefficients, AC gain coefficient K obtained in claim 1
AC gain coefficient KG _{2 in a} range with higher sensitivity than G ₁
Is calculated by KG ₂ = (AG ₂ / AG ₁ ) · KG ₁ , and a method of calibrating the peak-peak voltage measuring device is proposed.

A peak-to-peak voltage measuring apparatus according to the present invention comprises an excitation switch connected in series to a measurement signal line in a calibration mode on an input side of a measurement signal line, and a DC voltage connected to an input terminal of the measurement signal line. A variable attenuator that can be switched between a state in which the voltage of the source is output as it is, a state in which the voltage is attenuated to 1 / N, and a DC voltage for calibration selected and taken out by the range switch are directly supplied to the AD converter. The present invention proposes a peak-to-peak voltage measuring device having a configuration provided with a DC application circuit.

According to the method for calibrating a peak-to-peak voltage measuring apparatus according to the present invention, a pulse is generated by intermittently applying a DC voltage having a known voltage, and this pulse is used to generate an AC gain coefficient KG ₁ for each range _. KG ₂ and offset coefficient K
Since F _{1 and} KF ₂ are obtained and stored, it is possible to calibrate the peak-to-peak voltage measuring device without preparing an AC standard signal source. Therefore, there is an advantage that the cost required for the calibration can be reduced.

Further, according to the present invention, in a mode for calibrating a high-sensitivity range, a DC voltage applied to an input terminal is directly input to an AD converter by bypassing a DC cut capacitor and a peak hold circuit by a DC application circuit. Suggest calibration method for determining the DC gain coefficient AG ₁ and AG ₂ range. When this calibration method is used, the calibration of the high sensitivity range is performed by direct current, so that the influence of noise generated by pulsing can be reduced, and in this respect, the advantage that the accuracy of the calibration can be improved can be obtained. .

[0016]

FIG. 1 shows an embodiment of the present invention. In FIG. 1, parts corresponding to those in FIG. 5 are denoted by the same reference numerals. In the present invention, the mode changeover switches S1, S2 are connected between the input terminal Tin and the range amplifiers A1, A2.
And the state in which the DC cut capacitor 1 is selected by the mode changeover switches S1 and S2, and the calibration circuit 8
Is switched to a selected state.

More specifically, in the calibration mode, the input terminal T
is connected to the calibration voltage source 11, and the calibration voltage source 1
1 to the input terminal Tin, and applies the DC calibration voltage to the excitation switch S provided in the calibration circuit 8.
6, a pulse signal is generated by the intermittent operation, and calibration is performed using the pulse signal.

The calibration power supply 11 includes a variable DC voltage source 11A capable of outputting a desired voltage, a state in which the voltage VR of the DC voltage source 11A is applied to the input terminal Tin, and a common potential applied to the input terminal Tin. And a changeover switch S7 that switches to a state in which The calibration circuit 8 is selectively connected to the measurement signal path by mode changeover switches S1 and S2. That is, when the mode changeover switches S1 and S2 are switched to the contact point a, the peak / peak voltage measurement mode is set. In this case, the DC cut capacitor 1 is connected to the measurement signal path.

When the mode changeover switches S1 and S2 are changed to the contact b, a calibration mode is set. In this case, a calibration circuit 8 is inserted in series in the measurement signal path. Calibration circuit 8
Is composed of an excitation switch S6 and an attenuator ATT. The attenuator ATT is provided with a selection switch S5,
When the contact a is selected, the voltage VR input to the input terminal Tin is sent to the mode switch S2 as it is. When the contact b is selected, the voltage V input to the input terminal Tin is
R is divided by 1 / N and sent out to the mode switch S2.

The mode switches S2 are connected to the range amplifiers A1 and A2, and the output terminals of the range amplifiers A1 and A2 are connected to the contacts a and b of the range switch S3, respectively. In this example, the range amplifier A1 has an amplification of one time,
In this example, the range amplifier A2 has a 10-fold amplification factor.
Therefore, the attenuator ATT described above is set to an attenuation ratio that attenuates the input voltage to 1/10 when the switch S5 is switched to the contact b.

A series circuit of a DC cut capacitor 3 and a peak hold circuit 4 is connected to the subsequent stage of the range change switch S3. The output voltage signal of the peak hold circuit 4 is input to the AD converter 5 and AD-converted to perform an AD conversion.
Is input to In the normal measurement mode, the mode changeover switches S1 and S2 are changed to the contact a, and the range changeover switch S3 is changed to the contact a or b according to the level of the signal to be measured, corresponding to the peak-to-peak voltage of the signal to be measured. The DC voltage is output from the peak hold circuit 4, and this DC voltage is AD-converted by the AD converter 5, input to the arithmetic processing device 6, and displayed on the display 7.

