14
17.
PV2 (Process Variable 2)
– Refers to analog input two. Normally this is used for the set point input signal.
18.
Relay
– In this manual, this refers to the alarm output contact. When an alarm condition is satisfi ed the
contact (relay) will close the N/O (Normally Open) relay and open the N/C (Normally Closed) relay.
19.
Residual
– Refers to either Free or Total Chlorine Residual reading. The units of measure are either mg/l
or PPM and it must be a positive number or zero. In terms of the HC-220, discussion is focused on the
4-20mA or 1-5V signal representing the Residual value.
20.
Residual/Other Control
– Refers to the Set Point control method. In this method, the user indicates
the desired Residual or Other set point and the HC-220 will automatically adjust chemical feed rate to
maintain that set point.
21.
Set Point
– In this manual, this refers to a desired value for the Residual or Other reading. It is the specifi c
Residual or Other reading that is chosen by the user and that the user would like the system to maintain.
22.
Threshold
– In this manual, this refers to the parameter selected in PV1 input setup (See Section III.1f.).
This is the value of PV1 that will be considered as zero PV1 input for control purposes. For PV1 between
minimum and threshold, the control calculations will consider PV1 to be zero. For control purposes, the
HC-220 will rescale the PV1 input (linearly from 0 – 100%) from PV1 Threshold to PV1 Full Scale.
The threshold value is expressed in the units used to display the PV1 input.
