Error Compensation - CODEL Energy Tech 401 Installation, Operation And Maintenance Manual

EnergyTech 401
Operating and Maintenance Manual
2.2.2

Error Compensation

Page: 18
The accurate determination of gas concentration depends upon the
measurement of the radiation levels received by the detectors. Any error in that
measurement caused by detector drift will produce errors in the determination of
the gas level. In order to maintain accuracy, it is necessary to be able to
compensate for such drifts. A technique of continuous calibration adjustment is
used.
The operating cycle of the instrument is in two parts. First, measurements are
obtained from the two detector outputs D1 and D2.
containing pure CO is then positioned in the sight path and the two detector
outputs are measured again to give readings E1 and E2.
From the basic scale shape equation :
Y =
and from the calibration equation
Yo =
or K =
thus substituting in the scale shape equation
Y =
The two ratios E1/D1 and E2/D2, being derived each from one detector, are
independent of any detector drift, thus making the instrument output
independent of any drift or change in detector gain characteristic.
This operating routine, giving measurements first of D1 and D2 and then, with the
calibration cell in position, of E1 and E2, is repeated continuously and provides an
effective continuous calibration update to enable accuracy to be maintained at all
times.
CODEL
Monitoring Solutions
The calibration cell
G - K. D2/D1
G - K. E2/E1 ............(at zero Yo = Set Cal Value)
(G - Yo). E1/E2
G - (G - Yo). E1/E2. D2/D1