5
Function
The conductivity switch LRS 1-7 in conjunction with the conductivity electrode LRG 16-9, ERL 16,
LRG 16-4 measures and monitors the electrical conductivity in conductive liquids. The conductivity
switch is designed for the connection of a conductivity electrode with a cell constant of 0.5 cm
-1
.
The integrated resistance thermometer enables the conductivity electrode LRG 16-9 to measure the
fluid temperature.
The electrical conductivity changes as the water temperature changes. To obtain readings that can be
used for comparison the measurement must be based on a standard reference temperature of 25 °C.
The water temperature is measured and the conductivity reading is automatically compensated as a
function of the adjusted temperature coefficient
T
k
(%/°C). If the temperature changes the measured
value will be linearly based on 25 °C over the whole measuring range thanks to the temperature
compensation.
An adjustable contact triggers a signal when the MAX limit is reached.
A two-point controller is integrated in the conductivity switch so that the equipment can also be used
in steam boiler installations. The two-point controller controls a continuous blowdown valve and auto-
matically closes it when the boiler is shut down.
In addition the valve can be opened and closed at certain intervalvs (purging pulses). This prevents the
continuous blowdown valve from getting stuck.
A current signal of 4 - 20 mA is available for external processing. The current signal is proportional to
the conductivity reading (as a function of the adjusted measuring range).
A short circuit or wire breakage in the conductivity electrode will trigger an error message in the
conductivity switch.
The electrical conductivity is measured in μS/cm. In some countries parts per million (ppm) is used
instead. Conversion 1 μS/cm = 0.5 ppm. The conductivity switch can be adjusted accordingly.
Explanatory Notes
Scope of supply
LRS 1-7
1 Conductivity switch LRS 1-7
1 Adhesive plate ppm
1 Installation manual
Description
The conductivity switch LRS 1-7 in conjunction with the conductivity electrode LRG 16-9 constitutes a
conductivity monitoring and control system. The electrical conductvity of
n
Condensate,
n
Boiler feedwater,
n
Cooling and cleaning water,
n
Boiler water
is monitored. In steam boiler plants the conductivity monitoring & control system is used as limit
switch and continuous blowdown controller.
