JPH0772739B2 - Analog tester - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an analog tester for automatically discriminating and displaying polarity or alternating current and for pointing a terminal in a forward direction.

[0002]

2. Description of the Related Art When measuring a DC voltage or a DC current with a conventional analog tester having a function of measuring a voltage value, a current value and a resistance value, the polarity of a tester's input terminal is measured or measured. Unless the connection was made according to the polarity of the measurement current, the indicator of the tester oscillated in the opposite direction and the measurement was impossible.

Further, when measuring AC or DC voltage and current, it is necessary to switch the range of the tester to AC or DC for each measurement.

[0004]

In the conventional analog tester as described above, when measuring a direct current voltage or a direct current, the polarity of the measured voltage or the measured current and the polarity of the tester must always be confirmed. There is a problem that the operation is extremely troublesome because the measurement is required, and if the measured voltage or measured current is of unknown polarity, the indicator is swung in the opposite direction and the tester is destroyed. was there.

When measuring an AC or DC voltage and current, it is necessary to check in advance whether the measurement point of the circuit to be measured is AC or DC, and then switch the range of the tester for measurement. In addition, when AC or DC is unknown, there is a problem that measurement becomes impossible.

The present invention has been made in order to solve such a problem. Even when the DC polarity of the circuit under test is unknown, the polarity is automatically identified and displayed without confirming the polarity. An object of the present invention is to obtain an analog tester capable of always pointing the meter in the positive direction and automatically discriminating and displaying the alternating current of the circuit to be measured to indicate the meter always in the positive direction.

[0007]

An analog tester according to the present invention comprises a buffer and a resistor connected to the output side of the buffer, and supplies an electric current according to a measurement signal input via a range switching circuit. A current output circuit for outputting, an inverting amplifier for inverting the polarity of the signal due to the current and outputting the inverted signal, and a first anode connected to the inverting input terminal of the inverting amplifier.
A diode, a second diode having a cathode connected to the inverting input terminal, a third diode having an anode connected to the output terminal of the inverting amplifier and a cathode connected to the cathode of the first diode, and an anode of the second diode A bipolar response circuit including a fourth diode having an anode connected to the output terminal and a cathode connected to the output terminal, and one end connected to a connection point of the cathodes of the first and third diodes, and the bipolar response circuit of the second and fourth diodes. The other end is connected to the connection point of the anode, and it has an indicator that indicates the measured value based on the input of the signal from the bipolar response circuit, and a reactor wave circuit that removes the AC component of the output signal of the inverting amplifier. However, the display unit is turned on when the signal from the reactor wave circuit is the measured negative DC signal.

[0008]

In the present invention, when the signal to be measured is an alternating current, the positive signal component flows to the first diode, and the negative signal component is inverted by the inverting amplifier and flows to the second diode. Therefore, the AC measured signal is full-wave rectified and output to the indicator. At this time, the display unit remains unlit because the inverted signal is removed by the reactor wave circuit. When the signal to be measured is a positive direct current, the signal is output to the indicator via the first diode, and also the polarity is converted by the inverting amplifier and output to the reactor wave circuit. In this case, since the display portion has a negative polarity, it remains unlit. When the signal under measurement is a negative direct current, it is inverted to a positive polarity by the inverting amplifier and is output to the indicator via the second diode. At this time, the display unit lights up by inputting the signal of the positive pole, and indicates that the signal under measurement is the negative direct current.

[0009]

1 and 2 are circuit diagrams of an embodiment of the present invention, and FIG. 3 is an external view of FIGS. In the figure, 1 is a measurement input terminal coupled to a measurement terminal for measuring the voltage, current and resistance of the circuit under test, and 2 is a DC voltage range, an AC voltage range, a DC before measuring the circuit under test. A function switch 3 for switching and setting each of a current range, an alternating current range and a resistance range is a constant voltage source for applying a constant voltage to the circuit to be measured by the resistance range set by the function switch 2.

