Calibration of particle counters
Primary calibration of particle counters
Primary calibration of particle counters proceeds according to SOP laboratory. SOP is processed on the basis od standard method ISO 21501-4 Determination of particle size distribution – Single particle light interaction methods – Part 4: Light scattering airborne particle counter for clean spaces. The methodology describes projection of calibration curve of particle counter, i.e. the dependence of threshold voltage on the actual particle size, and determination of particle concentration measuring correctness, and is suitable for particle counters with measuring ranges from 0.1 µm do 10 µm. Metrological sequence of determination of detected particles is ensured by using certified reference material - PSL particles (polystyrene latex), of manufacturer Duke Scientific Corp., US., and calibrated gauges.
Secondary calibration of particle counters
Secondary calibration proceeds according to SOP laboratory. The methodology is intended for calibration of sizes and numbers of particles measured by particle counters, used as working gauges. The methodology is based on standard method JIS B 9921:1997 - Attachment 2 - Test of relative comparison, and on standard method ISO 21501-4:2007, points 4.7 (air flow through counter), 4.8 (sampling time) and Attachment D - counting error. The calibration is executed by comparing the values of size and number of particles of polydisperse, mainly atmoshperic aerosol, measured by calibrated gauge, to the values of size and number of particles measured by counter, designated as ethalon. Ethalon must have valid primary calibration according to standard method ISO 21501-4:2007 with sequence to reference material - PSL particles (polystyrene latex) with certified size of particles and dispersity.
Determination of calibration uncertainties
Determination of uncertainties of executed calibrations of particle counters conforms to the EA-4/02 document "Methodology of stating measuring uncertainties in calibrations"
Certification of particle counter calibrations
Calibration laboratory considered the possibility of certification at the The Czech Accreditation Institute (CIA) and has a system in place, coforming to the CIA accredited laboratory. However, such certification appears inconvenient in terms of economy, with regard to low number of executed calibrations (approx. 50 per year). The price of calibration would rise twice to three times. If customer is not satisfied with demonstration of calibration sequence of calibrations, stated in the calibrations sheets of the lab, and needs a certified document of calibration, those calibrations can be executed under the supervision of the Czech Metrology Institute (CMI) which issues a report of calibration evaluation to every calibration sheet. Thus the calibration has same validity as if was done by CMI, in the supervisory authorities´ point of view. If customer is interested in calibration under the supervision of CMI, the order of calibration has to be addressed to:
Český metrologický institut (Czech Metrology Institute)
Primary Metrology Laboratory, Department for radiometric and photometric quantities
V botanice 4
150 72 Praha 5
To accept an instrument for calibration it has to be in good technical condition and equipped with technical manual to be used if needed; instruments, adjustment of which (setting of threshold values in calibration) is executed by means of PC programme, must be accompanied by relevant programme and service intstructions. (some manufacturers provide this information on internet, if you do not have this documentation at disposal, please contact us before placing an order)
Calibration of aerosol photometers (nephelometers)
Aerosol photometers are instruments scanning light diffused by a cloud od particles, integrally from the area of gauge chamber, the measured aerosol runs through which. The scanned intensity of diffused light is the criterion of particle concentration for aerosol consisted of particles of same size and refraction index, or for polydisperse aerosols with constant disperse composition of particle size. Nephelometers are used mainly for measuring penetration of aerosols through filters and filter systems, and for defectoscopic tests of filter equipment. These measurings are executed artificially by means of prepared test aerosols produced for this particular purpose by designed aerosol generators. Aerosol generators ensure, on the condition of maintaining operating conditions,distribution of aerosol with constant disperse composition of aerosol particle size and, as a matter of course, also keeping the same particle shape and refraction index. For precisely defined test aerosol, the information about the instrument, representing the intensity of diffused light can be converted to weight concentration of test aerosol through the calibration by means of gravimetric method. Measuring has metrological sequence to CMI ethanols.
Determination of calibration uncertainties
Determination of calibration uncertainties conforms to the EA-4/02 document "Methodology of stating measuring uncertainties in calibrations"