Watlow ez-zone pm - Ten Point Linearization; Outputs; Duplex; NO-ARC Relay

Watlow EZ-ZONE
®
PMI Controller • 190 • Chapter 9 Features
Ten Point Linearization
The linearization function allows a user to re-linearize a value read from an analog input.
There are 10 data points used to compensate for differences between the sensor value read
(input point) and the desired value (output
point). Multiple data points enable compensa-
tion for non-linear differences between the
sensor readings and target process values over
the thermal or process system operating
range. Sensor reading differences can be
caused by sensor placement, tolerances, an
inaccurate sensor or lead resistance.
The user species the unit of measurement
and then each data point by entering an input
point value and a corresponding output point
value. Each data point must be incrementally higher than the previous point. The lineariza-
tion function will interpolate data points linearly in between specied data points.
Note:
Output Point 1 will be the minimum value that can be displayed, and Output Point 10
will be the maximum value that can be displayed. Consider setting Output Point 1 to the
minimum operating range, and Output Point 10 to the maximum operating range; for that
sensor type.
Outputs
Duplex
Certain systems require that a single process output, control both heating and cooling out-
puts. An EZ-ZONE
®
PM controller with a process output can function as two separate outputs.
With a 4 to 20mA output the heating output will operate from 12 to 20mA (0 to +100 percent)
and the cooling output will operate from 12 to 4mA (0 to -100 percent).
In some cases this type of output is required by the device that the EZ-ZONE PM controls,
such as a three-way valve that opens one way with a 12 to 20mA signal and opens the other
way with a 4 to 12mA signal. This feature reduces the overall system cost by using a single
output to act as two outputs.
Outputs 1 and 3 can be ordered as process outputs. Select duplex dUpL as the Output Func-
tion fn (Setup Page, Output Menu). Set the output to volts voLt or milliamps ЛЏa with Type
o.ty. Set the range of the process output with Scale Low S.Lo and Scale High s.hi.
NO-ARC Relay
A NO-ARC relay provides a signicant improvement in the life of the output relay over con-
ventional relays. Conventional mechanical relays have an expected life of 100,000 cycles at
the rated full-load current. The shorter life for conventional relays is due to the fact that
when contacts open while current is owing metal degradation occurs. This action produces
unavoidable electrical arcing causing metal to transfer from one contact to the other. The
arcing conditions continue on each subsequent contact opening until over time the resistance
through the contacts increases causing the contacts to increase in temperature. Eventually,
the contacts will weld together and the relay remains in the on state.
2
3
4
5
6
7
8
9
Reading from Sensor
without Linearization
(Actual Value)
Input Point 1
Output Point 1
Input Point 10
Output Point 10
Offset Zone
Reading from Sensor
with Linearization
(Displayed Value)
No Offset
Temperature
Time