Anti-misoperation type voltage and resistance dual-purpose measuring meter

Abstract

The utility model relates to the technical field of measuring instruments, in particular to an anti-misoperation type voltage and resistance dual-purpose measuring meter. The dual-purpose measuring meter is provided with test pen holes, the test pen holes comprise a red pen hole and a black pen hole, and the dual-purpose measuring meter further comprises a signal switching circuit composed of two double-pole double-throw relays, a current measuring circuit, a voltage measuring circuit, a display circuit, a key circuit, a power supply circuit, a startup and shutdown circuit and a microprocessor. According to the utility model, two functions of the intrinsic safety technology can be realized, i.e., a protective function that an operator does not cause an accident of a power grid, equipment or human injury even if the operator operates mistakenly, and when the measuring meter has a technical fault or a function failure, the safety of the measuring meter is ensured, and the safety of the measuring meter is ensured. And the safety protection performance can be automatically carried out, so that further occurrence of power grid, equipment or human injury accidents is avoided.

Description

Technical Field

[0001] The utility model relates to the technical field of circuit measuring instruments, in particular to an anti-misoperation type voltage and resistance dual-purpose measuring instrument. Background Technique

[0002] Voltage test and resistance test are two functions most frequently used in debugging among many functions of current measuring instruments. However, the input impedance of the resistance range of existing measuring instruments is generally low. If there is a slight improper operation, such as when the measuring instrument is rotated to the resistance range to measure the resistance between two wires, and if the measured wire is energized at this time, due to the low input impedance of the resistance range of the measuring instrument, it is easy to cause a short-circuit phenomenon of the measured wire, which may lead to the burning of the instrument, the short circuit of the measured line, the tripping of the leakage switch, equipment warnings, etc. Maintenance personnel usually need to use the measuring instrument to check and measure signal wires. If the resistance range of the measuring instrument is used to measure the energized signal wire, some professional equipment in the substation control room, such as relay protection devices, monitoring instruments, etc. During the normal operation of the power system, some signals will be monitored for abnormalities. At this time, the voltage of the signal wire will be pulled down, which may cause warnings on the monitoring instrument at least, and may cause some protection actions on the instrument, resulting in a high-voltage power outage at worst. Content of the Utility Model

[0003] The purpose of the utility model is to provide an anti-misoperation type voltage and resistance dual-purpose measuring instrument to solve the disadvantages existing in the prior art.

[0004] To achieve the above purpose, the utility model provides the following technical solution: an anti-misoperation type voltage and resistance dual-purpose measuring instrument, the measuring instrument is provided with test pen holes, the test pen holes include a red pen hole and a black pen hole, and the dual-purpose measuring instrument further includes a signal switching circuit, a current measuring circuit, a voltage measuring circuit, a display circuit, a key circuit, a power supply circuit, a switching-on and -off circuit and a microprocessor composed of two double-pole double-throw relays. One end of the signal switching circuit is respectively connected to the red pen hole and the black pen hole for testing, and the other end is respectively connected to the current measuring circuit and the voltage measuring circuit for switching between the current measuring circuit and the voltage measuring circuit. The signal switching circuit, the current measuring circuit, the voltage measuring circuit, the display circuit, the key circuit, the power supply circuit and the switching-on and -off circuit are all electrically connected to the microprocessor.

[0005] Preferably, the two double-pole double-throw relays include a first relay and a second relay. The two common terminals of the first relay are respectively connected to the red test pen hole and the black test pen hole. The two normally closed contacts of the first relay are respectively connected to the two common terminals of the second relay. One normally open contact of the first relay is grounded, and the other normally open contact is connected to the voltage detection circuit. The two normally closed contacts of the second relay are suspended. One normally open contact of the second relay is connected to the current detection circuit, and the other normally open contact is connected to the voltage detection circuit.

[0006] Preferably, the model of the microprocessor is STM32F103RCT6.

[0007] Preferably, the current measurement circuit includes a sampling circuit and a first amplification circuit.

[0008] Preferably, the voltage measurement circuit includes a voltage division circuit and a second amplification circuit.

