A DC instrument testing tool and method

Abstract

The present invention relates to the field of electric energy meter detection equipment, and in particular to a test fixture for a direct current meter, comprising a direct current meter, a switching device, a standard source, a test device and at least two shunts of different specifications; the direct current meter, the standard source and the switching device are respectively connected to the test device, the at least two shunts of different specifications are respectively connected to the switching device, and the at least two shunts of different specifications are connected in series to the standard source; the test device switches shunts of different specifications through the switching device, thereby reducing the time wasted by production test personnel due to manual replacement of shunts, and further improving work efficiency; the present invention also discloses a test method based on the above-mentioned test fixture, which sequentially switches shunt channels of different specifications, making the test process of the direct current meter test fixture more convenient and more automated.

Description

Technical Field

[0001] The invention relates to the field of electric energy meter detection equipment, and in particular to a testing tool and method for a direct current meter. Background Art

[0002] In the prior art, since DC meters are equipped with shunts of different ratios according to different load currents in field applications, in order to facilitate use, DC meters must be compatible with the access requirements of shunts of different ratios. Therefore, the production process of DC meters needs to be calibrated with each shunt of different ratios, and each calibration of different shunts requires manual wiring and replacement, resulting in a great deal of time being wasted in replacing shunts during the production process, which in turn causes low production efficiency of DC meters. Summary of the invention

[0003] The purpose of the present invention is to solve at least one of the technical problems existing in the prior art and to provide a test fixture for a DC meter capable of calibrating at least two ranges of the DC meter at the same time.

[0004] The present invention is achieved through the following technical solutions:

[0005] According to a first aspect of the present invention, there is provided a test fixture for a DC meter, comprising a DC meter, a switching device, a standard source, a test device and at least two shunts of different specifications; the DC meter, the standard source and the switching device are respectively connected to the test device, the at least two shunts of different specifications are respectively connected to the switching device, and the at least two shunts of different specifications are connected in series to the standard source.

[0006] Furthermore, the switching device includes at least two switch circuits, and output ends of the at least two switch circuits are connected in parallel.

[0007] Preferably, in the switching circuit, one end of the resistor R2 is connected to the output end of the test device, the other end of the resistor R2 is connected to the base of the NPN transistor Q1, the other end of the resistor R2 is simultaneously connected to one end of the resistor R1 and one end of the capacitor C1, the other end of the resistor R1 and the other end of the capacitor C1 are grounded, the collector of the NPN transistor Q1 is connected to the anode of the diode D1, the collector of the NPN transistor Q1 is simultaneously connected to the No. 8 terminal of the relay K1, the cathode of the diode D1 and the No. 7 terminal of the relay K1 are connected to the power supply, the No. 1 terminal and the No. 4 terminal of the relay K1 are connected to the shunt, the No. 2 terminal and the No. 5 terminal of the relay are connected to the input end of the test device, and the emitter of the NPN transistor Q1 is grounded.

[0008] Preferably, the testing tool of the present invention further comprises a computer display connected to the testing device.

[0009] Preferably, the DC meter and the standard source are connected to the test device via RS485 interfaces respectively, and the computer display is connected to the test device via RS232 interfaces.

[0010] According to a second aspect of the present invention, a testing method based on the above-mentioned testing fixture is provided, which specifically comprises the following steps: S1, the testing device controls the switching device to switch to the first shunt channel; S2, the testing device controls the DC meter to switch to the range with the same transformation ratio as the shunt; S3, the testing device controls the standard source to output a current signal to the shunt and output a voltage signal to the switching device; S4, the testing device collects the current and voltage signals of the switching device and transmits them to the DC meter; S5, the DC meter detects the current and voltage signals and sends the displayed current value and voltage value to the testing device; S6, the testing device compares the current value and voltage value measured by the DC meter with the current value and voltage value of the standard source. If the difference is greater than the error range, the testing device issues a calibration command to the DC meter until the difference between the current and voltage tested by the DC meter and the standard source is less than the error range; S7, the testing device issues a switch command to the switching device to switch to the next shunt channel, and repeats steps S2 to S6 until all shunts are calibrated; S8, the testing device sends the result of the successful calibration and the data record of each shunt to the computer display through the interface.

