6.3.4 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 sensor list, manual 3. ´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:
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 ´Measurement correction´ menu, and
entering the temperature:
Entering the compensation temperature in the function:
TempComp: 31.2
If a temperature sensor is available and continuously measured, the
temperature will be continuously indicated. This allows to display
both measured values for any double sensors.
6.3.5 Atmospheric Pressure Compensation
Some measuring variables depend on the environmental atmospheric pressure
(see 9.9 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%)
O
2
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
corresponding height above sea level. It can either be programmed or
measured with a reference sensor (see manual 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: 1013mb
With each reset the atmospheric pressure is set to 1013mb. It can be set to the
current value by the usual data entry (see 5.5). 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.
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ALMEMO
®
2590-9
Displaying a Measuring Point