The present invention proposes a calibration method for calibrating a peak-to-peak voltage measuring device including a peak hold circuit 4 using a DC calibration voltage source 11. That is, an excitation switch S6 is provided in the calibration circuit 8, and the excitation switch S6 is excited by, for example, an excitation signal of about 1 KHz from the arithmetic processing unit 6 and alternately switches to the contacts a and b at a repetition rate of 1 KHz. By this conversion operation, the input terminals of the range amplifiers A1 and A2 are connected to the common potential and the DC power supply 11.
A pulse that changes between the voltage VR set to A and the voltage VR is applied. Using these pulses, the AC gain coefficients KG _{1 and} KG
₂ and offset coefficients KF _{1 and} KF ₂ are obtained.

For this purpose, the mode changeover switches S1, S
Calibration of the first range is performed in a state where 2 is changed to the contact b, the changeover switch S7 is changed to the contact a, and the range changeover switches S3 and S5 are changed to the contact a. This calibration exchange as in the conventional art gain factor KG ₁ and the offset coefficient KF ₁ to _{KG 1 = (y f1 -y z1} ) / (x f1 -x z1) KF 1 = x z1 -y z1 / KG 1 y _f1 : peak-to-peak voltage corresponding to full scale (when the first range is 100 mVp-p in full scale, the voltage to be set to 11 A of the DC voltage source is set to 100 mV using an accurate voltmeter. value is y _f1) y _z1: DC input voltage value of the value corresponding to zero, thus y _z1
= 0 x _f1: the output value of the AD converter 5 when inputting y _f1 x _z1: obtaining an output value of the AD converter 5 when inputting y _z1. To obtain x _z1 , the switch S7 is changed to the contact b.

The AC gain coefficient KG ₂ and the offset coefficient KF ₂ of the _second range are determined by the range changeover switches S3 and S5.
The switched to the contact b, obtained by KG ₂ = as in the first range _{(y f2 -y z2) / (} x f2 -x z2) KF 2 = x z2 -y z2 / KG 2.

Accordingly, in the present invention, since the calibration can be performed using the DC calibration voltage source 11, there is an advantage that the calibration can be performed with an inexpensive device. by the way,
In FIG. 1, the AC gain coefficient KG ₂ is obtained by using the pulse generated by the excitation switch S6 also in the second range having high sensitivity. However, in practice, noise is generated at the rising and falling timings of the pulse, and the sensitivity is reduced. In the high range, the error due to noise tends to be large.

For this reason, according to the present invention, in the range of high sensitivity, the excitation switch S6 is stopped in a state of being changed to the contact a, and a DC application circuit 9 and a changeover switch S4 are further provided as shown in FIG. 9, the voltage VR of the calibration power supply 11 passed through the measurement signal path to the AD converter 5.
Directly applied, thereby obtains a DC gain coefficient AG ₁ and AG ₂ of the first range and the second range, the AC gain factor KG ₂ sensitivity by the DC gain coefficient AG ₁ and AG ₂ is higher second range KG ₂ = also proposes a calibration method for calculating the _{(AG 2 / AG 1) KG} 1.

The reason why the AC gain coefficient KG ₂ of the second range can be obtained by DC calibration will be described below. Set the gain of range amplifier A1 to G _a1 and the offset to O
_a1 , the gain of the range amplifier A2 is G _a2 , and the offset is O.
_a2, peak hold the gain of the circuit 4 Gb, Ob offset, gain Gc of direct current application circuit 9, Oc an offset, the value of the first and the input side of the signal of the second range amplifier A1, A2 x _1, range Assuming that the value of the signal on the output side of the amplifiers A1 and A2 is x ₂ , the output value of the AD converter 5 is V _1, V _2, and the measurement value sent to the display 7 is y, In the range, x ₂ = G _a1 · x ₁ + O _a1 V ₁ = G _b · x ₂ + O _b = G _b · G _a1 · x ₁ + G _b · O _a1 + O _b V ₁ is used as the calibration coefficients KG ₁ and KF ₁ y for computing result to display the same value as the true value x ₁ of the input _{1 = KG 1 V 1 + KF} 1 = KG 1 · G b · G a1 · x 1 + KG 1 (G b · O a1 + O b _{) + KF 1 = x 1 KG} 1 = 1 / (G b · G a1), KF 1 = -KG 1 (G b · O a1 + O b) ·· (1) in the same manner in the second range Range conversion switch S3 to the contact b) KG ₂ = 1 / a second range _{(G b · G a2),} KF 2 = -KG 2 (G b · O a2 + O b) ·· (2) DC calibration where Execute Switches S1, S2, S4
To the contact b, the switches S3 and S5 to the contact a and the switch S
6, S7 in the first range in a state set to the contact a is _{x 2 = G a1 · x 1} + O a1 V 2 = G c · x 2 + O C = G c · G a1 · x 1 + G c · O a1 + O _c Set the DC calibration gain coefficient to AG ₁ and the offset coefficient to AF
₁ to the _{AG 1 = 1 / (G c} · G a1), AF 1 = -AG 1 (G c · G a1 + O c) ·· (3) Range switch S3 is similarly (second range in the second range When converting an S5 to contact _{b) AG 2 = 1 / (} G c · G a2), AF 2 = -AG 2 (G c · G a2 + O c) ·· (4) (1), (2), ( _{3), (4) KG 2} / KG 1 = G a1 / G a2 = AG 2 / AG 1 KG 2 = (AG 2 / AG 1) KG 1 because consisting equation, dc is the seek AC gain KG ₂ gain coefficient AG _1, may be obtained and AG _2.

