CAUTION: There are live circuits inside the controller even when the power switch is in the
OFF position! Servicing and troubleshooting the controller must be performed by Qualified
Service Personnel.
5
Section 2 (B):
WEL Transmitter Housing
+ Electrode Reading is Stuck on
one Value or Reading Erratically
Note: This section is applicable to W600 and W900 controllers (not applicable to W100
controllers).
The WEL Transmitter housings are:
For use with ORP electrodes (cartridges), with a 4-20 mA range scaled to -500 to 1000 mV.
The other has automatic temperature compensation (measured by an RTD) for use with pH
electrodes (cartridges), with a 4-20 mA range scaled to 0 to 14 pH standard units.
Note: The WEL Transmitter H pH Electrode will output a 4-20mA signal
only, there will not be a separate temperature reading sent to the controller.
Automatic temperature compensation takes place inside the WEL Transmitter
Housing.
The following are normal (expected) readings when the controller electrode input is programmed as pH,
and the following configurations are in place:
With nothing connected to the analog input terminals in the controller, the reading should be
about 0 mV (7 pH).
With just the WEL Transmitter housing wired into the analog input terminals in the controller (but
no electrode installed), the reading should float (vary low to high to low to high, etc.).
With the WEL Transmitter housing wired into the analog input terminals in the controller, and the
electrode threaded into the housing, if the RTD (automatic temperature compensation) fails in
the open position (wires somehow disconnected inside the housing) the reading should be stuck
at 0mV (7pH).
With the WEL Transmitter housing wired into the analog input terminals in the controller, and the
electrode threaded into the housing, if the RTD (automatic temperature compensation) fails in
the closed position (wires somehow shorted inside the housing) the reading should float (vary
low to high to low to high, etc.).
With the WEL Transmitter housing wired into the analog input terminals in the controller, and the
electrode threaded into the housing, if the glass on the end of the electrode breaks, the reading
should be a constant 12.0 mA (7pH).
