Teledyne gfc 7000ta Relay Board, Dark Calibration Switch, Electric Test Switch, Heater Control

Theory of Operation Model GFC7000TA Carbon Dioxide Analyzer

9.3.4.4. Photo-Detector Temperature Control

The synch/demod board also contains circuitry that controls the IR photo-detector’s thermoelectric coolers. A drive voltage, PHT DRIVE, is supplied to the coolers by the synch/demod board which is adjusted by the synch/demod board based on a return signal called TEC control which alerts informs the synch/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 front panel. Press <TST or TST> until it appears on the display.

9.3.4.5. Dark Calibration Switch

This switch initiates the Dark Calibration procedure. When initiated by the user (See Section 6.13.6 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 synch/demod board circuitry.

9.3.4.6. Electric Test Switch

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 6.13.5 for more details).

9.3.5. Relay Board

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 I2C bus, interprets these digital instructions and activates its various switches and relays appropriately.

9.3.5.1. Heater Control

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.

9.3.5.2. GFC Wheel Motor Control

The GFC wheel operates from an 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.

Teledyne Analytical Instruments 205