
4-20mA Option For Hallett 30
Released on 19/Aug/16 - X800099E Page 7 UV Pure Technologies Inc. © 2016
Warning and Alarm set points
There are two set points for a UV intensity fault on the Hallett unit. The signal
must remain below the set point for at least 3-5 seconds before an alert is
issued.
A UV Intensity warning is indicated by the green LED on, the valve (if supplied)
remains open, the Hallett unit issues an audible alarm and flashes the red LED
beside lamp graphic. A UV Intensity warning will occur when UV intensity signal
drops below first set point –see Chart 2 for corresponding values for Drinking
Water and Waste Water applications.
A UV Intensity alarm is indicated by the green LED not on, the valve (if supplied)
closes, the Hallett unit issues an audible alarm and turns on solid the red LED
beside lamp graphic. A UV Intensity alarm will occur when UV intensity signal
drops below the second setpoint –see Chart 2 for corresponding values for
Drinking Water and Waste Water applications.
Alarm Setpoint 0.5 63% 14 0.24 60% 14
Warning Setpoint 0.55 69% 15 0.28 70% 15
Chart 2
Net UV Transmittance
The input signal range of the Water UV sensor is 0-2.5 Vdc. This value
represents the UV Transmittance (UVT) of the water, the transmission of UV
through the quartz sleeve and the combined UV output from the right hand UV
lamp and reflector. With everything else constant, the net signal represents the
UVT of the water, thus the Net UVT. Accurate measurements of the Net UVT of
the water are based on a clean quartz sleeve. If the quartz cleanliness is not
100%, then the value displayed and transmitted will be somewhat lower that the
actual UVT.
For a typical Hallett system, the range of the Water UV sensor will be from 0.9
to 1.5 Vdc for a Drinking Water application, and from 0.4 to 1.1 Vdc for a Waste
Water application. This voltage value will be displayed on the top left hand side
of the 4-20mA unit. The transmitted value represents the Net UVT and it is a
calculated value based on both the maximum Water UV sensor value and the
Lamp UV sensor value –this method accounts for lamp aging (see note below
about the cleaning system and maximum Water UV sensor value). The NET
UVT is normalized from 0-100% and it is displayed on the top right hand side of
the 4-20mA unit - see Chart 3.