72-900-06 Rev. F
Page 12 of 38
3.8 Flow Switch Input
It is recommended that a flow switch or auxiliary dry contact be used to make outputs
inoperative when the cooling tower is shut down. Connect detection wires to P1 to use
this interlock feature. This is active – closed: open = no flow; closed = flow.
If the controller does not have a flow switch, a jumper wire must be
connected across P1.
3.9 Sensor (probe) Connection Input
The controller is supplied with sensors prewired. Depending on the model, the
conductivity probe wires are connected to Probe 1, pH sensor on Probe 2, ORP sensor on
Probe 3, and Make up conductivity on Probe 4.
Always depressurize the unit prior to removing a sensor.
3.10 Water Meter Input
Connect the water meter to P5 on the top board. Some models have additional water
meters on P6 through P10. In order to wire a dry contact type water meter or contact
closure to a 3-port digital input, connect the two leads to the signal and ground ports.
3.11 Drum Level Input
The drum level connections are labeled as, P2 for Level 1, P3 for Level 2, and P4 for level
3. These are active closed: closed = low level; open = level is OK. The input can also be
reversed (NO or NC) in the programming.
3.12 4-20mA Output
The 4-20mA outputs, ordered separately, can be used to remotely measure any of the
controllers probe inputs and any of the 4-20mA inputs. Connect the 4-20mA receiving
equipment to the 4-20mA boards pins are marked + (positive) and – (negative). The
polarity must be observed for proper operation. The 4-20mA output current range is
approximately 0 mA to 24mA. Resistive load range should typically be 300 Ohms with a
max rating of 1200 Ohm.
3.13 4-20mA Input
Model dependent, MicroVision EX can support up to two 4-20mA analog inputs. The 4-
20mA inputs, ordered separately, can be used to receive and data log signals from
sensors that transmit a 4-20mA output. Connect the 4-20mA equipment to the 4-20mA
boards pins are marked + (positive) and – (negative). The polarity must be observed for
proper operation.
Each 4-20mA analog input supports 2 wire loop or transmitter powered configurations.
Input resistance load is approximately 265 Ohms. Input voltage range is commonly 12V
or 24V. Up to 60V is permissible.
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