What Is a Digital Dust Meter?
A digital dust meter is a compact measuring instrument used to measure the concentration of dust in the air of soil, rocks, minerals, metals, and carbon, which are substances required to be measured in the working environment.
A digital dust meter can accurately and easily measure dust concentration (mg/m3) by calculating the number of dust counts per unit time (cpm) x K value (mass concentration conversion factor: mg/m3/cpm).
The K value (mass concentration conversion coefficient: mg/m3/cpm) is a coefficient that converts the number of dust counts into dust concentration. It is the slope of a straight line obtained by using the fact that the amount of scattered light (cpm) and concentration (mg/m3) of the same type of dust are linearly proportional.
Dust detection methods include the scattered light method, particle counting method, absorption spectrophotometry, and condensation nucleus particle counting method.
Applications of Digital Dust Meters
This section describes the uses of a digital dust meter.
A digital dust meter is used in indoor workplaces that emit significant amounts of dust of earth, rocks, minerals, metals, or carbon.
Therefore, dust concentration control is required in indoor workplaces where metal welding, grinding, cutting, or excavation work is frequently performed.
Furthermore, depending on the measurement principle, it is known that the sensitivity may vary depending on the type and shape of dust, and it is required to control the measurement results keeping in mind that all suspended particulate matter such as smoke and mist are susceptible.
Principle of Digital Dust Meters
This section describes the principles and characteristics of a digital dust meter.
The scattered light method uses a suction fan to draw in airborne dust continuously from an air inlet and irradiate the dust with white light or laser light as a light source. The amount of scattered light emitted from the dust is continuously detected at the light receiving unit, and the amount of light is converted into an electrical signal by a photoelectric conversion element. This value is treated as the amount of scattered light per unit time (cpm: counts per minute). This concentration value is multiplied by the K value (mass concentration conversion factor) to obtain the mass concentration of dust (mg/m3).
The particle counting method is used to measure extremely clean environments. A thin, undisturbed stream of air is continuously generated to capture airborne dust particles. A strong beam of light, such as a laser beam, is used as the light source. The scattered light from each individual dust particle is detected in the photosensor and converted into an electrical signal by a photoelectric conversion element. The particle size distribution is determined from the intensity of the scattered light, and the number of particles per unit volume (particles/cm3) is determined from the number of counts. This concentration value is multiplied by the K value (mass concentration conversion factor) to obtain the mass concentration of dust (mg/m3).
The absorbance spectrophotometry method continuously captures airborne dust particles and irradiates them with white light or laser light as a light source, converting the amount of light attenuation by the dust particles into an electrical signal using a photoelectric conversion element. The relative concentration proportional to the logarithm of this light attenuation (transmittance) is calculated to give the dust concentration (mg/m3).
The condensation nucleus particle counting method is used to measure dust concentration when the dust concentration is low. The light scattering particle counting method is applied by condensing and growing dust in a supersaturated vapor atmosphere. The measured value is the total number concentration above the minimum measurable particle size, which has the disadvantage of no particle size information.