[0011] Furthermore, the error range of the above step S6 is 1% to 3%.

[0012] The beneficial effect is that the test fixture of the DC instrument of the present invention can access shunts of different specifications through a switching device, thereby realizing the function of calibrating multi-range DC instruments using the same test fixture, thereby improving the work efficiency of production testers.

[0013] The present invention also discloses a testing method based on the above-mentioned testing tool, which sequentially switches shunt channels of different specifications and sends control commands through the testing device, thereby realizing the automatic calibration function of the DC instrument testing tool. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The specific embodiments of the present invention are further described in detail below with reference to the accompanying drawings, wherein:

[0015] Figure 1 It is a structural schematic diagram of a preferred embodiment of the present invention;

[0016] Figure 2 FIG. 4 is a circuit diagram of a switching device according to a preferred embodiment of the present invention. DETAILED DESCRIPTION

[0017] This section will describe in detail the specific embodiments of the present invention. The preferred embodiments of the present invention are shown in the accompanying drawings. The purpose of the accompanying drawings is to supplement the description of the text part of the specification with graphics, so that people can intuitively and vividly understand each technical feature and the overall technical solution of the present invention, but it cannot be understood as a limitation on the scope of protection of the present invention.

[0018] In the description of the present invention, it should be understood that descriptions involving orientations, such as up, down, front, back, left, right, etc., and orientations or positional relationships indicated are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0019] In the description of the present invention, "several" means one or at least two, "at least two" means more than two, "greater than", "less than", "exceed", etc. are understood to exclude the number itself, and "above", "below", "within", etc. are understood to include the number itself. If there is a description of "first" or "second", it is only used for the purpose of distinguishing technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0020] In the description of the present invention, unless otherwise clearly defined, terms such as setting, installing, connecting, etc. should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in the present invention based on the specific content of the technical solution.

[0021] Reference Figure 1 A test fixture for a DC meter comprises a DC meter, a switching device, a standard source, a test device and at least two shunts of different specifications; the DC meter, the standard source and the switching device are respectively connected to the test device, the test device can control the standard source to output current or voltage signals, send control commands to control the switching device to switch shunts of different specifications, transmit current and voltage signals to the DC meter and receive current values ​​and voltage values ​​measured by the DC meter; at least two shunts of different specifications are respectively connected to the switching device, the shunt can input current signals into the test device through the switching device; the at least two shunts of different specifications are connected in series to the standard source, and the standard source outputs current signals to the shunt.

[0022] In this embodiment, the switching device includes at least two switch circuits, the output ends of the at least two switch circuits are connected in parallel, and the switch circuit can receive a control command from the measuring device to select a shunt of corresponding specifications to connect to the testing device.

[0023] Specifically, refer to Figure 2The switch circuit includes resistors R1, R2, an NPN transistor Q1, a diode D1, a capacitor C1, and a relay K1; one end of the resistor R2 is connected to the output end of the test device, and the end is used to receive the control signal of the test device, and the control signal is set to be high level valid, the other end of the resistor R2 is connected to the base of the NPN transistor Q1, the other end of the resistor R2 is simultaneously connected to one end of the resistor R1 and one end of the capacitor C1, the other end of the resistor R1 and the other end of the capacitor C1 are grounded, the collector of the NPN transistor Q1 is connected to the anode of the diode D1, the collector of the NPN transistor Q1 is simultaneously connected to the No. 8 terminal of the relay K1, the cathode of the diode D1 and the No. 7 terminal of the relay K1 are connected to the power supply, the No. 1 terminal and the No. 4 terminal of the relay K1 are connected to the shunt, the No. 2 terminal and the No. 5 terminal of the relay are connected to the input end of the test device, and the emitter of the NPN transistor Q1 is grounded.

[0024] The working principle of the switching circuit is: the test device outputs a high level to the base of the transistor Q1, the emitter is grounded as a low level, the collector and emitter of the transistor Q1 are turned on, so that the collector of the transistor Q1 is at a low level, the terminal 7 of the relay K1 is connected to the power supply, so there is voltage at both ends of the relay K1, the terminal 1 and the terminal 2 of the relay K1 are closed, and the terminal 4 and the terminal 5 are closed; since the other switching circuits do not receive the high-level control signal, the relays of the other switching circuits are in a disconnected state, and the output end of the switching circuit is successfully switched to the first shunt channel.

