Table of Contents
Advertisement
Teledyne API - Model T200H/T200M Operation Manual
8.5.9.2. Sensor Inputs
07270D DCN7141
The A/D consists of a voltage-to-frequency (V-F) converter, a programmable logic device
(PLD), three multiplexers, several amplifiers and some other associated devices. The V-F
converter produces a frequency proportional to its input voltage. The PLD counts the
output of the V-F during a specified time period, and sends the result of that count, in the
form of a binary number, to the CPU.
The A/D can be configured for several different input modes and ranges but in the is used
in uni-polar mode with a +5V full scale. The converter includes a 1% over and under-
range. This allows signals from -0.05V to +5.05V to be fully converted.
For calibration purposes, two reference voltages are supplied to the A/D converter:
Reference ground and +4.096 VDC. During calibration, the device measures these two
voltages, outputs their digital equivalent to the CPU. The CPU uses these values to
compute the converter's offset and slope and uses these factors for subsequent
conversions. See Section 6.13.5.4 for instructions on performing this calibration.
The key analog sensor signals are coupled to the A/D converter through the master
multiplexer from two connectors on the motherboard. Terminating resistors (100 kΩ ) on
each of the inputs prevent cross-talk between the sensor signals.
PMT DETECTOR OUTPUT: This signal, output by the PMT preamp PCA, is used in the
computation of the NO, NO
corner of the front panel display and output through the instruments analog outputs and
com ports.
PMT HIGH VOLTAGE POWER SUPPLY LEVEL: This input is based on the drive
voltage output by the PMT pram board to the PMT's high voltage power supply (HVPS).
It is digitized and sent to the CPU where it is used to calculate the voltage setting of the
HVPS and stored in the instruments memory as the test function HVPS. HVPS is
viewable as a test function (see Section 6.2.1) through the analyzer's front panel.
PMT TEMPERATURE: This signal is the output of the thermistor attached to the PMT
cold block amplified by the PMT temperature feedback circuit on the PMT preamp board.
It is digitized and sent to the CPU where it is used to calculate the current temperature of
the PMT.
This measurement is stored in the analyzer. Memory as the test function PMT TEMP
and is viewable as a test function (see Section 6.2.1) through the analyzer's front panel.
NO
CONVERTER TEMPERATURE: This parameter is measured with a Type-K
2
thermocouple attached to the NO
the circuitry on the relay board. It is sent to the CPU and then digitized and is used to
calculate the current temperature of the NO
reported as test function MOLY TEMP.
SAMPLE GAS PRESSURE: This is measured upstream of the reaction cell, stored in the
DAS and reported as SAMPLE. The vacuum gas pressure is measured downstream of
the reaction cell and is stored in the DAS and reported as RCEL. For more information
on these sensor's functions see Section 8.3.10.
O
GAS FLOW This sensor measures the gas flow upstream of the ozone generator,
3
stored in the DAS and reported as test function OZONE FL. For more information on
this sensor's function see Section 8.3.10.
and NO
concentrations displayed at the top right hand
2
x
converter heater and its analog signal is amplified by
2
converter. It is also stored in the DAS and
2
Principles of Operation
299
Advertisement
Table of Contents