[0028] Since AG ₁ is a DC gain factor for the first range, switches S1, S2, S4 contacts b, and switches S3, S5 and set the contact a switch S6 to the contact a, the standard voltage VR to the input terminal Tin type and a common potential, obtains the DC gain coefficient AG ₁ and the offset coefficient AF ₁ by the following equation. _{AG 1 = (y df1 -y dz1} ) / (x df1 -x dz1) AF 1 = x dz1 -y dz1 / AG 1 y df1: voltage VR of the DC voltage source 11A which is set to the full-scale value of the first range the value y _dz1: at zero input voltage x _df1: y AD conversion value when inputting _df1 x _dz1: obtaining a DC gain factor AG ₂ of the AD conversion value then the second range when entering y _dz1.

The DC gain coefficient AG ₂ of the second range is also equal to the first range.
It is obtained in the same way as the DC gain coefficient AG _{1 of the} range,
Since the signal passes through the attenuator ATT in the second range, the attenuator ATT
(The true value of the output of the attenuator ATT) must be obtained. Switches S1, S2 and S4 are set to contact b, switch S
3 contacts a, the switch S5 is set contact b, and switch S6 to the contact a, AG ₁ and AF obtained in the calibration of the first range
_{Using 1} , the true values y _df2 and y _dz2 of the output of the attenuator ATT are _obtained .

Y _df2 is the attenuator AT at full scale input
The true output value of T, y _dz2, is the true value of the output of the attenuator ATT at zero. y _df2 and y _dz2 are obtained by the following equations. _{y df2 = AG 1 · x df1} '-AF 1 y dz2 = AG 1 · x dZ1' -AF 1 x df1 ': Enter the y _df1, AD conversion value when measuring the attenuator ATT output in the first range x _dZ1 ': y _dZ1 is input, and the AD conversion value when the output of the attenuator ATT is measured in the first range. Further, x _df2 and x _dz2 are obtained. x _df2 is an output value of the AD converter 5 when y _df2 is input and measured in the second range, and x _dz2 is an output value of the AD converter 5 when y _dz2 is input and measured in the second range.

By obtaining these, the DC gain coefficient AG ₂ and DC offset coefficient AF of the second range are obtained.
₂ is obtained by AG ₂ = (y _df2 −y _dz2 ) / (x _df2 −x _dz2 ) AF ₂ = x _dz2 −y _dz2 / AG ₂

The AC gain factor KG ₂ of the second range by a DC gain factor AG ₂ of the second range is determined is obtained by _{KG 2 = (AG 2 / AG} 1) · KG 1. KF ₂ uses the switches S1, S2, and S4 as contacts a, the switch S3 as contacts b, the switch S7 as contacts b, applies a common potential to the input Tin, performs peak-peak measurement in the second range, and obtains the following formula. .

[0033] _{KF 2 = x z2 -y z2 /} KG 2 y z2: DC input voltage having a value corresponding to zero thus y _z2 = 0 x _z2: AD conversion value of these coefficients KG ₁ when inputting y _{z2 ,} by storing in KG _2, and KF _1, KF ₂ the storage device of the processing unit 6, for measurement values V ₁ and V ₂ which is AD converted by the AD converter 5 in the normal measurement mode, Show measurements calibrated by correcting the display value Y _1, Y ₂ (first _{range) Y 1 = KG 1 · V} 1 + KF 1 ( second _{range) Y 2 = KG 2 · V} 2 + KF 2 can do.

