GE moisture.IQ, User Manual

Page: 102 / 182

Chapter 7. Maintenance
90 moisture.IQ User’s Manual
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
PPM O2
content of the span gas and the measured
μ A value
instead of using the following procedure.
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:
BHGE 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
2
in N
2
for a 0-100 PPM O
2
sensor).
1. Initiate flow of the calibration gas through the oxygen cell.
2. Read the PPM
v
value. If it is correct, your oxygen cell does not need calibration. If the reading is
incorrect, you must calculate the new span reading (x) from the following equation:
where OX
c
= Correct PPMv for the calibration gas
OX
0
= Zero value in PPMv*
OX
1
= Span value in PPMv*
IO
c
= Actual reading for the calibration gas in μA
IO
0
= Zero value in μA*
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
c
= 75 PPMv = Correct PPM
v
for the calibration gas
OX
0
= 0.050 PPM
v
= Zero value in PPM
v
OX
1
= 100 PPMv = Span value in PPMv
IO
c
= 290 μA = Actual reading for the calibration gas
IO
0
= 0.4238 μA = Zero value
Then,
The new
span value (x)
is 100 PPMv

387 μA. Enter the new value as described in “Calibrating the Probes” on
page 66 .
x IO
c
OX
1
OX
c
–
 
IO
c
IO
0
–
 
OX
c
OX
0
–
 
--------------------------------------------------------------- + =
290
100 75 –
 
290 0.4238 –
 
75 0.05 –
 
-------------------------------------------------------------- + x =