72-910-16 Rev. N
Page 4 of 43
1.
INTRODUCTION
The
MicroVision
microprocessor based cooling tower controller has been designed to
monitor and control Total Dissolved Solids (TDS) in terms of electrical conductivity
measured in micro Siemens per centimeter (uS/cm). A set point of the desired
conductivity is entered into the controller through the front panel. As this limit is
exceeded, a bleed valve is opened via an onboard control relay. The system’s
water, with higher concentrations of TDS, is bled resulting in fresh make-up water
being added, reducing the concentration of TDS in the cooling system.
In addition to the bleed relay,
MicroVision
has three (3) other onboard control relays
assigned as follows:
Relay 1 - Bleed control
Relay 2 - Inhibitor timer (selectable)
Relay 3 - Biocide A
Relay 4 - Biocide B
2.
MICROVISION FEATURES
2.1
Toroidal Probe
MicroVision uses a toroidal probe for conductivity measurement. The
measurement is made by passing an AC current through a toroidal drive coil,
which induces a current in the electrolyte solution (see Fig.1). This induced
current in turn, induces a current in a second toroidal coil, called the pick-up
toroid. The amount of current induced in the pick-up toroid is proportional to
the solution conductivity.
