Clean room performance test
First, the wind pressure test mainly measures the micro-pressure difference between clean rooms and clean areas and non-clean areas. The pressure difference method can also be used to measure the wind speed and calculate the air volume. The instruments used are:
① Liquid pressure gauge: liquid pressure gauge has the advantages of easy to use, low price, high accuracy, easy to manufacture and install, but it has the disadvantages of limited measuring range, fragile glass tube and so on.
Commonly used working liquids are: alcohol, water, mercury, etc., mainly alcohol and water in clean room measurement.
Liquid pressure gauge mainly includes: U-tube pressure gauge, inclined tube pressure gauge, compensation type pressure gauge.
② Spring pressure gauge: spring pressure gauge is made according to the principle that the spring element deforms under the measured pressure, and the deformation is a function of the measured pressure. Its advantages are simple structure, easy to carry, convenient installation and low price.
Commonly used spring manometer mainly include: spring tube manometer, diaphragm tube manometer and membrane core manometer.
③ Electrical manometer: Electrical manometer is the use of piezoelectric principle or resistance change under high pressure and other electrical methods to measure the pressure of the pressure gauge, suitable for measuring the change of very fast, very high value or almost absolute vacuum pressure.
Two, wind speed, air volume, cleanliness and other performance index testing instruments include:
① The principle of anemometer is: mechanical, heat dissipation and dynamic pressure measurement.
a. Mechanical anemometer: such as an aerofoil anemometer, it is an instrument that uses the primary dynamic pressure of a flowing gas to push the mechanism to display its velocity.
b. Heat dissipation anemometer: It is made according to the heat dissipation rate of the heated object in the fluid and the velocity of the fluid. The heat dissipation rate of the sensor is determined, that is, the velocity of the fluid can be measured.
Commonly used heat dissipation type anemometer are: hot wire anemometer and hot ball anemometer.
(2) Air volume measuring instrument: the total air volume in the clean room is commonly tested by the air duct method. The air volume returned to each room is measured by the tuyere method. The principle is the average wind speed multiplied by the section area.
③ Cleanliness tester:
a. Dust particle detection instrument: At present, the detection of clean room cleanliness is mainly light scattering dust particle counter, which is divided into incandescent light dust particle counter and laser dust particle counter.
Its principle is to use the scattering phenomenon of light particles in the air to convert the light pulse signal of sampled particles in the air into the corresponding electrical pulse signal to measure the particle number of particles, and use the light scattering intensity of particles to measure the particle size of particles in direct proportion to the square of particle size.
b. Biological particle detection instrument: at present, the detection methods of biological particles mainly use medium method and filter membrane method, the instruments used are divided into plankton sampler and settling bacteria sampler.
Plankton sampler mainly includes solid impact sampler, centrifugal air microorganism sampler, cyclone microbiological sampler, liquid impact microbiological sampler, filter microbiological sampler and large capacity electrostatic sedimentation sampler.
Settling bacteria sampler mainly includes: autoclave, constant temperature incubator and petri dish.
(4) Temperature tester: general thermometer, according to its principle of action can be divided into expansion thermometer, pressure thermometer, thermocouple thermometer and resistance thermometer.
a. Expansion thermometer: solid expansion thermometer and liquid expansion thermometer.
b. Pressure thermometer: can be divided into inflatable pressure gauge thermometer and steam filled pressure gauge thermometer.
c. Thermocouple thermometer: is made according to the principle of thermoelectric effect, when two different metal joint temperature is not at the same time there will be electromotive force, such as known temperature, measured electromotive force can calculate the temperature of another point.
d. Resistance thermometer: The resistance based on certain metals and their alloys or semiconductors varies with temperature. Accurately measuring the resistance will measure the temperature.
The advantages of resistance thermometer are: high precision and sensitivity, fast response; Wide range of temperature measurement; No cold node compensation; Can be used for remote temperature measurement.
⑤ Humidity tester: According to its principle, humidity tester can be divided into wet and dry bulb thermometer, hair thermometer, electric thermometer, etc.
Its principle is to use a capacitive microphone to change sound energy into electric energy, and then through a series of amplifier, detector and other processing, finally give the sound pressure value.
⑦ illuminance tester: commonly used portable illuminance meter its principle is to use a photosensitive element as a probe, when there is light will produce photocurrent, the stronger the light current is, the current can be measured when the illuminance.