Teledyne API T802 Paramagnetic O2 Analyzer Operation Manual Principles of Operation

227

Finally, the CPU issues commands via a series of relays and switches (also over

the I2C bus) located on a separate printed circuit assembly to control the function

of key electromechanical devices such as heaters..

Flow/Pressure Sensor PCA
Optional CO2
Sensor Heater
Analog Outputs
Aout 1
Aout 4
Analog Outputs
(D/A) External Digital I/O
Power Up
Circuit
PC 104 Bus
PC 104
CPU Card
Disk on
Module
Flash
Chip
Aout 3
Aout 2
TEST CHANNEL OUTPUT
Status
Outputs
1 -8
Control
Outputs
1 –6
Optional Current LoopOutputs
CPU
Status
LED
I2C Bus
O2Cell
Heater
Thermistor Interface
Box
Temperature
Sample Flow
Sensor
A/D
Converter
RELAY PCA
I2C
Status
LED
O2Range 2
O2Range 1
MOTHERBOARD
Sample Pressure
Sensor
Sensor Inputs
CO2(optional)
O2Sensor
Optional CO2
Sensor
Internal
Digital I/O
O2
Concentration
O2Sensor
Temperature
CO2Sensor
Temperature
(Optionl)
BOX
Temperature
COM2
Female
RS232
Male Ethernet
USB COM
port
ANALOG
IN
(
I
2
C Bus
)
COM1(RS-232 only)
COM2 (RS-232 or RS-485)
or USB
Touchscreen
Dis
p
la
y
LVDS
transmitter
board
USB

Figure 12-7: T802 Electronic Block Diagram

12.5.2. ELECTRONIC OPERATION OF THE CO2 SENSOR

The CO2 PCA is powered by 12 VDC from the analyzer via the relay card, which

outputs a 0-5 VDC analog signal to the analyzer’s CPU via the motherboard that

corresponds to the concentration of CO2 measured by the probe.