Scattering Coefficient Calibration; Internal Span Check - Thermo Scientific personalDATARAM pDR-1000AN Instruction Manual

The duration of this comparison run should be sufficient to collect a mass of at least
1 mg on the reference filter (in order to permit accurate weighing of the collected
mass by means of an analytical balance). The time-weighted average (TWA) reading
of the personalDataRAM can be used to estimate the required sampling time to
collect the above-mentioned mass on the filter. To estimate the required sampling
time (ET as measured on the personalDataRAM) in minutes, read the TWA value
(see Section 8.3) after an elapsed time (ET) of one minute or more, and apply the
following relationship:
For example, if TWA = 2.5 mg/m
If the TWA value changes significantly as the run proceeds, recalculate the required
ET accordingly.
At the end of the run (after time ET has elapsed), record TWA, ET and the flow rate
Q used to sample the air. Weigh the filter on an analytical balance and obtain Δm,
the mass increment due to the collected particles.
Calculate the average gravimetric concentration C, as follows:
Compare the recorded value of TWA and the calculated value C, and calculate the
calibration factor to be programmed into the personalDataRAM (see Section 9.0) as
follows:
For example, if C was found to be 3.2 mg/m
3
2.5 mg/m , the CAL FACTOR equals 1.28. Select this value on the PC, as described
in Section 9.0. This completes the gravimetric calibration of the personalDataRAM
for a specific aerosol.
13.3

Scattering Coefficient Calibration

Users interested in using the personalDataRAM for scattering coefficient
measurements (e.g., for atmospheric visibility monitoring) should contact the
factory. A special primary Rayleigh scattering calibration for such purpose can be
performed by the factory.
13.4

Internal Span Check

The zeroing procedure (see Section 8.1) and the resulting normal diagnostic display
of "CALIBRATION: OK" (step 2) informs the user that the instrument's calibration
agrees with the original factory setting. This is an internal span check that consists of
an automatic comparison between the initial (factory) optical background of the
personalDataRAM (registered in its non-volatile memory), and the current optical
background sensed during the zeroing sequence.
ET ≥ 500/TWA
3
, then ET ≥ 200 minutes (approximately 3 hours).
C = 1000 Δm/ETxQ
CAL FACTOR = C/TWA
3
, and TWA had been determined to be
36