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Principles Of Operation Model T101 Instruction Manual
258
10.3.7. PNEUMATIC SENSORS
The T101 uses two pneumatic sensors to verify gas streams. These sensors are located
on a printed circuit assembly, called the pneumatic pressure/flow sensor board.
10.3.7.1. Sample Pressure Sensor
An absolute pressure transducer plumbed to the input of the analyzer’s sample chamber
is used to measure the pressure of the sample gas before it enters the chamber. This
upstream used to validate the critical flow condition (2:1 pressure ratio) through the
instrument’s critical flow orifice (Section 10.3.3.1). Also, if the temperature/pressure
com
pensation (TPC) feature is turned on (Section 10.7.3), the output of this sensor is
also used to supply pressure data for that calculation.
The actual pr
essure measurement is viewable through the analyzer’s front panel display
as the test function PRESS.
10.3.7.2. Sample Flow Sensor
A thermal-mass flow sensor is used to measure the sample flow through the analyzer.
This sensor is also mounted on the pneumatic pressure/flow sensor board upstream of
the sample chamber. The flow rate is monitored by the CRT which issues a warning
message (SAMP FLOW WARN) if the flow rate is too high or too low.
The flow rate of the sample gas is viewable via the front panel as the SAMP FL test
function.
07266B DCN6485