Ametek 888 User Manual

Calculations | Appendix B-1
H
2
S AND SO
2
CALCULATIONS
Concentration Measurement
There are four detectors and bandpass filters used to measure the concen-
tration of H
2
S and SO
2
. The signal from each of the detectors is measured
by individual analog-to-digital converters and those values are used to
calculate concentration.
Absorbance Calculation
The absorbance is calculated for each channel using the stored values
from the last zero calibration. The absorbance for each detector is calcu-
lated by the formula:
ABS = log
AD
zero
AD
measured
( )
AD
zero
Stored analog-to-digital converter reading
AD
measured
Current value from the converter.
If span correction is enabled, each absorbance value is then multiplied by
its corresponding span factor.
One of the four detector filters is at a wavelength not absorbed by either
H
2
S or SO
2
. That measurement is used as a reference for the subsequent
calculations. The absorbance of the reference detector is subtracted from
each of the remaining three detector absorbance values. A polynomial is
applied to these differential absorbance values to calculate concentration.
There is a separate set of polynomial coefficients for H
2
S and SO
2
. The
delta terms in the equation are the differences between a measurement
absorbance and the reference absorbance.
[conc]x = C
0
+ C
1
* ∆
1
+ C
2
* ∆
1
2
+ C
3
* ∆
2
+ C
4
* ∆
2
2
+ C
5
* ∆
3
+ C
6
* ∆
3
2

Ametek 888 Specifications

General

Brand	Ametek
Model	888
Category	Measuring Instruments
Language	English