Atec 8000, Руководство по эксплуатации и обслуживанию, Страница: 35 / 80

Atmospheric Technology 29
4. Attach a certified calibrator in series with the MFC to record the flow rate. For
calibrating the Channel 1 MFC attach the calibrator to one of the port outlet
tubes. For calibrating the Channel 2 MFC, attach the calibrator to the
Channel 2 outlet tube.
If the calibrator is a direct volume measuring device (e.g. soap bubble, BIOS,
etc.) then you need to record the volumetric flow rate along with the
temperature and pressure. If the calibrator is a thermal device (e.g. mass
flow meter) then you need to record the reference temperature and pressure
for the calibrator.
5. Use the following equation to calculate the slope from the recorded calibration
data and desired sampler reference conditions, where:
PC=calibrator pressure (mm Hg)
TC=calibrator temperature (°K)
T=Sampler MFC reference temperature (°K)—normally 298 °K
PF=MFC factory reference pressure = 760 mm Hg
TF=MFC factory reference temperature = 273 °K
W=calibrator flow rate
F=sampler flow rate set
Slope = TF x PC x W x T
PF x TC x F x TF
To simplify, this equation reduces to:
Slope = 0.392 X PC X W
TC x F
for a sampler MFC reference condition of 25 °C and 760 mm Hg
For example, a volumetric calibrator is operated in series with the sampler to
check the flow rate at 3.8 ccpm. The “Calibrated Values” box is checked and
the sampler will be calibrated to display the flow rate at the normal EPA
reference conditions of 25°C and 760 mm Hg. During the calibration
procedure, the calibrator air flow is measured at 292°C and 740 mm Hg and
4.1 ccpm. The slope is calculated as: