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Principles of Operation
8.5.8. STATUS LEDS & WATCH DOG CIRCUITRY
8.5.8.1. Watchdog Indicator (D1)
T
he most important of the status LED's on the relay board is the red I
directly analyzer's CPU over the I
this LED ever stay ON or OFF for 30 seconds, indicating that the CPU or I
Watchdog Circuit automatically shuts all valves and turn off all heaters.
8.5.9. MOTHERBOARD
8.5.9.1. A to D Conversion
298
Thirteen LEDs are located on the analyzer's relay board to indicate the status of the
analyzer's heating zones and valves as well as a general operating watchdog indicator.
Table 7-2 shows the states of these LEDs and their respective functionality.
Figure 8-22:
Status LED Locations – Relay PCA
2
C bus. Special circuitry on the relay PCA watches the status of D1. Should
This is the largest electronic assembly in the analyzer and is mounted to the rear panel as
the base for the CPU board and all I/O connectors. This printed circuit assembly provides
a multitude of functions including A/D conversion, digital input/output, PC-104 to I
translation, temperature sensor signal processing and is a pass through for the RS-232 and
RS-485 signals.
Analog signals, such as the voltages received from the analyzer's various sensors, are
converted into digital signals that the CPU can understand and manipulate by the analog
to digital converter (A/D).Under the control of the CPU, this functional block selects a
particular signal input and then coverts the selected voltage into a digital word.
Teledyne API - Model T200H/T200M Operation Manual
2
C Bus watch-dog LED. It is controlled
2
C bus has stopped functioning, this
2
C
07270D DCN7141
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