Reference numeral 4 denotes a range switching circuit provided with attenuation circuits for measuring DC current, DC voltage, AC current, AC voltage, and resistance. Reference numeral 5 denotes a constant voltage according to a signal output from the range switching circuit 4. A buffer (constant voltage source) for outputting, 6 is a resistor for obtaining a constant current with respect to the voltage from the buffer 5.

Reference numeral 7 is an inverting amplifier for inverting and outputting a signal by a constant current obtained by the buffer 5 and the resistor 6, and 8 is a first
A diode, 9 is a second diode, which detects a signal due to the constant current obtained by the buffer 5 and the resistor 6. Reference numeral 10 is a third diode, 11 is a fourth diode, and an inverting amplifier 7
Detect the output from. The detection diodes 8, 9, 10, 11 in FIG. 2 are connected in the direction opposite to that in FIG. Reference numeral 12 is an indicator for indicating a moving coil type needle based on the signals detected by the diodes 8, 9, 10 and 11.

Reference numeral 13 is a voltage dividing resistor for dividing the signals detected by the first and second diodes 8 and 9, and 14 is a reactor wave condenser for removing the AC component of the signal component via the resistor 13.
Reference numeral 5 is a switching transistor which is turned on when measuring the negative DC current and DC voltage, and 16 is a current limiting resistor for lighting the LED 17.

The analog tester of the present invention is constructed as described above. FIG. 4 is a timing chart showing waveforms at various points during measurement of DC current or DC voltage in the embodiment of FIG. 1, and FIG. 3 is a timing chart showing waveforms at various points when measuring an alternating current or an alternating voltage in the embodiment of FIG. 1, and the operation will be described.

First, referring to FIGS. 1 and 4, when measuring a DC current or a DC voltage (when the measurement point of the circuit to be measured has a positive polarity of the DC current or DC voltage), the function switch 2 is set to the DC current range, respectively. Alternatively, the setting is performed by switching to the DC voltage range, and the measurement terminal is connected to the circuit under measurement without considering the polarity of the circuit under measurement. Then, the DC current or DC voltage signal (positive signal) seen at the point a via the range switching circuit 4, the buffer 5, and the resistor 6 is input to the inverting input terminal of the inverting amplifier 7 and the anode of the first diode 8 and It is input to the cathode of the second diode 9, respectively. The signal input to the inverting amplifier 7 is an inverted DC current or DC voltage signal as shown at point b.

Further, the positive polarity signal input to the anode of the first diode 8 is a direct current signal of positive polarity or a direct current voltage signal of positive polarity as indicated by point c in the forward direction of the first diode 8. Closed loop through 12 and indicator 12
Indicates the needle in the forward direction by a value corresponding to the signal.

On the other hand, the DC current or DC voltage signal (waveform at point b) inverted by the inverting amplifier 7 is input to the base of the switching transistor 15 via the resistor 13 (waveform at point d), and the switching transistor is turned on. 15 is cut off. Therefore, the LED 17 that is turned on when the direct current or the DC voltage has a negative polarity is not turned on.

Next, in FIG. 1 and FIG. 4 (b), when measuring the direct current or the direct voltage (when the measuring point of the circuit under test has the negative direct current or direct voltage), Similarly, the function switch 2 is set by switching to the DC current range or the DC voltage range, and the measurement terminal is connected to the circuit under measurement without considering the polarity of the circuit under measurement. Then, the DC current or DC voltage signal (negative signal) seen at the point a via the range switching circuit 4, the buffer 5 and the resistor 6 is applied to the inverting input terminal of the inverting amplifier and the anode and the first diode 8 of the first diode 8. It is input to the cathodes of the two diodes 9, respectively. Then, the negative-polarity signal input to the inverting amplifier 7 is the inverted DC current or DC voltage signal as seen at the point b.

The negative signal inputted to the cathode of the second diode 9 is c due to the forward direction of the second diode 9.
As can be seen from the points, a positive polarity DC current or DC voltage signal is closed loop through the indicator 12, and the indicator 12 directs the needle in the forward direction by a value corresponding to the signal.

