As the core equipment for simulating special environments, the debugging quality of the high and low temperature alternating humidity testing machine directly affects the accuracy of the test results and the service life of the equipment. The standardized debugging process will be carried out from four aspects: preliminary preparation, core system debugging, parameter verification, and security confirmation.
1、 Preparation work before debugging
1. Environmental adaptability check
-Ensure stable laboratory power supply voltage (within ± 5% fluctuation range) and grounding resistance<4 Ω;
-Reserve a maintenance space of ≥ 80cm around the equipment, and ensure that the ventilation openings are unobstructed;
-The water source should be deionized water or purified water, with a water conductivity of ≤ 5 μ S/cm, to avoid impurities blocking the humidifier.
2. Initial inspection of mechanical structure
-Check the integrity of the sealing strip of the box, and after closing the door, forcefully push the door body to confirm that there are no obvious gaps;
-Adjust the height of the wheels to place the equipment horizontally, with the level bubble centered;
-Clean the dust accumulation on the filter screens of the evaporator and condenser to ensure smooth air ducts.
2、 Core system sub item debugging
1. Refrigeration system debugging
-After starting the compressor, observe the values on the high-pressure gauge (about 1.8~2.2MPa) and low-pressure gauge (about 0.4~0.6MPa);
-Set a target temperature of -40 ℃ and run until the temperature stabilizes. The measured temperature difference should be ≤ ± 2 ℃;
-Check the oil level of the refrigeration unit. If the oil level displayed on the oil mirror is below the scale line, special refrigeration oil should be replenished.
2. Joint debugging of heating and dehumidification system
-Turn on the heating module separately and raise the temperature to 85 ℃ at a rate of 5 ℃/min to check the working status of the heating tube;
-Conduct a 90% RH high humidity test, observe the operating frequency of the dehumidification solenoid valve, and control humidity fluctuations within ± 3% RH;
-Alternating between cold and hot shocks (e.g. -20 ℃) ↔ After 3 cycles at 60 ℃, check the stability of the instrument display.
3. Calibration of humidification system
-Dismantle the water tank cover plate and use an electronic scale to weigh whether the water pump flow rate meets the design value;
-Adjust the water level float valve to ensure that the automatic water replenishment function responds promptly when the liquid level is low;
-Adjust the angle of the atomizing nozzle to 45 degrees diagonally upwards to avoid directly flushing the surface of the test sample.
3、 Optimization of Control System Parameters
1. Sensor calibration
-Compare the actual temperature inside the box with a second-class standard platinum resistance thermometer and correct the PID parameters of the temperature controller;
-Hang the dry and wet bulb gauze at a distance of 1/3 from the air outlet, and calibrate the humidity sensor with a precision dew point meter;
-After inputting the correction coefficient, conduct a no-load temperature deviation test (uniformity ≤ 2 ℃, fluctuation ≤ 1 ℃).
2. Program running verification
-Develop a typical testing program (such as -40 ℃ →+85 ℃ → 95% RH cycle), set the heating and cooling rate to 3 ℃/min;
-Place a standard copper load (not exceeding 1/3 of the box volume) and monitor the dynamic recovery time;
-Record continuous operation data for 48 hours, draw temperature and humidity curves, and check for drift phenomenon.
4、 Safety and performance confirmation
1. Alarm function test
-Manually triggering overload protection, water shortage alarm, over temperature protection, verifying sound and light alarm and automatic shutdown functions;
-Check the door lock interlock device and immediately cut off the heating/humidification power supply when opening the door.
2. Insulation performance testing
-When using a 500V megohmmeter to measure the insulation resistance between phase sequences and between live parts and the casing in a power-off state, it should be>2M Ω;
-Grounding continuity test, the resistance between the grounding point and the metal casing of the equipment is less than 0.1 Ω.
3. Final acceptance criteria
-Under no-load conditions, temperature deviation is ≤± 2 ℃, humidity deviation is ≤± 5% RH;
-When operating at full load, the cooling rate should be ≥ 1 ℃/min and the heating rate should be ≥ 3 ℃/min;
-Run continuously for 72 hours without any faults and shut down, with a noise level of<75dB (A).
Systematic debugging can effectively eliminate the impact of transportation stress on equipment after leaving the factory, and improve the accuracy of temperature and humidity control. It is recommended to have a professional technician complete the full calibration before use, and then conduct a simplified performance verification every quarter to ensure that the equipment is always in the best working condition.