The particle size counter is used for oil contamination detection, which can accurately measure the number of various specifications of particles in the oil and is an important component in oil contamination detection. The dynamic calibration test bench for oil contamination detection instrument is used to calibrate the particle size counter. Under constant pressure and constant flow state and alternating pressure and flow state, the calibrated particle size counter and the standard counter are connected to the same position in the system to test the performance of the calibrated particle size counter. This article introduces a real-time measurement and control system with PLC as the control core and its application in the dynamic calibration test bench of oil contamination detection instrument.

According to the requirements of system control and scalability, CJ series PLC is selected, and CJ1G-CPU43P is used as the CPU. Among the functional modules, CJ1W-ETN21 communication module is used to achieve communication connection with the upper computer; CJ1WAD081-V1 analog input module is responsible for data acquisition of various sensors; The CJ1W-TC103 temperature module is used to collect system temperature signals, while the CJ1W-DA041 analog output module is used to send control signals to various proportional control amplifiers and frequency converters. CJ1GCU43P has built-in loop control, which is applied in this system as follows: two PID controllers are mainly used to control the proportional relief valve and proportional flow valve respectively (see Figure 2). In PID control, the loop control sets the operating and output parameters of the PID module in the User Link Table, and the pressure and flow PID control outputs the MV value in the DM area.

The test bench has the following advantages:

(1) The combination of PLC logic interlock and external physical interlock greatly reduces misoperation;

(2) The equipped test bench is fully functional, capable of calibrating particle size counters and performing performance tests on other products, meeting the economic needs of the test bench;

(3) The application of CJ1G-CPU43P has improved the experimental accuracy.