41
8015383/ZUQ7/V1-3/2020-06 | SICK
O P E R A T I N G I N S T R U C T I O N S | TRANSIC151LP
Subject to change without notice
SETTING AMBIENT PARAMETERS
5
5.1.1
Pressure compensation
Setting the value of the average process pressure value compensates the measurement
error more or less to zero in the immediate vicinity of the pressure value in question.
▸
Set the average pressure as parameter for the TRANSIC151LP. Keypad,
pressure: Display and settings (APP)”, page 37
.
The graphic
“Effect of process pressure compensation”, page 40
illustrates the effect of
pressure compensation when the average process pressure is set to 1.2 bar
a
. The original
error of approximately 1% of the measured value at 1.2 bar
a
is compensated to zero.
Pressure dependency remains for other values.
Pay particular attention that setting the pressure compensation does not shift the
parabola-like curve shown in
“Effect of process pressure compensation”
along the X-axis.
This means, even with compensation activated, pressure changes of the compensation
value have a more significant effect than with 1.013 bar
a
.
5.1.2
Background gas effects
Individual absorption line widths of O
2
gas are sensitive to intermolecular collisions
between O
2
and background gas molecules. This affects the measured O
2
values. The
magnitude of this effect depends on the amount and type of background gas molecules.
TRANSIC151LP factory calibration is carried out using dry N
2
and O
2
mixtures. Humidity
and CO
2
concentrations of the calibration gases are 0%. Apart from dry N
2
, all background
gases result in a percentage measured value error for O
2
measurement.
Carbon dioxide and water vapor are the most common gases requiring compensation.
Compensation for the average water and CO
2
contents of the background gas is integrated.
The compensation is based on manual user settings for the values for the water and CO
2
content of the background gas in the device. The water content is expressed in terms of
absolute humidity in g/m
3
H
2
see “Humidity Conversion Table”,
. The conversion formulas can be found in Section
.
NOTE:
To disable pressure compensation, reset the average process pressure value to the
standard ambient air pressure of 1.013 bar
a
. The magnitude of pressure compensation
is zero with this setting.
The allowable pressure range for compensation is 0.800 ... 1.400 bar
a
.
All gases, apart from N
2
, influence the measured value.
Contact SICK Customer Service for information on the influence of further background
gases.
NOTE:
Adapting compensation values to ambient conditions
●
When humidity and CO
2
compensation is/are activated, and when the ambient
conditions deviate from the ambient conditions during adjustment:
1
Set the water and CO
2
content according to the adjustment environment.
2
These settings then have to be changed back to represent those of the operating
conditions when the TRANSIC151LP is reinstalled in the process.
