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TECHNOLOGIES LTD
Combi / XDI-XDIwin Toxic/Oxygen Sensor
4 / 3 / 2 wire sensor
Set up procedure:
204D1C Issue N.v2
NEW SENSORS ARE SUPPLIED READY TO CONNECT TO A SYSTEM WITH ALL JUMPERS INSERTED.
THIS PROCEDURE SHOWS HOW TO RECALIBRATE AS PART OF ROUTINE MAINTENANCE OR CELL
REPLACEMENT.
The first part is to set up the 4-20mA section which is produced by the CELL circuit. Note some cells take time to
stabilise. If used as 2 wire then only steps 1 to 5 are required.
1. Connect the cell to terminal J2 and use +24V, 0V and 4~20mA connections on terminal J10 for 3wire (or +24V
and 4~20mA for 2wire)
2. Measure voltage across test pins AG to Vo and adjust reading to zero mV using RV1 Offset pot
3. Measure the output current mV=mA at test pins TP1/TP2 and adjust reading to 4mV using RV3 4mA pot
4. Apply span gas to cell and adjust RV2 20mA pot to give correct mV reading at test pins TP1/TP2. NOTE: at
50% span gas, the mV reading at TP1/TP2 should be 12mV and the voltage across test pins AG and Vo
should not exceed 1 volt so that 100% of range is achievable.
5. Remove the span gas and re-adjust 4mA pot RV3 to 4mV IF REQUIRED.
4 Wire with processor communications via CAN bus
6. With power applied ensure that MPU led is flashing and the CAN led is on or flashing.
7. Connect RS232 pod to J3 connector and to a PC running HyperTerminal at 4800 baud.
8. The terminal output screen shows continuous data output and allows input from the PC keyboard.
Pressing ‘C’ enters calibration mode
a. Press ‘SHIFT $’ to initialise the sensor and reset to default “Flam 100% LEL” setting.
b. Then press ‘G’ to change the gas type to match the cell being used.
NOTE: the range of the new gas has a default value but can be changed by pressing ‘R’.
c. Press ‘A’ to change the address of this sensor if required
d. Press ‘N’ to select the number of decimal places to 1 or 2, (ie: dp=1 or dp=2)
e. With no gas applied and 4mV measured at test pins TP8/TP9 press ‘Z’ to zero the gas reading.
f. Then apply span gas and press ’S’ to enter span mode. The reading can be made HIGHER by pressing ‘H’
or lower by pressing ‘L’
g. Pressing ‘SPACE BAR’ will exit the span mode
h. Pressing ‘X’ will exit the calibration mode.
Note:
Oxygen cells only have two wires and connect to P+ and Y on terminal J2. To adjust for “zero” it is
normal practice to disconnect 1 wire from the cell and adjust the 4mA pot RV3 to get a 4mV reading across
test pins TP8/TP9 for 3 wire sensor or test pins TP1/TP2 for 2 wire sensor. When the cell is reconnected in air
at 20.9% oxygen the span can be adjusted for 17.3mV reading across the same test pins.
If an LCD option is fitted then calibration and other settings using magnets instead of a PC can be achieved as
follows on next page.
D
a
t
a
S
heet
ref C894
