Teledyne 300E Instruction Manual page 176

THEORY OF OPERATION
CO MEASURE AND REFERENCE: These are the primary signals that are used in the
computation of the CO concentration. They are the demodulated IR-Sensor signals
from the Sync demodulator board.
SAMPLE PRESSURE AND FLOW: These are analog signals from two sensors that
measure the pressure and flow rate of the gas stream at the outlet of the Sample
Chamber. This information is used in two ways. First, the Sample Pressure is used
by the CPU to calculate CO Concentration. Second, the pressure and flow rate are
monitored as a test function to assist the user in predicting and troubleshooting
failures.
Thermistor Interface
This circuit provides excitation, termination and signal selection for several
negative-coefficient, thermistor temperature sensors located inside the analyzer.
They are:
SAMPLE TEMPERATURE SENSOR: The source of this signal is a thermistor located
inside the Sample Chamber of the Optical Bench. It measures the temperature of
the Sample Gas in the chamber. This data is used to during the calculation of the
CO concentration value.
BENCH TEMPERATURE SENSOR: This thermistor, attached to the Sample Chamber
housing, reports the current temperature of the chamber housing to the CPU as
part of the Bench Heater control loop.
WHEEL TEMPERATURE SENSOR: This thermistor attached a the heat-sync on the
GFC Wheel Motor assembly reports the current temperature of the wheel/motor
assembly to the CPU as part of the Wheel Heater control loop.
BOX TEMPERATURE SENSOR: A thermistor is attached to the Mother Board. It
measures the analyzer's inside temperature. This information is stored by the CPU
and can be viewed by the user for troubleshooting purposes via the front panel
display (see Section 11.1.2).
Analog Outputs
The analyzer comes equipped with four Analog Outputs: DAS, REC, TEST and a
fourth that is a spare.
REC and DAS Outputs: The first two, REC and DAS are normally set up to operate
in parallel so that the same data can be sent to two different recording devices.
While the names imply that one should be used for sending data to a chart recorder
and the other for interfacing with a datalogger, either can be used for both
applications.
176
Model 300E Carbon Monoxide Analyzer
Instruction Manual
P/N 04288 Rev: A