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In this example the Ultra Twin is being used to control a rake on a screen,
which is filtering out solids in the inlet flow to a wastewater treatment plant.
This will be achieved by setting up a level application on both Point 1 and 2
and assigning the relays to the relevant point(s) to obtain the desired
control.
A high alarm has been assigned to Point 1 (Transducer 1), on the
upstream side and a low alarm, to Pointt 2 (Transducer 2) on the
downstream side. The Diff. Control, to operate the rake is on Relay 1, high
alarm, on Transducer 1 (upstream), is on Relay 2 and, low alarm, on
Transducer 2 (downstream) is on Relay 3.
This will operate as follows, when the level rises on the upstream side
and/or the level on the downstream side falls, resulting in a differential of
0.5 feet, (anywhere within the working span), indicating that the screen is
blocked, Relay 1 will come on and operate the rake. Once the level on the
inflow has decreased and the differential level falls to 0.1 feet Relay 1 will
switch off the rake.
Should the level on the upstream side rise, for any reason, to a level of 8.5
feet, Relay 2 will operate to give a high alarm, once the level has fallen back
to 8.0 feet the alarm will go off. A falling level in the downstream side, for
any reason, will operate Relay 3 at 1.0 feet giving an alarm for low level,
once the level has risen again to a value of 1.5 feet Relay 3 will reset.
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