[0025] Preferably, the test fixture of the present invention further comprises a computer display connected to the test device, and the computer display is connected to the test device via an RS232 interface; the computer display is used to display the calibration results and the current and voltage values ​​of each shunt.

[0026] Preferably, the DC meter and the standard source are connected to the test device via RS485 interfaces respectively. The RS-485 interface uses differential signals for transmission. When there is noise interference, the difference between the two on the line can still be used for judgment, so that the transmitted data is not affected by noise.

[0027] According to a second aspect of the present invention, a testing method based on the above-mentioned testing tool is provided, which specifically comprises the following steps:

[0028] S1, the test device controls the switching device to switch to the first shunt channel; the test device sends a high level signal to one end of the resistor R1, and the relay K1 is turned on;

[0029] S2, the test device controls the DC meter to switch to the range with the same ratio as the shunt;

[0030] S3, the test device sends a control command through the RS485 interface to control the standard source to output a current signal to the shunt and output a voltage signal to the switching device;

[0031] S4, the test device collects the current and voltage signals of the switching device and transmits them to the DC instrument;

[0032] S5, the DC meter detects the current and voltage signals, and outputs the displayed current value and voltage value to the test device;

[0033] S6, the test device compares the current value and voltage value measured by the DC meter with the current value and voltage value of the standard source. If the difference is greater than the error range, the test device issues a calibration command to the DC meter until the difference between the current and voltage measured by the DC meter and the standard source is less than the error range, and the error range is 1% of the current value and voltage value of the standard source;

[0034] S7, the testing device sends a command to the switching device to switch to the next shunt channel, and repeats steps S2 to S6 until all shunts are calibrated;

[0035] S8, the test device sends the result of successful calibration and the data record of each shunt to the computer display through the interface.

[0036] The above embodiments are not limited to the technical solutions of the embodiments themselves, and the embodiments can be combined with each other to form new embodiments. The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Any modification or equivalent replacement that does not deviate from the spirit and scope of the present invention shall be included in the scope of the technical solutions of the present invention.

Claims

1. A testing method based on a testing tool, characterized in that: The test fixture comprises a DC meter, a switching device, a standard source, a test device and at least two shunts of different specifications; the DC meter, the standard source and the switching device are respectively connected to the test device, the at least two shunts of different specifications are respectively connected to the switching device, and the at least two shunts of different specifications are connected in series to the standard source. The method specifically comprises the following steps: S1, the test device controls the switching device to switch to the first shunt channel; S2, the test device controls the DC meter to switch to the range with the same ratio as the shunt; S3, the test device controls the standard source to output a current signal to the shunt, and the shunt outputs a voltage signal to the switching device, and records its voltage and current values; S4, the test device collects the voltage signal of the switching device and transmits it to the DC meter; S5, the DC meter detects the voltage signal and sends the displayed current value to the test device; S6, the test device compares the current value displayed by the DC meter with the current value of the standard source. If the difference is greater than the error range, the test device issues a calibration command to the DC meter until the difference between the current value displayed by the DC meter and the standard source is less than the error range. S7, the testing device sends a command to the switching device to switch to the next shunt channel, and repeats steps S2 to S6 until all shunts are calibrated; S8, the test device sends the result of successful calibration and the data record of each shunt to the computer display through the interface.

2. A test method based on a test fixture according to claim 1, characterized in that: The switching device includes the same number of switch circuits as the shunts.

3. A test method based on a test fixture according to claim 2, characterized in that: The output ends of each switch circuit are connected in parallel.

4. A test method based on a test fixture according to claim 1, characterized in that: Also included is a computer display connected to the testing device.

5. A test method based on a test fixture according to claim 3, characterized in that: The DC meter and the standard source are connected to the test device via RS485 interfaces respectively.

6. A test method based on a test fixture according to claim 1, characterized in that: The error range of step S6 is 1% to 3%.

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