Parameters Affecting Operation; Flow Calibration; Density - Ametek 303B User Manual

Parameters Affecting Operation

1-6 | 303B Moisture Analyzer Manual
Interfering and Contaminating
Some substances will immediately contaminate the cell and cause incor-
rect readings. Typical examples are graphite dust, hydrogen fluoride, and
ammonia.

Flow Calibration

The 303B is an easy to operate, but flow dependent instrument. To ob-
tain an accurate moisture measurement the operator must set the sample
flow to the equivalent of 100 mL/min at 1 atmospheric pressure and 25°C
(77°F). If sample flow is off by ten percent, the measurement will general-
ly also be off by ten percent. If the user is to achieve the specified accura-
cy, the simple flow setting procedure described in Chapter 3-5, Sample
System Hook Up, steps 4, 5 and 6, must be performed.
The 303B comes equipped with sample and bypass flow meters. These
flow meters are not high precision devices and are to be used exclusively
as flow indicators. We suggest the operator use a relatively high precision
flow meter, such as a bubble-o-meter (soap bubble flow meter) to set the
sample flow through the monitor. Of course, the external flow meter must
be calibrated for the sample gas and the bubble-o-meter must be correct-
ed for temperature and pressure.
Operating at a flow other than 100 mL/min at 25°C (77°F) and 1 atmos-
phere requires a display reading correction to obtain the proper ppm. In
general, doubling the flow doubles the indicated moisture reading.
No cell calibration is needed because the measurement is quantitative and
its response to moisture is linear from less than 1 to 1000 ppm, or 50 lb/
MMscf.

Density

Sample flow must be readjusted if gases of different densities are ana-
lyzed.
A flow meter will not be at the same point for a flow of 100 mL/min

for two gases of different densities
NOTE
Flow meters are calibrated for a specific gas at a specific temperature and