Pneumatic Sensors; Sample Pressure Sensor; Vacuum Pressure Sensor - Teledyne T200 User Manual

A certain amount of fine, black dust may exit the catalyst, particularly if the analyzer is
subjected to sudden pressure drops (for example, when disconnecting the running pump
without letting the analyzer properly and slowly equilibrate to ambient pressure). To
prevent the dust from entering the reaction cell or the pump, the ozone destruct is equipped
with a quartz wool filter material.
P
NEUMATIC
Note
Three pneumatic sensors verify the flow and pressure levels of the gas streams. They are
located on a printed circuit assembly, called the pneumatic pressure/flow sensor board,
located just behind the sensor assembly. The measurements made by these sensors are used
for a variety of important calculations and diagnostics.

SAMPLE PRESSURE SENSOR

An absolute pressure transducer connected to the input of the NO/NO
measure the pressure of the sample gas before it enters the analyzer's reaction cell.
• In conjunction with the measurement made by the vacuum pressure sensor, this
"upstream" measurement is used to compute the sample gas sample flow rate and to
validate the critical flow condition (2:1 pressure ratio) through the sample gas critical
flow orifice (Section 6.2.2).
• If the Temperature/Pressure Compensation (TPC) feature is turned on (Section
6.9.2), the output of this sensor is also used to supply pressure data for that
calculation.

VACUUM PRESSURE SENSOR

An absolute pressure transducer connected to the exhaust manifold is used to measure the
pressure downstream from and inside the instrument's reaction cell.
The output of the sensor is used by the CPU to calculate the pressure differential
•
between the gas upstream of the reaction cell and the gas downstream from it and is
also used as the main diagnostic for proper pump operation.
If the ratio between the upstream pressure and the downstream pressure falls below
•
2:1, an Alert is triggered, and the sample flow rate will not display an actual value.
If this pressure exceeds 10 in-Hg-A, an Rx Press Alert is issued, even though the
•
analyzer will continue to calculate a sample flow up to ~14 in Hg.
If the Temperature/Pressure Compensation (TPC) feature is turned on (see Section
•
6.9.2), the output of this sensor is also used to supply pressure data for that
calculation.
083730200A DCN7962
S
ENSORS
The analyzer displays all pressures in inches of mercury
absolute (in-Hg-A), i.e. absolute pressure referenced against
zero (a perfect vacuum).
Teledyne API T200 NO/NO /NO Analyzer with NumaView™ Software
2 x
valve is used to
X
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