On the other hand, the DC current or DC voltage signal (waveform at point b) inverted by the inverting amplifier 7 is input to the base of the switching transistor 15 via the resistor 13 (waveform at point d), and the switching transistor is turned on. 15 turns on. Therefore, the LED 17 that is turned on when the DC current or DC voltage has a negative polarity is turned on.

Further, in FIG. 1 and FIG. 5, when measuring an alternating current or an alternating voltage, the function switch 2 is used.
Are switched to the AC current range or the AC voltage range, respectively, and the measurement terminals are connected to the circuit to be measured without considering the polarity of the circuit to be measured. Then, the signal of the alternating current or alternating voltage seen at the point a via the range switching circuit 4, the buffer 5 and the resistor 6 is applied to the inverting input terminal of the inverting amplifier, to the anode of the first diode 8 and to the cathode of the second diode 9. Each is entered. The alternating current or alternating voltage signal input to the inverting amplifier 7 is the inverted alternating current or alternating voltage signal output at point b.

The alternating current or alternating voltage signal inverted by the inverting amplifier 7 is detected by the third diode 10, and the alternating current or alternating voltage signal is detected by the first diode 8 at point c. As can be seen, the full-wave rectified signal is closed-loop through the indicator 12 and directs the needle in the positive direction by its effective value.

On the other hand, the AC current or AC voltage signal (waveform at point b) inverted by the inverting amplifier 7 is subjected to the reactor wave (waveform at point d) by the reactor wave capacitor 14 via the resistor 13 to be a switching transistor. The fifteen bases are cut off. Therefore, the LED 17 that is turned on when the direct current or the DC voltage has a negative polarity is not turned on.

The diodes 8, 9, 10, 1 shown in FIG.
In the embodiment of FIG. 2 in which 1's are connected in opposite directions, the same operation as above is performed only by reversing the direction of the current flowing through the indicator 12.

As described above, even if the polarity of the voltage or current of the circuit under test is unknown, the polarity is not considered and the negative polarity is automatically discriminated and displayed, and the indicator is always in the positive direction. Can be instructed and measured.

FIG. 6 is a circuit diagram of another embodiment of the present invention, FIG.
Is an external view of FIG. 6, 1, 3, 5-11, 13-16
Is the same as above. In the figure, 2A is a function switch which is set by switching to an AC / DC voltage range, an AC / DC current range, and a resistance range before measuring the circuit under test. 4A is AC / DC voltage,
A range switching circuit provided with attenuation circuits for measuring AC / DC current and resistance, 14A cuts the DC component of the signals detected by the first diode 8 and the second diode 9, and passes the AC component. Coupling capacitor, 1
7A is L that lights up when the AC component is measured in the circuit under measurement
It is ED.

An analog tester according to another embodiment of the present invention is constructed as described above, and FIG. 8 shows the waveform of each point when measuring the DC current or DC voltage in the embodiment of FIG. FIG. 9 is a timing chart shown, and FIG. 9 is a timing chart showing the waveform of each point when measuring the alternating current or alternating voltage in the embodiment of FIG. 6, and the operation will be described.

First, in FIGS. 6 and 8 (a), when the measurement point of the circuit to be measured is a positive DC current or DC voltage, the waveforms at points a, b and c in FIG. 1 are the same. (See FIG. 4a) becomes a closed loop via the indicator 12,
In the forward direction. On the other hand, at point d, the coupling capacitor 14A cuts off the direct current component and the base of the switching transistor 15 is cut off.
D17A becomes unlit.

Next, in FIGS. 6 and 8B, when the measurement point of the circuit to be measured is a DC current or DC voltage of negative polarity, the waveforms at points a, b and c in FIG. In the same manner (see FIG. 4b), the closed loop is performed via the indicating form 12,
In the forward direction. On the other hand, at point d, the coupling capacitor 14A cuts off the direct current component and the base of the switching transistor 15 is cut off.
D17A becomes unlit.

