User guide

Watlow EZ-ZONE
®
PM PID Controller • 90 • Chapter 9 Features
Calibration of Analog Inputs: (cont.)
15. Validate calibration process by utilizing a calibrator to the analog input.
16. Enter calibration offset as recorded in step 2 if required to compensate for sensor error.
Setting Electrical Input Slope [ELi;S] to 1.000 and Electrical Input Offset [ELi;o] to 0.000, restores factory
calibration as shipped from factory.
Filter Time Constant
Filtering smoothes an input signal by applying a first-order filter time constant to the signal. Filtering the
displayed value makes it easier to monitor. Filtering the signal may improve the performance of PID control
in a noisy or very dynamic system.
Adjust the filter time interval with Filter Time [`FiL] (Setup Page, Analog Input Menu).
Example: With a filter value of 0.5 seconds, if the process input value instantly changes from 0 to 100 and re-
mained at 100, the display will indicate 100 after five time constants of the filter value or 2.5 seconds.
Sensor Selection
You need to configure the controller to match the input device, which is normally a thermocouple, RTD or
process transmitter.
Select the sensor type with Sensor Type [`Sen] (Setup Page, Analog Input Menu).
Set Point Low Limit and High Limit
The controller constrains the set point to a value between a set point low limit and a set point high limit.
Set the set point limits with Low Set Point [`L;SP] and High Set Point [`h;SP] (Setup Page, Loop Menu).
There are two sets of set point low and high limits: one for a closed-loop set point, another for an open-loop
set point.
Scale High and Scale Low
When an analog input is selected as process voltage or process current input, you must choose the value of volt-
age or current to be the low and high ends. For example, when using a 4 to 20 mA input, the scale low value
would be 4.00 mA and the scale high value would be 20.00 mA. Commonly used scale ranges are: 0 to 20 mA, 4
Unfiltered Input Signal
Time
Temperature
Filter Time Constant
Filtered Input Signal
Time
Temperature
Set Point Range (must be between Range High and Range Low)
Low Limit of selected functional range
High Limit of selected functional range
G
as Pressure
Ran
g
e Low and Ran
g
e Hi
g
h
Range High Range (between High Limit of Sensor and Range Low)
Range Low Range (between Low Limit of Sensor and Range High)
Set Point Low
Set Point High