Teledyne 3010MA, Руководство по эксплуатации, Страница: 75 / 88

Paramagnetic O2 Purity Analyzer Analysis Unit
Teledyne Analytical Instruments
75
6.4 Sample System
The paramagnetic sensor used in the Model 3010MA is a partial
pressure device and is sensitive to pressure variations both at the point of
entry into the system and the sample exit (atmospheric pressure). For
example, a 1% change in vent pressure will cause a corresponding 1%
variation in the oxygen reading.
For higher accuracy, a pressure compensation circuit is installed to
compensate for vent pressure fluctuations. A 1/8 inch line continuously
samples the pressure at the sensor outlet in the Analysis unit and delivers
it to the pressure compensation circuit within the Control Unit. The raw
output from the sensor is corrected for pressure variation using a baseline
pressure set during instrument calibration. The output is adjusted
electronically based on the pressure differential between the present
reading and the baseline set during the last calibration.
The linear range of the uncorrected sensor output is 0-1.2 V dc. For
proper operation, the raw output must be adjusted to 0 V dc at 95% O
2
and
1 V dc at 100% O
2
. This allows the sensor output to remain linear during
minor atmospheric fluctuations. The raw sensor output can be accessed
form the alphanumeric display by using the System key.
On the inlet side, the Model 3010MA is supplied with an externally
mounted flow restrictor to limit the sample flow to 300 -1000 SCCM. The
actual restrictor recommended depends on the users sample pressure. Note
that the restrictor can be replaced with a metering valve for more
flexibility. The standard units are supplied with P N: R2533. Table 6-3
identifies restrictors available for the pressure ranges shown as well as
available metering valves.
Table 6-3: Pressure Ranges of Available Restrictors
PRESSURE RANGE TAI RESTRICTOR
2-5 psig TAI P/N R2532
5-15 psig TAI P/N R2533
10-20 psig TAI P/N R2534
15-30 psig TAI P/N R2535
Brass metering valve TAI P/N V744
SS metering valve TAI P/N V745