Further, in FIG. 6 and FIG. 9, when the measurement of the circuit under test is an alternating current or an alternating voltage, a of FIG.
The waveforms at points b and c are the same (see Fig. 5) and indicate
And the indicating form 12 is directed in the forward direction.
On the other hand, at point d, the AC component is passed by the coupling capacitor 14A, and the switching transistor 1
The base of No. 5 is biased and the LED 17A lights up. Even if the diodes 8, 9, 10, and 11 in FIG. 6 are connected in the opposite directions, the same operation as described above is possible only by reversing the direction of the current flowing through the indicator 12.

Thus, even if the AC or DC of the circuit to be measured is unknown, the AC component is automatically discriminated and displayed without consideration, and the indicator is always pointed in the forward direction for measurement. be able to.

[0031]

As described above, according to the present invention, the component of the signal under measurement is automatically discriminated and displayed, and the component of the signal under measurement is rectified so that the indicator is always directed in the forward direction. Therefore, the measurement can be performed without considering the polarity of the DC current or the DC voltage of the signal under measurement, and the destruction of the measuring device can be prevented. Further, the measurement can be performed without considering the direct current or the alternating current of the signal under measurement.

Further, since a current output circuit consisting of a buffer and a resistor is provided in the preceding stage of the bipolar response circuit so that a constant current corresponding to the measurement signal is applied to the indicator, the influence of the temperature change of the movable part is exerted. It is also possible to obtain the effect that the measurement error is unlikely to occur without being affected.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an embodiment of the present invention.

FIG. 2 is a circuit diagram of an embodiment of the present invention.

FIG. 3 is an external view of FIGS. 1 and 2.

FIG. 4 is a timing chart showing waveforms at various points when measuring a direct current or a direct voltage in the embodiment of FIG.

5 is a timing chart showing waveforms at various points when measuring an alternating current or an alternating voltage in the embodiment of FIG.

FIG. 6 is a circuit diagram of another embodiment of the present invention.

FIG. 7 is an external view of FIG.

8 is a timing chart showing waveforms at various points when measuring a DC current or a DC voltage in the embodiment of FIG.

9 is a timing chart showing waveforms at various points when measuring an alternating current or an alternating voltage in the embodiment of FIG.

[Explanation of symbols]

 1 Input terminal for measurement 2 Function switch 3 Constant voltage source 4 Range switching circuit 5 Buffer 6 Resistance 7 Inversion amplifier 8 First diode 9 Second diode 10 Third diode 11 Fourth diode 12 Indicator 13 Voltage dividing resistor 14 For furnace wave Capacitor 15 Switching transistor 16 Current limiting resistor 17 LED

Claims (3)

[Claims] 1. A current output circuit comprising a buffer and a resistor connected to the output side of the buffer, which outputs a current in accordance with a measurement signal input through a range switching circuit, and a polarity of the signal due to the current. An inverting amplifier that inverts and outputs, a first diode whose anode is connected to the inverting input terminal of the inverting amplifier, a second diode whose cathode is connected to the inverting input terminal, and an anode which is connected to the output terminal of the inverting amplifier A bipolar response circuit comprising a third diode having a cathode connected to the cathode of the first diode, and a fourth diode having an anode connected to the anode of the second diode and a cathode connected to the output terminal; One end is connected to the connection point of the cathodes of the first and third diodes, and the other end is connected to the connection point of the anodes of the second and fourth diodes. An indicator that indicates a measurement value based on the input of a signal from the bipolar response circuit, and a reactor wave circuit that removes an AC component from the output signal of the inverting amplifier. An analog tester, which is turned on when the signal is the measured negative DC signal. 2. The display unit has a reactor wave circuit for removing a DC component of the output signal of the inverting amplifier, and is turned on when the signal from the reactor wave circuit is the measured AC signal. The analog tester according to claim 1, wherein: 3. The analog tester according to claim 1, wherein the first, second, third and fourth diodes are connected so that their characteristics have opposite characteristics.