Watlow Series 96 - Manual (Page 22)

5 . 3 ■ F e a t u r e s Wa t l o w S e r i e s 9 6
Input
Calibration Offset
Calibration offset allows a device to compensate for
an inaccurate sensor, lead resistance or other factors
that affect the input value. A positive offset increas-
es the input value, and a negative offset decreases
the input value.
The input 1 offset value can be viewed or changed
with Calibration Offset 1 [CAL1] (User Menu).
Figure 5.3a Calibration offset
Time
Temperature
Temperature Reading
from Sensor
Actual Process Temperature
Negative Calibration Offset will
compensate for the difference
between the Sensor Reading and
the Actual Temperature
Filter Time Constant
A time filter smooths an input signal by applying a
first-order filter time constant to the signal. Either
the displayed value or both the displayed and con-
trol values can be filtered. 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.
View or change the Input 1 time filter with Filter
Time Constant 1 [Ftr1] (Input 1 Menu). A positive
value affects only the viewed values. A negative
value affects both the viewed and control values.
Figure 5.3b Filtered and unfiltered input signals.
Unfiltered Input Signal
Time
Temperature
Filtered Input Signal
Time
Te
mperature
Sensor Selection
You need to configure a controller to match the input
device, which is normally a thermocouple, RTD or
process transmitter. When you select an input
device, the controller automatically sets the input
linearization to match the sensor. It also sets high
and low limits, which in turn limit the range-high
and range-low values. Use Sensor Type 1 [SEn1] and Input 1 [In1`]
(Input 1 Menu) to select the appropriate sensor for
Input 1.