Ahlborn ALMEMO 2890-9, Operating Instructions Manual

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10. Measuring using Measuring-Menus
10.2.5 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 temper-
ature sensor and the instrument will automatically perform a temperature com-
pensation (s. 11.3.9 measuring range list ´w. PC´). 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:
e.g. error per 10 °C: Compensation range: Sensor:
Dyn.press: approx. 1.6% -50 to 700 °C NiCr-Ni
pH probe: approx. 3.3% 0 to 100 °C Ntc or Pt100
The temperature compensation can either be performed automatically using
the reference channel and external temperature sensors or manually by using
the function
Temp Comp
e.g. in the menu
Meas.Correction
and entering the
temperature:
Entering the compensation temperature in the function
:
Temp Comp: 31.2°C
10.2.6 Atmospheric Pressure Compensation
Some measuring variables depend on the environmental atmospheric pressure
(s. 11.3.9 measuring range list ´w. PC´). As a result, higher deviations from the
normal pressure of 1013mbar can cause corresponding measuring errors:
e.g. error per 100 mbar: Compensation range:
Rel. humidity psychrometer approx. 2% 500 to 1500 mbar
Mixture ratio, cap. approx. 10% vapour pressure VP to 8 bar
Dynamic pressure approx. 5% 800 to 1250 mbar (error < 2%)
O2 saturation approx. 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 correspond-
ing height above sea level. It can either be programmed (s. 11.5.6) or mea-
sured with a reference sensor (reference sensor marked with comment ´*P´ s.
man. 6.7.2).
The function
Atmospheric Pressure
can be integrated into any user menu or
be set in the standard menu Device Configuration :
Entering the atm. pressure in function ´Atm. Press.´:
AtmPress: 1013. mb
With each reset the atmospheric pressure is set to 1013mb. It can be set to the
current value by the usual data entry (s. 9.5). If it is measured, the measured
value will be displayed.
Please note that the last measured value will be retained when a
reference sensor is being disconnected.
28 ALMEMO ® 2890-9
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