7.1.8 Atmospheric Pressure Compensation
Some measuring variables depend on the environmental atmospheric pressure
(see 6.2 measuring range list ´with PC´). As a result, higher deviations from the
normal pressure of 1013mbar can cause corresponding measuring errors:
For example, error per 100 mbar:
Compensation Range:
Rel. humidity, psychrometer
ca. 2%
500 to 1500 mbar
Mixture ratio, cap.
ca. 10 %
vapour pressure VP to 8 bar
Dynamic pressure
ca. 5%
800 to 1250 mbar (error < 2%)
O
2
saturation
ca. 10%
500 to 1500 mbar
Therefore, the atmospheric pressure should be considered (approx.
-11mb/100m over mean sea level, MSL) especially during use in a
corresponding height above sea level. It can either be programmed or
measured with a sensor (see manual 6.7.2).
Function ATMOSPHERIC PRESSURE ´
mb
´
Select by using the key
... Input mbar, see 5.4
F2
1
0 1
3
m
b
With each reset the atmospheric pressure is set to 1013mb. It can be set to the
actual value by the usual data entry (see 5.4).
7.1.9 Temperature Compensation
Sensors with measured values that are strongly depending on the temperature
of the measuring medium are, in most cases, equipped with a specific
temperature sensor and the instrument will automatically perform a
temperature compensation (see measuring range list 6.2 ´w. TC´). However,
dynamic pressure probes and pH probes are also available without a
temperature sensor. If the temperature of the medium deviates from 25°C the
following measuring errors must be considered:
For example, error per 10 °C:
Compensation Range:
Dynamic pressure
ca. 1.6%
-50 to 700 °C
pH probe
ca. 3.3%
0 to 100 °C
The temperature compensation can also be performed with external
temperature sensors by using the reference channel, or within the function
´
TC
´
by entering the temperature manually:
Function TEMPERATURE COMPENSATION ´
TC
´
Select by using the key
... Input °C, see 5.4
F2
1:
1
8
0
.
0
T
C
Display when autom. temp. compensation is selected:
1:
A
u
t
o
T
C
34
ALMEMO
2290-2/3
Continuous Measurement of a Measuring Point
Summary of Contents for ALMEMO 2290-2/3
Page 44: ...44 ALMEMO 2290 2 3 Appendix ...