FIG. 3 shows an outline of a program for executing the DC calibration mode. A step offset coefficients of the first range by ~ KF _1, KF _2, AC gain coefficient AG _1,
A DC offset coefficient AF _1, the attenuator ATT of the true output values y _df2, y _dz2 DC gain coefficient AG ₂ of the second range is determined. The program for executing this calibration operation is automatically executed by operating the command switch of the calibration mode with the calibration voltage source 11 connected to the input terminal Tin. The order of steps 1 to 4 may be interchanged.

FIG. 4 shows a modification of the embodiment shown in FIG. This embodiment proposes a configuration in which a filter 8A including a resistor R and a capacitor C and a buffer amplifier A3 are provided in a stage preceding the excitation switch S6. By providing the filter 8A, the calibration voltage source 1
This eliminates noise mixed in from No. 1 and provides an effect that the calibration operation can be executed in a stable state.

In the above description, the case where the range is set to two stages has been described. However, the present invention is not limited to the case where the range is changed to two stages and the DC gain coefficient and the DC offset coefficient AG _{2 of} each range can be changed. _, AF2 _, AG3 _, AF3 _, ..., It can be easily understood that the AC gain coefficients of all ranges can be obtained.

[0037]

As described above, according to the present invention, since the calibration can be performed by using the DC calibration voltage source 11, there is an advantage that it is not necessary to prepare an expensive device such as an AC signal source for the calibration. can get. Furthermore, calibration of the range with high sensitivity,
In the case of a configuration using a direct current, the effect of noise generated due to pulsing can be reduced, and there is an advantage that accurate calibration can be performed.

[Brief description of the drawings]

FIG. 1 is a block diagram for explaining an embodiment of the present invention.

FIG. 2 is a block diagram showing an embodiment to which a function of executing a DC calibration mode according to the present invention is added.

FIG. 3 is a flowchart for explaining an outline of a program used for a calibration method according to the present invention.

FIG. 4 is a block diagram for explaining a modified embodiment of the present invention.

FIG. 5 is a block diagram for explaining a conventional technique.

FIG. 6 is a waveform chart showing a measurement situation of a peak-peak voltage.

[Explanation of symbols]

 1, 3 DC cut capacitors A1, A2 Range amplifier 4 Peak hold circuit 5 AD converter 6 Arithmetic processing unit 7 Display 8 Calibration circuit ATT Attenuator S1, S2, S4 Mode switch S2, S3, S5 Range switch S6 Excitation switch 11 Voltage source for calibration

Claims (4)

[Claims] 1. A peak hold circuit that outputs a DC cut capacitor and a DC voltage corresponding to the peak and peak voltages of an AC signal to a measurement signal path, and an AD converter that AD converts the DC voltage output by the peak hold circuit. Applying a common potential to an input terminal of the measurement signal path in a calibration mode in the peak-to-peak voltage measurement apparatus having a configuration including: and providing a DC voltage, and determining an offset coefficient KF ₁ of the measuring signal pathways while providing a common potential to said input terminal, said known DC voltage pulse signal by intermittently the DC voltage in a state which gives Generating an AC gain coefficient K of the measurement signal path by using the pulse signal.
Determining a G _1, method for calibrating a peak-to-peak voltage measuring apparatus characterized by performing the steps, the storing the AC gain factor and offset coefficients obtained by these steps. Wherein the digital values V ₁ output from the AD converter with the AC gain factor KG ₁ and the offset coefficient KF ₁ as determined by calibration method of the peak-to-peak voltage measuring device according to claim 1 KG ₁ & A peak-to-peak voltage measuring device, wherein the display is corrected by V ₁ + KF ₁ and displayed. 3. The calibration method for a peak-to-peak voltage measuring apparatus according to claim 1, wherein the range switching switch is connected to the measurement signal path, and the range switching switch is connected to the peak hall circuit and a DC cut capacitor. And a DC application circuit for directly inputting the signal of each range selected in the above-described AD converter to the AD converter, applying the known DC voltage to the input terminal of the measurement signal path, and applying the DC voltage in the applied state of the DC voltage. DC gain coefficient AG for first range and second range
₁ , AG ₂ and their DC gain coefficients A
By using G ₁ and AG ₂ , the AC gain coefficient KG ₂ is calculated as KG ₂ =
(AG ₂ / AG ₁ ) A method for calibrating a peak-to-peak voltage measuring device, wherein the value is obtained and stored by KG ₁ . 4. An AC gain coefficient KG ₂ obtained by the method for calibrating a peak-to-peak voltage measuring device according to claim 3.
A peak-to-peak voltage measuring device, wherein a digital value V ₂ output from an AD converter is corrected by KG ₂ · V ₂ -KF ₂ and displayed using an offset coefficient AF ₂ .