[0009] Preferably, the power on / off circuit includes 1 MOS transistor, 2 diodes, 1 triode, 4 resistors, and 1 touch button. Diode D4 is connected to the PC7 port of the microprocessor, and diode D3 is connected to the PC6 port of the microprocessor.

[0010] Beneficial effects:

[0011] The present utility model is provided with a switching circuit, a voltage measurement circuit with a high resistance value, and a current measurement circuit. When in use, the voltage of the object to be measured is measured first. Since the internal resistance of the voltage measurement circuit is relatively high, even when measuring the voltage of a live signal line in the secondary circuit, it will not cause the burning of the instrument, the short circuit of the measured line, the tripping of the leakage switch, or the warning of the equipment. Therefore, it eliminates the abnormal situations such as the warning of the monitoring instrument caused by mistakenly measuring the live signal line and relay protection devices, monitoring instruments and other equipment with a resistance file during the measurement of the secondary circuit by the existing measurement meter, or the occurrence of abnormal situations such as high-voltage power outage caused by some protection actions of the instrument. Description of the drawings

[0012] Figure 1 The structural block diagram of the present utility model;

[0013] Figure 2 The overall circuit diagram of the present utility model;

[0014] Figure 3 The signal switching circuit diagram of the present utility model;

[0015] Figure 4 The current measurement circuit diagram of the present utility model;

[0016] Figure 5 The voltage measurement circuit diagram of the present utility model;

[0017] Figure 6 The button circuit diagram of the present utility model;

[0018] Figure 7 The power on / off circuit diagram of the present utility model; Detailed implementation manners

[0019] Next, the technical solutions in an embodiment of the present utility model will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention.

[0020] Please refer to Figure 1-7 : An anti-misoperation type voltage and resistance dual-use measuring instrument. The measuring instrument is provided with test pen holes, and the test pen holes include a red pen hole and a black pen hole. The dual-use measuring instrument also includes a signal switching circuit composed of two double-pole double-throw relays, a current measuring circuit, a voltage measuring circuit, a display circuit, a key circuit, a power supply circuit, a power-on and power-off circuit, and a microprocessor. One end of the signal switching circuit is respectively connected to the red pen hole and the black pen hole for testing, and the other end is respectively connected to the current measuring circuit and the voltage measuring circuit for switching between the current measuring circuit and the voltage measuring circuit. The signal switching circuit, the current measuring circuit, the voltage measuring circuit, the display circuit, the key circuit, the power supply circuit, and the power-on and power-off circuit are all electrically connected to the microprocessor.

[0021] The two common terminals of the first relay are respectively connected to the red test pen hole and the black test pen hole. The two normally closed contacts of the first relay are respectively connected to the two common terminals of the second relay. One normally open contact of the first relay is grounded, and the other normally open contact is connected to the voltage detection circuit. The two normally closed contacts of the second relay are left floating. One normally open contact of the second relay is connected to the current detection circuit, and the other normally open contact is connected to the voltage detection circuit.

[0022] The model of the microprocessor is STM32F103RCT6. Selecting this microprocessor has the advantages of high operating frequency, built-in ADC, large-capacity memory, etc., and can perform high-speed operations, and can measure and display measurement results in real time.

[0023] The current measuring circuit includes a sampling circuit and a first amplifying circuit. Among them, the sampling circuit is used to convert the current signal into a voltage signal, and the first amplifying circuit is used to amplify the voltage signal to a suitable value.

[0024] The voltage measuring circuit includes a voltage dividing circuit and a second amplifying circuit. Among them, the voltage dividing circuit is used to reduce the signal, and the second amplifying circuit is used to amplify the reduced signal to a suitable value.

[0025] The power-on and power-off circuit includes 1 MOS tube, 2 diodes, 1 triode, 4 resistors, and 1 touch key. The diode D4 is connected to the PC7 port of the microprocessor, and the diode D3 is connected to the PC6 port of the microprocessor. When the touch switch is pressed, the key conducts R41 and R42 to divide the battery voltage and then give it to the control pin of the triode, and the triode conducts. The control pin level of the MOS tube is low, and the MOS tube conducts to supply power to the entire circuit board. The microprocessor passes the circuit to set the PC6 to a high level, which is transmitted to the control pin of the triode through the diode D3. The PC6 signal of the microprocessor can replace the level signal when the key is pressed. At this time, the instrument is powered on, and automatic power-off after 30 minutes of inactivity can be achieved through software programming.

