Teledyne T200, Operation Manual, Page: 309 / 425

Teledyne API
– T200 NO/NO
2
/NO
X
Analyzer Operation Manual Principles of Operation
307
13.3.3.3. THERMISTOR INTERFACE
This circuit provides excitation, termination and signal selection for several negative
coefficient, thermistor temperature sensors located inside the analyzer. They are:
REACTION CELL TEMPERATURE SENSOR: The reaction cell temperature
sensor is a thermistor embedded in the reaction cell manifold. This temperature is used
by the CPU to control the reaction cell heating circuit and as a parameter in the
temperature/pressure compensation algorithm.

The value of this signal is viewable via the front panel test function
RCEL TEMP
and the SIGNAL I/O function
RCELL_TEMP
.

It is recorded by the DAS system as the parameter
RCTEMP
.
BOX TEMPERATURE SENSOR: A thermistor is attached to the motherboard. It
measures the analyzer‟s inside temperature. This information is stored by the CPU and
can be viewed by the user for troubleshooting purposes through the front panel display.
It is also used as part of the NO, NO
x
and NO
2
calculations when the instrument‟s
Temperature/Pressure Compensation feature is enabled.

The value of this signal is viewable via the front panel test function
BOX TEMP
and
the SIGNAL I/O function
BOX_TEMP
.

It is recorded by the DAS system as the parameter
BOXTMP
.
INTERNAL SPAN GAS GENERATOR OVEN TEMPERATURE: This thermistor
reports the temperature of the optional internal span gas generator‟s NO
2
permeation
source to the CPU as part of a control loop that keeps the tube at a high constant
temperature (necessary to ensure that the permeation rate of NO
2
is constant). It is
stored and reported as test function IZS TEMP .

The value of this signal is viewable via the front panel test function
IZS TEMP
and
the SIGNAL I/O function
IZS_TEMP
.

It is recorded by the DAS system as the parameter
IZTEMP
.
Note
There are two thermistors that monitor the temperature of the PMT assembly:
One is embedded in the cold block of the PMT
’s TEC. Its signal is conditioned
by the PMT preamplifier PCA and reported to the CPU via the motherboard
(see Section 13.3.3.2).
The second is located on the PMT Preamplifier PCA and is used only as a
reference for the preamplifier circuitry. Its output is neither reported nor
stored.
06858E DCN7057