4
Important notes
Intended use
Use conductivity transmitters LRGT 16-1, LRGT 16-2 and LRGT 17-1 only for measuring electrical
conductivity in liquids.
Conductivity transmitters LRGT 16-1 / LRGT 16-2/17-1 can be used as conductivity limiters or
continuous blowdown controllers in steam boilers in combination with the following equipment:
Conductivity controller LRR 1-51
Conductivity controller LRR 1-53
Industrial controller KS 90-1
To guarantee trouble-free operation, observe the requirements made on water as specified
in the pertinent TRD and EN regulations.
The equipment may only be used within the admissible pressure and temperature ratings.
Function
The compact conductivity transmitters LRGT 16-1, LRGT 16-2, LRGT 17-1 consist of a conductivity
electrode, a temperature sensor for detecting the liquid temperature, and an electronic circuit board
incorporated in the terminal box.
Conductivity transmitters LRGT 16-1, LRGT 17-1 use the conductometric measuring method with
two measuring electrodes, while transmitter LRGT 16-2 uses the conductometric technique with four
measuring electrodes. The equipment measures the electrical conductivity of electrically conductive
fluids (TDS = Total Dissolved Solids content), and provides a 4-20 mA measuring current as a function
of the detected conductivity value.
LRGT 16-1, LRGT 17-1
A measuring current of variable frequency passes through the fluid, creating a potential gradient
between the measuring electrode and the measuring tube, which is then used as measuring voltage U
U
.
LRGT 16-2
The conductivity electrode consists of two current and two voltage electrodes. The current electrodes
direct the measuring current U
I
into the fluid at a fixed frequency, thereby creating a potential gradi-
ent between these electrodes. This potential gradient is then picked up by the voltage electrodes and
evaluated as measuring voltage U
U
.
LRGT 16-1, LRGT 17-1 and LRGT 16-2
The electrical conductivity is a function of the temperature. In order to base the measured values on a
reference temperature, a resistance thermometer integrated in the electrode therefore measures the
fluid temperature.
The electrical conductivity is calculated from measuring voltages U
U
and U
I
and – as a function of the
adjusted temperature coefficient T
k
– based linearly on the reference temperature of 25°C. Once it has
been converted into a current signal proportional to the conductivity, an output current of 4-20 mA is
available for external further processing.
The cables leading to the measuring electrode, the measuring tube and the resistance thermometer
are monitored and checked for open and short circuit. In addition, the circuit board is protected against
excess temperatures in the terminal box. In the event of a malfunction, the LEDs light up or flash and
the current signal is set to 0 or 0.5 mA.
The code switch enables configuration of the transmitter, the adaptation of the cell constant and activa-
tion of a function test. Electrical conductivity is measured in µS/cm. In some countries, ppm (parts per
million) is used instead. 1 µS/cm = 0.5 ppm.
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