COSA Xentaur Hygrocontrol Type 83 - Manual (Page 6)

HYGROCONTROL Manual for Type 83 Page - 5 -
electronics. We use a microprocessor for the control of all internal
functions.
The electronics for transmitting the temperature and humidity sensor
signals are built into a IP-65 housing of 80 x 160 x 55 mm. Two
different operational modes may be chosen by the user which are:
"MEASURING" and "CALIBRATION"
5.1 Operational Mode "Measuring"
After connecting the type 83 instrument to power, the transmitter is in
its normal measurement mode. The actual values of relative humidity
and temperature are taken, temperature compensated, linearised
and fed to the analogue output (the temperature may only be read
out by the HART protocol. Current taken by the transmitter
(4...20mA) is directly proportional to the measured humidity
(0...100%RH).
5.2 Operational Mode "Calibration"
5.2.1. General Notes about Calibration Standards
There is a lack of international standards for relative Humidity
calibrations, therefore, different countries may have different
methods of calibrations. Since the users of humidity meters need a
simple method to check the accuracy of their instruments, we are
supplying accessories for calibration or testing. As a standard
method we have chosen unsaturated salt solutions to create rel.
humidities of known amount - but saturated salt solutions may also
be used, to check or qualify the instrument. We control the accuracy
of our unsaturated solutions by comparison with a humidity generator
with ÖKD certification.
HYGROCONTROL instruments are to be calibrated with relative
humidity - since their sensors respond to relative, not to absolute,
humidity values.
5.2.2. How often Calibrations should be done
Before dispatch, all probes have been calibrated at 0, 20, 35, 50, 65,
80 and 95%. Changes of sensor characteristic are hard to predict, as
they depend on mechanical and chemical attack on the probe. If
stresses are high (such as temperature, vibration, dust and
aggressive media like acids, solvents and highly reactive gases), we
recommend a test within 3 to 12 months. If deviations of more than
2% are found, a recalibration makes sense.
The solutions we supply for calibration create relative humidities from
0 to 95%. We are using the following:
0% - drying granulate