Chemtrac HydroAct HA4, User Manual

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40 Chapter 3. Sensors
UV254 sensor side view
1. Sample inlet
2. Sample drain
The customer must install a valve to shut off the flow to the sensor when servicing is required
and a flow control valve to regulate the flow to 0.3-1.0 l/min. The recommended flow rate for the
sensor is approximately 0.75 l/min. This flow rate is regulated by the use of suitable flow control
valve on the inlet tubing. The test water must be allowed to flow unrestricted to the drain, and water
pressure at the sensor should never exceed 5 PSI (350 millibar). The UV254 sensor will operate
without recalibration or cleaning for an extended period of time under most water conditions. However,
if water has very high turbidity or large suspended particles, then at least a 5 micron sediment filter
is recommended to ensure accurate readings. The sensor should be attached to the wall at all four
provided mounting holes. The type of screws used will depend on the installation site. When selecting
the type of screws to be used, ensure that they will support the weight of the instrument. Both 24VDC
power and communication lines feed into the sensor via one fitting on the bottom of the sensor and
must be connected to the terminal block at the bottom of the enclosure.
3.1.2.3 Wiring
Connections for AC power and between the HydroAct 4 and UV254 sensor are indicated in the following
image.
Note regarding sensor card slot position:
If the analyzer is only equipped to work with a single sensor (as evident by there only being one
plugin card installed in slots 1 and slots 2 to 4 being empty) then the RS-485 sensor input card for the
UV254 sensor will be in the “Slot #1” position as shown in this diagram. Otherwise, if additional plugin