CN214474613U - Test device for differential mode and common mode rejection ratio of PLC analog input module - Google Patents

Abstract

The utility model discloses a PLC analog input module differential mode and common mode rejection ratio's testing arrangement relates to the industrial automation field. The test device for the differential mode and common mode rejection ratio of the PLC analog input module is exquisite in structure, good in test effect and stable in test result. The device comprises an analog input signal source, an analog interference source, a wiring terminal, a PLC analog input module, a CPU module, an upper computer and a power supply module; the analog input signal source and the analog interference source are both connected with a PLC analog input module through wiring terminals, the analog input module is connected with a CPU module, and the CPU module is connected with the upper computer; and supplying power to the PLC analog input module and the CPU module through the power supply module. And a novel analog interference source circuit is adopted, so that the precision is high and the load driving capability is strong. The test efficiency of the differential mode and common mode rejection ratio of the PLC analog input module is improved.

Description

Test device for differential mode and common mode rejection ratio of PLC analog input module

Technical Field

The utility model relates to an industrial automation field especially relates to a PLC analog input module differential mode and common mode rejection ratio's testing arrangement.

Background

At present, in the field application of industrial automation, a Programmable Logic Controller (PLC) is more and more favored by industrial field automation engineers due to its strong functions, simple graphical programming language, rich communication interfaces and wide application field.

At present, the PLC of an industrial automation field is mainly composed of a power supply module, a CPU module, a digital quantity module, an analog quantity module and the like; in industrial automation field application, differential mode interference exists between signal lines and common mode interference exists between the signal lines and the ground due to complexity of field signal wiring in an input signal acquisition process of an analog input module, and conventional testing has higher requirements on skills of testing equipment and testing personnel and lower testing efficiency.

SUMMERY OF THE UTILITY MODEL

The utility model discloses to above problem, provided a PLC analog quantity input module differential mode and common mode rejection ratio's testing arrangement that the structure is exquisite, the test effect is good, the test result is stable.

The technical scheme of the utility model is that: the device comprises an analog input signal source, an analog interference source, a wiring terminal, a PLC analog input module, a CPU module, an upper computer and a power supply module;

the analog input signal source and the analog interference source are both connected with a PLC analog input module through wiring terminals, the analog input module is connected with a CPU module, and the CPU module is connected with the upper computer; and supplying power to the PLC analog input module and the CPU module through the power supply module.

And the wiring terminal is connected with an input channel of the PLC analog input module.

The analog input module is connected with the CPU module through an internal bus.

And the CPU module transmits the data to the upper computer through the Ethernet.

The analog interference source is generated by an interference source analog circuit, and the interference source analog circuit comprises a diode D1, an isolation DCDC power supply, a DAC (digital-to-analog converter), an MCU (microprogrammed control unit), an NPN triode D3, a resistor R1 and a protection diode D2;

external input 24VDC power passes through diode D1, keeps apart the DCDC power connection DAC digital-to-analog converter in proper order, MCU connects DAC digital-to-analog converter to control DAC digital-to-analog converter output voltage signal through MCU, the NPN triode D3's that DAC digital-to-analog converter still connects collector, base and resistance R1, the positive pole of protection diode D2 is connected simultaneously to NPN triode D3's projecting pole and resistance R1, protection diode D2's negative pole is connected binding post.

The utility model discloses following beneficial effect has: firstly, a novel analog interference source circuit is adopted, the precision is high, and the load driving capability is strong. And secondly, the test efficiency of the differential mode and common mode rejection ratio of the PLC analog input module is improved. And thirdly, the test cost of the differential mode and common mode rejection ratio of the PLC analog input module is reduced. Fourthly, the utility model discloses reduced the requirement to tester skill.

Compared with the prior art the utility model discloses a neotype simulation interference source circuit, the precision is high, load driving force is strong, does not need extra test equipment, need not understand the module principle and just can realize differential mode and common mode rejection ratio test through the PLC module, and test method operation is simpler, the cost is lower, work efficiency is higher. The utility model is suitable for a PLC analog input module differential mode and common mode rejection ratio test.

Drawings

FIG. 1 is a schematic structural diagram of the present application,

fig. 2 is a schematic structural diagram of an interference source simulation circuit in the present application.

Detailed Description

In order to clearly explain the technical features of the present patent, the following detailed description of the present patent is provided in conjunction with the accompanying drawings.

The utility model is shown in fig. 1-2, and comprises an analog input signal source, an analog interference source, a wiring terminal, a PLC analog input module, a CPU module, an upper computer and a power supply module;

the analog input signal source and the analog interference source are both connected with a PLC analog input module through wiring terminals, the analog input module is connected with a CPU module, and the CPU module is connected with the upper computer; and supplying power to the PLC analog input module and the CPU module through the power supply module.

