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Chapter 7. Maintenance
7.3.2 Checking the Oxygen Cell Calibration
Note:
If your range of measurement is significantly below the span gas you are using, you may elect to input the
O2
content of the span gas and the measured
To perform this calibration check you must have a calibration gas with a known PPMv value and a sample system with
a calibration gas inlet valve. Proceed as follows:
Note: GE recommends a span calibration gas be 80-100% of the span of the sensor's overall range in a background
of nitrogen (e.g., 80-100 PPM O
1. Initiate flow of the calibration gas through the oxygen cell.
2. Read the PPM
v
must calculate the new span reading (x) from the following equation:
where
OX
= Correct PPMv for the calibration gas
c
OX
= Zero value in PPMv*
0
OX
= Span value in PPMv*
1
IO
= Actual reading for the calibration gas in µA
c
IO
= Zero value in µA*
0
x = New span reading in µA
*See the Calibration Data Sheet for the oxygen cell to obtain the necessary zero and span values.
For example, if the calibration data for your cell is as follows:
OX
= 75 PPMv = Correct PPM
c
OX
= 0.050 PPM
= Zero value in PPM
0
v
OX
= 100 PPMv = Span value in PPMv
1
IO
= 290 µA = Actual reading for the calibration gas
c
IO
= 0.4238 µA = Zero value
0
Then,
span value (x)
The new
is 100 PPMv
page 64.
88
in N
2
2
value. If it is correct, your oxygen cell does not need calibration. If the reading is incorrect, you
x
=
IO
for the calibration gas
v
v
(
------------------------------------------------------------- -
290
+
≅
387 µA. Enter the new value as described in "Calibrating the Probes" on
µA value
instead of using the following procedure.
for a 0-100 PPM O
sensor).
2
(
) IO
(
OX
–
OX
–
1
c
c
-------------------------------------------------------------- -
+
(
)
c
OX
–
OX
c
0
) 290 0.4238
(
100 75
–
–
(
)
75 0.05
–
)
IO
0
)
=
x
PPM
moisture.IQ User's Guide
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