Rotronic Pt 100 RTD User Manual

1. Procedures:
1.1 General recommendations
Relative humidity is extremely dependent on temperature. Proper measurement of relative
humidity requires that the probe and its sensors are at exactly the temperature of the
environment to be measured. Because of this, the location you choose to install the probe can
have a significant effect on the performance of the instrument. The following guidelines should
guarantee good instrument performance:
a) Select a representative location: install the probe where humidity, temperature and pressure
conditions are equal to the environment to be measured.
b) Provide good air movement at the probe: air velocity of at least 1 meter/second
facilitates adaptation of the probe to changing temperature.
c) Avoid the following:
Close proximity of the probe to a heating element, a cooling coil, a cold or hot wall, direct
exposure to sun rays, etc.
Close proximity of the probe to a steam injector, humidifier, direct exposure to precipitation
etc., unstable pressure conditions resulting from excessive air turbulence.
1.2 Sources of errors
Measurement values may be affected by :
- Temperature faults:
Too short adaptation time, cold walls, heating elements, sun radiation etc. Even the
body-radiation of man may affect the measurement. When calibrating, keep as much
distance as possible.
- Humidity faults
Humidity errors due to sprayed steam or water, dripping water, attempts to measure non-
hygroscopic substances. The reproducibility and long-term stability are not influenced even if
the sensor was exposed to high humidity or saturation with water vapour condensation.
1.3 Periodic probe calibration
The Pt 100 RTD temperature sensor as well as the electronics are very stable and normally do
not have to be adjusted after the factory-calibration.
The long-term stability of the ROTRONIC Hygromer sensors is typically better than
1 %rh per year. For maximum accuracy, we recommend to calibrate the probes once or twice a
year. In applications where the sensor is exposed to pollutants, it may be necessary to calibrate
or adjust more often. The calibration may be performed by the user on-site or in the
laboratory/workshop.
For routine calibrations, the probe should be checked at one point, preferably at the
prevailing values. For applications in the ambient, this would normally be at 50 %rh.
In industrial and pharmaceutical applications, where the accuracy must be higher, we
recommend to calibrate the probes at 3 points: (in this sequence): 35, 80, 10 %rh.
If measurements are performed at very low humidity, we recommend to calibrate/ adjust
also at 0 (0.5) %rh.
Note: The electronics of the Rotronic transmitters usually does not require any field
maintenance. However, the probe itself should be calibrated at least once per year, in order to
maintain it’s high quality. For details of calibration, see users manual (full version). It may be
downloaded from the internet.
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Rotronic Pt 100 RTD Specifications

General

Brand	Rotronic
Model	Pt 100 RTD
Category	Measuring Instruments
Language	English