Photo-Detector Temperature Control; Dark Calibration Switch; Electric Test Switch; Relay Board - Teledyne T300 Operation Manual

Teledyne API – Model T300/T300M CO Analyzer

13.4.3.3. PHOTO-DETECTOR TEMPERATURE CONTROL

13.4.3.4. DARK CALIBRATION SWITCH

13.4.3.5. ELECTRIC TEST SWITCH

13.4.4. RELAY BOARD

13.4.4.1. HEATER CONTROL

13.4.4.2. GFC WHEEL MOTOR CONTROL

06864B DCN6314
The sync/demod board also contains circuitry that controls the IR photo-detector's
Thermal Electric Coolers (TEC). A drive voltage, PHT DRIVE, is supplied to the
coolers by the sync/demod board which is adjusted by the sync/demod board based on a
return signal called TEC control which alerts the sync/demod board of the detector's
temperature. The warmer the detector, the harder the coolers are driven.
PHT DRIVE is one of the Test Functions viewable by the user via the form panel.
Press <TST or TST> until it appears on the display.
This switch initiates the Dark Calibration procedure. When initiated by the user (See
Section 9.6.1 for more details), the dark calibration process opens this switch,
interrupting the signal from the IR photo-detector. This allows the analyzer to measure
any offset caused by the sync/demod board circuitry.
When active, this circuit generates a specific waveform intended to simulate the function
of the IR photo-detector but with a known set of value which is substituted for the
detector's actual signal via the dark switch. It may also be initiated by the user (See
Section 5.4 for more details).
By actuating various switches and relays located on this board, the CPU controls the
status of other key components. The relay board receives instructions in the form of
digital signals over the I
various switches and relays appropriately.
The two heaters attached to the sample chamber housing and the GFC Wheel motor are
controlled by solid state relays located on the relay board.
The GFC Wheel heater is simply turned on or off, however control of the bench heater
also includes circuitry that selects which one of its two separate heating elements is
activated depending on whether the instrument is running on 100 VAC, 115 VAC or 230
VAC line power.
The GFC Wheel operates from a AC voltage supplied by a multi-input transformer
located on the relay board. The step-down ratio of this transformer is controlled by
factory-installed jumpers to adjust for 100 VAC, 115 VAC or 230 VAC line power.
Other circuitry slightly alters the phase of the AC power supplied to the motor during
start up based on whether line power is 50Hz or 60 Hz.
Normally, the GFC Wheel Motor is always turning while the analyzer is on. A physical
switch located on the relay board can be used to turn the motor off for certain diagnostic
procedures.
2
C bus, interprets these digital instructions and activates its
Theory of Operation
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