Teledyne 7120 - NDIR analyzer - Manual (Page 27)

3 Start-up and Theory of Operation Model 7120
3-4
Teledyne Analytical Instruments
Block Diagram of the Model 7120 Electronics
Thermistor
Pb/Se
Sensor
Heater
Temperature
Control
Fine
Adjustment
Coarse
Adjustment
Auto-
Range
M
U
X
A to D
Converter
Digitial to
Analog
Converter
(DAC)
0-1 V dc
Concentration
and Range
4-20 mA dc
Concentration
and Range
7110
Preamp
Auto Zero
Amplifier
Central
Processing
Unit
(CPU)
Alarm 1
Alarm 2
System
Failure
Alarm
RS-232
Range
Contacts (4)
External
Valve
Control
Remote Span
Control
Remote Zero
Control
Cal
Contact
Displays Processing
Power
Supply
A to D Conv
To CPU
Motor
IR
Source
Cell
Chopper
Wheel