PRO902C MANUAL
T
FS
Rev 6.0
August 16, 2007
3-10
In this example, 17.376 mA equals 20.9% oxygen:
( 0.836 * 16) + 4 = 17.376 mADC output
Four (4) mA has been set to equal 0% oxygen and 20 mA has been set to equal 25% oxygen
(full-scale). Therefore, 12 mA is the midpoint between 4 and 20 mA and equals 12.5%
oxygen, which is half the full-scale value (25%) in our example.
3.6
City Technology O
2
sensor alignment
NOTE: ALLOW ONE (1) HOUR MINIMUM INITIAL RUN TIME ON CELL BEFORE
PROCEEDING.
A)
At the dilution probe conditioning assembly, locate the O
2
cell holder and remove the
two wire jack attached to the red and black leads. Attach a DC volt meter to the leads.
B)
Locate the two switches on the right-hand side wall of the enclosure. Select the O
2
zero request position. In this position, the cell output will drop to 0.0 mV DC (only if there
are no leaks in the system). Let the system run on O
2
zero gas for approximately 5 minutes or
until the cell output stabilizes.
C)
Verify that the cell's output is acceptable (0.0 mV DC), then disconnect the DC volt
meter and plug the jack back into its socket. Attach a DC ammeter in series with terminal
(22) of the valve controller watchdog module, VCM1.
D)
Verify that the O2 zero switch is in the “ON” position and that the cell’s output has
stabilized. Adjust the output, if required, to 4 mADC using the zero potentiometer.
E)
Turn the O
2
zero request switch back to the "Auto" position and place the O
2
span
request switch to the "On" position.
The span value of the 4-20 mADC output is calculated using the following formula:
span gas concentration
------------------------------ = % of full scale
full scale concentration
( % of Full Scale * 16) + 4 = mADC output
Example:
Summary of Contents for PRO902C
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