used for all thermocouple types; however, they require two measuring chan-
nels. ´
#J
´ is programmed in the comments; this ensures that the temperature
sensor integrated in the connector is used for cold junction compensation.
6.2.5 Atmospheric pressure compensation
Some measured variables depend on the ambient atmospheric pressure (see
Section 7.7, measuring range list ´with PC´) with the effect that pronounced de-
viations from normal pressure (1013 mbar) may lead to measuring errors.
e.g. error per 100 mbar:
Compensation range:
Rel. humidity psychrometer approx. 2%
500 to 1500 mbar
Mixture ratio, capacitive
approx. 10 %
Vapor pressure VP up to 8 bar
Dynamic pressure
approx. 5%
800 to 1250 mbar (error < 2%)
O2 saturation
approx. 10%
500 to 1500 mbar
Account should be taken, therefore, especially when working at significant
heights above sea level, of the atmospheric pressure (approx. -11 mbar per
100 meters above mean sea level MSL). This can either be programmed or
measured directly with a sensor (see Manual, Section 6.7.2).
The ATMOSPHERIC PRESSURE function
´mb
´ is only activated as and when
necessary for sensors of the types mentioned above (see Section 5.2) by hol-
ding down the
FUNCTION
key the first time it is pressed.
ATMOSPHERIC PRESSURE function ´
mb
´
Select by key ...
and enter mba s. 5.4
FUNCTION
1 0 1 3
mb
With each reset the atmospheric pressure is set to 1013 mbar. It can be set to
the current value by means of the usual data entry process; (see Section 5.4).
6.2.6 Temperature compensation
Sensors whose measured values depend heavily on the temperature of the
measuring medium usually incorporate their own temperature sensor; such de-
vices perform temperature compensation automatically; (see Section 6.2, mea-
suring range list ´with TC´). However, dynamic pressure probes and pH probes
are also available without their own temperature sensor. If the temperature of
the medium deviates from 25 °C the following measuring errors may occur :
e.g. error per 10 °C :
Compensation range :
Sensor :
Dynamic pressure app. 1.6%
-50 to +700 °C
NiCr-Ni
pH probe approx. 3.3%
0 to +100 °C
Ntc or Pt100
Temperature compensation can also be performed using the reference channel
and external temperature sensors; or it can be performed manually by entering
the temperature in the ´
TC
´ function (reference channel = measuring channel).
TEMPERATURE COMPENSATION function ´
TC
´
28
ALMEMO
2390-5
Measuring operations
Содержание ALMEMO 2390-5
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