Section 4
4-10 Calibration
command sequence, and the user can get the analyzer back “on scale”
through software if the zero and/or span has gone beyond the range of the
potentiometer.
The zero and span parameters initially default to these values:
H2 Zero = 0.0 (mV offset)
H2 Span = 1.0 (dimensionless)
C2 Zero = 0.0 (mV offset)
C2 Span = 1.0 (dimensionless)
When these default values are in effect, no software zero or span adjustments
are performed.
When the H2 Zero and H2 Span values are changed, the mV signal normally
used in the calculation of H
2
O concentration (FCT 31) is transformed
according to
H
2
O mV
new
= (H2 Span) × (mV - [H2 Zero]).
When the C2 Zero and C2 Span values are changed, the mV signal normally
used in the calculation of CO
2
concentration (FCT 21) is transformed
according to
CO
2
mV
new
= (C2 Span) × (mV - [C2 Zero]).
The values of CO
2
mV
new
and H
2
O mV
new
are used by the calibration
polynomials to compute concentration, but do not change the raw CO
2
mV
signal displayed at channel 21, or the raw H
2
O mV signal displayed at
channel 31, or the output (RS-232C) values of either.
The values of H2 Zero and H2 Span, and C2 Zero and C2 Span can be
entered via the keypad at FCT 08, or by sending a remote command
sequence. When sending a remote command, you have the option of
entering the Zero and Span values, or allowing the analyzer software to
calculate the values for you. The following examples demonstrate how you
can calibrate your LI-6262 in software for both absolute and differential
measurements.
Remote Commands
The remote command sequence for the CO
2
software zero and span is
To Next Page
