Teledyne 400E Instruction Manual page 234

THEORY OF OPERATION
GAS FLOW SENSOR: This sensor measure the flow rate of the sample gas through
the instrument. This information is used as a diagnostic tool for determining gas
flow problems
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
near the Absorption Tube inside the Optical Bench assembly. It measures the
temperature of the Sample Gas in the chamber. This data is used to during the
calculation of the O
UV LAMP TEMPERATURE SENSOR: This thermistor, attached to the UV Lamp in the
optical Bench reports the current temperature of the Lamp to the CPU as part of the
Lamp Heater control loop.
IZS LAMP TEMPERATURE SENSOR: This thermistor attached to the UV Lamp of the
O generator in the IZS Option reports the current temperature of that Lamp to the
3
CPU as part of control loop that keeps the lamp constant temperature.
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: A1, A2, A4 and a fourth
that is a spare.
A1 and A2 Outputs: The first two, A1 and A2 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.
Both of these channels output a signal that is proportional to the O3 concentration
of the Sample Gas. The A1 and A2 outputs can be slaved together or set up to
operated independently. A variety of scaling factors are available, See Section 6.5
for information on setting the range type and scaling factors for these output
channels.
Test Output: The third analog output, labeled A4 is special. It can be set by the
user (see Section 6.5.7) to carry the current signal level of any one of the
parameters accessible through the TEST menu of the unit's software.
234
concentration value.
3
Model 400E Ozone Analyzer
Instruction Manual
P/N 04316 Rev: B