14
7.2 Calibrating the ammonia sensor
General information
The slope of the sensors varies somewhat from instance to instance
and also changes during operation (caused by deposits such as
lime, or by wear). This changes the output signal of the sensor.
The software of JUMO dTRANS pH 02 and JUMO AQUIS 500 pH
transmitters is specifically geared to coolant monitoring. They use a
typical, concentration-dependent characteristic line. The individual
properties of the sensor are only taken into account here by
offsetting the zero point. This considerably reduces the effort
required for calibration.
Ammonia calculation
The ammonia sensor output signal follows a straight characteristic
line up to voltage U
1
(default = 84 mV). Above U
1
, the characteristic
line will be curved (see diagram on Page 9).
Lower detection limit U
0
U
0
is the voltage supplied by the ammonia sensor in an ammonia-
free process medium.
The default setting for U
0
is 138 mV.
One-point calibration
With one-point calibration, voltage U
0
is determined (in the
ammonia-free process medium).
Requirement:
The process medium must be free from ammonia.
✱
Immerse the ammonia sensor in the process medium.
✱
Start one-point calibration on the JUMO transmitter.
✱
Wait until the voltage shown on the JUMO transmitter has
stabilized.
Please do not make any changes by pressing the
or
keys!
✱
End calibration by pressing the
key.
The JUMO transmitter shows 0.0 ppm.
PGM