Main instruments and meters for cleanroom performance testing

In the daily maintenance of cleanrooms, the role of instruments and meters is equivalent to a mirror, supervising the operation status of cleanrooms. This article discusses the application of measuring instruments in cleanrooms from the perspective of cleanrooms.

Overview of main instruments and meters

1. Wind pressure test instrument: It is mainly used to measure the micro-pressure difference between cleanrooms and between clean and non-clean areas. It can also use the pressure difference method to measure wind speed and calculate air volume.

(1) Liquid pressure gauge:Liquid pressure gauge has the advantages of easy use, low price, high accuracy, and easy manufacturing and installation, but it has the disadvantages of limited measurement range and fragile glass tube.

Common working liquids include alcohol, water, mercury, etc. In cleanroom measurements, alcohol and water are the main ones.

Liquid pressure gauges mainly include:U-tube pressure gauge, inclined tube pressure gauge, and compensated pressure gauge.

(2) Spring pressure gauge:The spring pressure gauge is made based on the principle that the spring element deforms under the measured pressure, and its deformation is a function of the measured pressure. Its advantages are simple structure, easy to carry, easy to install, and low price. Commonly used spring pressure gauges include:spring tube pressure gauge, diaphragm tube pressure gauge and membrane core pressure gauge.

(3) Electrical manometer:An electrical manometer is a manometer that uses piezoelectric principle or electrical methods such as resistance change under high pressure to measure pressure. It is suitable for measuring pressure that changes very quickly, has very high values or is close to absolute vacuum.

2. Wind speed and air volume test instruments:

(1) The working principles of wind speed measuring instruments include:mechanical type, heat dissipation rate type and dynamic pressure measurement type.

a. Mechanical anemometer:such as wing-shaped anemometer, which uses the motive pressure of flowing gas to drive the mechanical device to display its flow rate.

b. Heat dissipation rate anemometer:It is made based on the fact that the heat dissipation rate of the heated object in the fluid is proportional to the fluid flow rate. By measuring the heat dissipation rate of the sensor, the flow rate of the fluid can be measured. Commonly used heat dissipation rate anemometers include:hot wire anemometers and hot bulb anemometers.

(2) Air volume measuring instrument:The duct method is often used to test the total air volume in the cleanroom, and the air outlet method is often used to measure the return air volume of each room. The principle is to multiply the average wind speed by the cross-sectional area.

3. Cleanliness tester:

a. Instrument for detecting dust particles:At present, the detection of cleanliness in cleanrooms mainly uses light scattering dust particle counters, which are divided into incandescent light dust particle counters and laser dust particle counters.

Its principle is to use the scattering phenomenon of light by particles in the air, convert the light pulse signal of the particles in the sampled air into the corresponding electrical pulse signal to determine the number of particles, and use the relationship that the light scattering intensity of the particles is proportional to the square of the particle size to measure the size of the particle size.

b. Instrument for detecting biological particles:At present, the detection methods of biological particles mainly use culture medium method and filter membrane method, and the instruments used are divided into floating bacteria sampler and sedimentation bacteria sampler.

The main types of floating bacteria samplers are:solid impact samplers, centrifugal air microbial samplers, cyclone microbial samplers, liquid impact microbial samplers, filtration microbial samplers and large-capacity electrostatic precipitation samplers.

The main types of sedimentation bacteria samplers are:high-pressure sterilizers, constant temperature incubators and culture dishes.

4. Temperature tester:commonly known as thermometer, according to its working principle, it can be divided into expansion thermometer, pressure thermometer, thermocouple thermometer and resistance thermometer.

a. Expansion thermometer:divided into solid expansion thermometer and liquid expansion thermometer.

b. Pressure thermometer:It can be divided into gas-filled pressure thermometer and steam-filled pressure thermometer.

c. Thermocouple thermometer:It is made according to the principle of thermoelectric effect. When the temperature of two different metal nodes is different, there will be electromotive force. If the temperature of one point is known, the temperature of another point can be calculated by measuring the electromotive force.

d. Resistance thermometer:Based on the fact that the resistance of a certain metal, its alloy or semiconductor will change with temperature, the temperature can be measured by accurately measuring the resistance. The advantages of resistance thermometer are:high accuracy, sensitivity, fast response;wide temperature measurement range;no need for cold node compensation;can be used for long-distance temperature measurement.

5. Humidity tester:Humidity testers can be divided into dry-bulb thermometers, hair thermometers, electric thermometers, etc. according to their principles.

6. Noise tester:The principle of the noise tester is to use a capacitive microphone to convert sound energy into electrical energy, and then go through a series of processing such as amplifiers and detectors to finally give the sound pressure value.

7. Illuminance tester:The principle of the commonly used portable illuminance meter is to use a photosensitive element as a probe. When there is light, a photocurrent will be generated. The stronger the light, the greater the photocurrent. When measuring the current, the illuminance can be measured.