Справочник Пользователя для Teledyne gfc 7000ta

 

Teledyne Analytical Instruments 

207 

 

Special circuitry on the relay board monitors the activity on the 

I

2

C

 bus and drives LED D1.  Should this 

LED ever stay ON or OFF for 30 seconds, the watchdog circuit will automatically shut of all valves as well 
as turn off the IR Source and all heaters.  The GFC wheel motor will still be running as will the Sample 
Pump, which is not controlled by the relay board. 

This printed circuit assembly provides a multitude of functions including, A/D conversion, digital 
input/output, PC-104 to I2C 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 (e.g.  BOX TEMP, CO2 
MEAS

, CO2 REF, etc.) and then coverts the selected voltage into a digital word.   

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.