[0026] Working principle:

[0027] When the measuring instrument is powered on, both the first relay and the second relay are in the normally open state.

[0028] Neither the black hole nor the red hole is connected to any module of the instrument.

[0029] At this time, the insulation performance of the measuring instrument is equivalent to that of the relay.

[0030] When the resistance test key of the measuring instrument is pressed, the first relay connects the object to be measured and the voltage measurement circuit. The voltage measurement circuit measures the voltage measurement value of the object to be measured, and the microprocessor compares the voltage measurement value with the safety voltage value (such as 5 volts). If the voltage measurement value is greater than the safety voltage value, it means that the object to be measured is energized, the liquid crystal display gives a prompt and the second relay does not act, and the second relay remains in the normally open state, and the current measurement circuit is not conducting, thus avoiding short circuit or voltage signal being pulled down.

[0031] If the voltage measurement value is not greater than the safety voltage value, it means that the object to be measured has no voltage and can be safely measured. The first relay disconnects the object to be measured and the voltage measurement circuit. At the same time, it connects the object to be measured and the second relay, and the second relay connects the first relay and the current measurement circuit. The current measurement circuit measures the current measurement value of the object to be measured, and the microprocessor calculates the ratio of the measured voltage and the measured current to obtain the resistance value of the object to be measured.

[0032] The above are only the embodiments of the present invention, and do not limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made by using the content of the specification and drawings of the present invention, or directly or indirectly applied in other related technical fields, are equally included in the patent protection scope of the present invention.

Claims

1. A voltage and resistance dual-use measuring instrument with anti-misoperation function, the measuring instrument is provided with test pen holes, and the test pen holes include a red pen hole and a black pen hole, and are characterized in that: The dual-purpose measuring instrument further includes a signal switching circuit composed of two double-pole double-throw relays, a current measurement circuit, a voltage measurement circuit, a display circuit, a key circuit, a power supply circuit, a power-on / off circuit, and a microprocessor. One end of the signal switching circuit is respectively connected to the red pen hole and the black pen hole for testing, and the other end is respectively connected to the current measurement circuit and the voltage measurement circuit, and is used for switching between the current measurement circuit and the voltage measurement circuit. The signal switching circuit, the current measurement circuit, the voltage measurement circuit, the display circuit, the key circuit, the power supply circuit, and the power-on / off circuit are all electrically connected to the microprocessor.

2. The dual-purpose voltage and resistance measuring instrument with anti-misoperation function according to claim 1, wherein: The two double-pole double-throw relays include a first relay and a second relay. The two common terminals of the first relay are respectively connected to the red test lead hole and the black test lead hole. The two normally closed contacts of the first relay are respectively connected to the two common terminals of the second relay. One normally open contact of the first relay is grounded, and the other normally open contact is connected to the voltage detection circuit. The two normally closed contacts of the second relay are floating. One normally open contact of the second relay is connected to the current detection circuit, and the other normally open contact is connected to the voltage detection circuit.

3. A voltage and resistance dual-use measuring instrument with anti-misoperation function according to claim 1, characterized in that: The model of the microprocessor is STM32F103RCT6.

4. The dual-purpose voltage and resistance measuring instrument with anti-misoperation according to claim 1, characterized in that: The current measurement circuit includes a sampling circuit and a first amplifier circuit.

5. The dual-purpose voltage and resistance measuring instrument with anti-misoperation according to claim 1, characterized in that: The voltage measurement circuit includes a voltage division circuit and a second amplifier circuit.

6. The voltage and resistance dual-use measuring instrument with anti-misoperation according to claim 1, characterized in that: The power-on / off circuit includes 1 MOS transistor, 2 diodes, 1 triode, 4 resistors, and 1 momentary push button. Diode D4 is connected to the PC7 port of the microprocessor, and diode D3 is connected to the PC6 port of the microprocessor.

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