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Teledyne API – Model T700 Dynamic Dilution Calibrator Principles of Operation
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10.3.5.5. External Digital I/O
The external digital I/O performs two functions.
The STATUS outputs carry logic-level (5V) signals through an optically isolated 8-pin
connector on the rear panel of the calibrator. These outputs convey on/off information
about certain calibrator conditions such as SYSTEM OK. They can be used to interface
with certain types of programmable devices.
The CONTROL outputs can be used to initiate actions by external peripheral devices in
conjunction with individual steps of a calibration sequence (see Section 4.3.2.8).
The CONTR
OL inputs can be initiated by applying 5V DC power from an external
source such as a PLC or data logger (Section 4.3.1.5). Zero and span calibrations can be
initiated by
c
ontact closures on the rear panel.
10.3.5.6. I
2
C Data Bus
I
2
C is a two-way, clocked, bi-directional, digital serial I/O bus that is used widely in
commercial and consumer electronic systems. A transceiver on the motherboard
converts data and control signals from the PC-104 bus to I
2
C. The data is then fed to the
relay board, optional analog input board and valve driver board circuitry.
10.3.5.7. Power-up Circuit
This circuit monitors the +5V power supply during calibrator start-up and sets the
analog outputs, external digital I/O ports, and I
2
C circuitry to specific values until the
CPU boots and the instrument software can establish control.
10.3.6. INPUT GAS PRESSURE SENSOR PCA
This PCA, physically located to the just to the left of the MFCs, houses two pressure
sensors that measure the pressure of the incoming diluent gas (zero air) and calibration
gases relative to ambient pressure. Pneumatically, both sensors measure their respective
gases just upstream from the associated MFC.
This data is used in calculating the concentration of calibration mixtures.
The following TEST functions are viewable from the instrument’s front panel:
CALPRESS - the pressure of the selected calibration gas input reported in PSIG.
DILPRESS - the pressure of the diluent gas (zero air) input also reported in PSIG.
06873B DCN6388