Automatikprodukter
Ammonia detector - Manual
NH3/ENH3
April.10
Electrochemical Transmitter
Electrochemical Ammonia Transmitter
1
Intended for Use
The NH
3
analog transmitter with digital processing of the measured values and temperature compensation is used
to detect leakages of ammonia in the ambient air.
The sites intended for use are all areas being directly connected to the public low voltage supply, e.g. domestic,
commercial and industrial ranges as well as small enterprises (acc. to EN 50 082).
The NH
3
analog transmitter is not suitable for the application in areas exposed to explosive hazards.
2
Functional Description
2.1
Control Mode
In addition to the analog output the transmitter is equipped with a serial interface RS-485 for the connection to the
GCD-05 system.
Analog mode:
The analog output can be selected as current signal with (0)4-20 mA or as voltage signal (0)2-10 V.
In the 4-20 mA mode and without any supplementary options, the NH3/ENH3 also works in the 2-wire technique.
DGC-05_Bus mode:
The transmitter can be connected to the GCD-05 system via the RS-485 interface.
In this mode there is an analog input for the connection of an additional 4-20 mA transmitter.
The two measuring values are transmitted via the RS-485 interface to the gas controller.
The cable topology for the RS-485 bus can be taken from the ”Guidelines for wiring and commissioning of the
GCD-05 hardware”.
The two control modes are available in parallel.
2.2
Sensor
The sensor portion of the transmitter is a sealed micro-fuel cell with three electrodes, sensing, counter and reference.
The ambient air enters the cell through a diffusion barrier into the liquid electrolyte of the sensor.
The chemical process of the measurement is one of reduction where one molecule of the target gas is exchanged
for one molecule of oxygen.
The reaction drives the oxygen molecule to the counter electrode, generating a DC microampere signal between the
sensing and counter electrodes.
This signal is linear to the volume concentration of the sensed gas.
The signal is evaluated by the connected amplifier and transformed into a linear output signal.
Electrochemical processes always lead by-and-by to a loss of sensitivity.
Therefore regular calibration of the zero-point and of the gain is necessary. See also section 6.
Caution:
Avoid any force (e.g. by thumb) on the sensor element during operation or installation.
This could destroy the sensor element.
There is a small quantity of corrosive liquid in the sensor element.
If in case of damage persons or objects encounter the liquid, you have to clean the affected areas as fast and carefully
as possible with tap water.
Out of use sensors must be disposed in the same way as batteries.
