In the previous sectionTemperature Test Chamber Testing Standard | I, we introduced common types of temperature and humidity tests, how to handle samples for temperature and humidity tests, what are the requirements for sample loading, and what are the preparations before testing. In this issue, we introduce how to select the appropriate temperature and humidity test chamber (e.g. constant temperature and humidity test chamber) according to the test standard.
Temperature and humidity test chamber calibration items
Temperature deviation;
Relative humidity deviation;
Temperature uniformity;
Temperature fluctuation;
Temperature rise and fall characteristics;
Wind speed.
Temperature measurement using platinum resistance, thermocouple or other temperature sensors composed of temperature measurement system; relative humidity measurement using dry and wet bulb thermometer or other sensors composed of humidity measurement system; wind speed measurement using a variety of anemometers, the inductance of which is not greater than 0.05 m/s.
Constant / alternating humidity and heat test calibration steps
01 Temperature test chamber for constant damp heat test
Install temperature and humidity sensors at each measurement point according to regulations;
Load the calibration load into the working space;
Measure the wind speed at the relative humidity measurement point or all test points;
Slowly increase the temperature to 40°C. The rate of temperature rise should not exceed 1℃/min (up to the average of every 5 min), the temperature value of the center point should be measured every 5 min and recorded;
Make the relative humidity reach (93+2-3 )% within 2h;
Since the temperature and humidity of the working space reaches the specified value and remains stable, measure the temperature and humidity values of all measurement points every 2 min for at least 30 min, a total of 15 times, and record them.
02 Temperature test chamber for alternating humidity and heat test
Install the temperature and humidity sensors at the measuring points as specified;
Install the test load into the working space;
Measure the wind speed at the relative humidity measurement point if necessary;
Make the temperature of the working space reach 25℃±3℃ and keep the relative humidity between 45%~75%;
In 1h, so that the relative humidity of the workspace is not less than 95%, from this moment onwards, so that the temperature and humidity of the workspace in accordance provides the procedure, that is, according to the “warming - high temperature and high humidity - cooling - low temperature and high humidity,” continuous changes.
In the warming stage, every 5 min to measure the temperature and humidity value of the center point (0, 0h) once; in the high temperature and high humidity stage, every 2 min to measure the temperature and humidity value of all measurement points once, at least 30 min, a total of 15 times; in the high temperature and high humidity stage, that is, the end of the cooling phase, that is, before the start of the phase of 30 min, every 2 min to measure the temperature and humidity value of all measurement points once, a total of 15 times; from since the beginning of the cooling phase, every 5 min to measure the temperature and humidity value of the center point (0, 0h) 1 time, until the temperature of all measuring points in the workspace to 25 ℃ ± 3 ℃, relative humidity is not less than 95%, that is, into the low-temperature and high humidity stage; in the low-temperature and high humidity stage, every 2 min to measure the temperature and humidity value of all measuring points 1 time, a total of 15 times.
All measurements should be recorded.
Calibration results
01 Temperature test chamber for constant damp heat test
Calculate the temperature uniformity, temperature fluctuation, temperature deviation, relative humidity deviation, wind speed and heating rate according to the formula in the standard and the recorded data. If the calculation results meet the requirements of the standard, the equipment complies with the standard.
02 Temperature test chamber for alternating humidity and heat test
Depict the characteristic curve of temperature rise and fall, and calculate the temperature and humidity deviation and temperature fluctuation according to the formula in the standard. The test results, temperature and humidity deviation and relative humidity deviation should be consistent with the relevant provisions of test standards; rise and fall of the temperature characteristic curve should be within the range of permissible variations in temperature and humidity specified in relative test standards. The characteristic curve of temperature rise should rise continuously; the characteristic curve of temperature fall should fall continuously and should not be jagged.
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