The analog input signal source mainly utilizes a PLC analog output module to output a normal voltage signal in an analog mode; the analog interference source mainly utilizes an analog interference source circuit to simulate and output a sine wave interference signal with 50Hz and Ea peak value.

During testing, firstly, the analog interference source adopts a 16-bit DAC to ensure the accuracy of output voltage, and the output interference signal is ensured not to be interfered by the outside through an isolation DCDC power supply circuit and a triode drive circuit; and then, the PLC analog input module converts the normal voltage signal and the interfered voltage signal into digital signals, transmits the CPU module through an internal bus, and sends data to an upper computer through the Ethernet, and then obtains the differential mode and common mode rejection ratio of the PLC analog input module through calculation.

In the above, the analog interference source is connected with the input channel of the PLC analog input module, and after the interference source is loaded, the jitter range of the PLC analog input module is checked, and the maximum value and the minimum value of jitter are taken, Vac = maximum value-minimum value.

And the wiring terminal is connected with an input channel of the PLC analog input module.

The analog input module is connected with the CPU module through an internal bus.

And the CPU module transmits the data to the upper computer through the Ethernet.

The analog interference source is generated by an interference source analog circuit, and the interference source analog circuit comprises a diode D1, an isolation DCDC power supply, a DAC (digital-to-analog converter), an MCU (microprogrammed control unit), an NPN triode D3, a resistor R1 and a protection diode D2;

external input 24VDC power passes through diode D1, keeps apart the DCDC power connection DAC digital-to-analog converter in proper order, MCU connects DAC digital-to-analog converter to control DAC digital-to-analog converter output voltage signal through MCU, the NPN triode D3's that DAC digital-to-analog converter still connects collector, base and resistance R1, the positive pole of protection diode D2 is connected simultaneously to NPN triode D3's projecting pole and resistance R1, protection diode D2's negative pole is connected binding post.

Therefore, an external input 24VDC power supply provides an isolation power supply for the DAC through the D1 protection diode and the isolation DCDC power supply to ensure that the circuit is not interfered by the outside, the MCU controls the 16-bit DAC to output a voltage signal in a bus mode, the output voltage signal is output through the D3 NPN triode and the resistor R1, the output efficiency can be improved by adopting the output of the triode, the heat of the DAC is reduced, the output voltage is output through the D3 and then the protection diode D2, and the D2 diode is mainly used for improving the anti-interference performance of the output.

The power supply of the analog interference source circuit adopts an isolation DCDC circuit to ensure that an output signal is not interfered by the outside; the analog interference source circuit adopts a high-power NPN triode to drive different loads, so that the output efficiency is improved, the heat of the DAC is reduced, and the analog interference source is ensured to be suitable for different test occasions.

The present invention has many specific implementation ways, and the above description is only the preferred embodiment of the present invention, it should be noted that, for those skilled in the art, a plurality of improvements can be made without departing from the principles of the present invention, and these improvements should also be regarded as the protection scope of the present invention.

Claims (5)

1. A test device for a differential mode and a common mode rejection ratio of a PLC analog input module is characterized by comprising an analog input signal source, an analog interference source, a wiring terminal, a PLC analog input module, a CPU module, an upper computer and a power supply module;

the analog input signal source and the analog interference source are both connected with a PLC analog input module through wiring terminals, the PLC analog input module is connected with a CPU module, and the CPU module is connected with the upper computer; and supplying power to the PLC analog input module and the CPU module through the power supply module.

2. The device for testing the differential mode and common mode rejection ratio of the PLC analog input module as claimed in claim 1, wherein said connection terminal is connected to the input channel of the PLC analog input module.

3. The device for testing the differential mode and common mode rejection ratio of a PLC analog input module as claimed in claim 1, wherein said analog input module is connected to the CPU module through an internal bus.

4. The device for testing the differential mode and common mode rejection ratio of the PLC analog input module as claimed in claim 1, wherein the CPU module sends data to the upper computer through Ethernet.

5. The device for testing the differential-mode and common-mode rejection ratio of the PLC analog input module of claim 1, wherein the analog interference source is generated by an interference source analog circuit, and the interference source analog circuit comprises a diode D1, an isolated DCDC power supply, a DAC digital-to-analog converter, an MCU, an NPN triode D3, a resistor R1 and a protection diode D2;

external input 24VDC power passes through diode D1, keeps apart the DCDC power connection DAC digital-to-analog converter in proper order, MCU connects DAC digital-to-analog converter to control DAC digital-to-analog converter output voltage signal through MCU, the NPN triode D3's that DAC digital-to-analog converter still connects collector, base and resistance R1, the positive pole of protection diode D2 is connected simultaneously to NPN triode D3's projecting pole and resistance R1, protection diode D2's negative pole is connected binding post.

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