Watlow Series D8 - Manual (Page 107)

Series D8 User’s Guide Chapter 4: Operation and Setup
Doc. 0600-3120-2000 Watlow Anafaze 89
Figure 4.6 Input Scaling
The range for set points and alarms is bound by the process
variables that correspond to the 0 percent and 100 percent in-
put signals. Bear in mind that the range for set points and
alarms is not bound by the low and high process variable rang-
es that you enter in the scaling parameters.
Input Scaling Example: 4 to 20 mA Sensor
Situation
Suppose the controller has a 0 to 20 mA process input that is
connected to a pressure sensor. The pressure sensor has a
range of 4 to 20 mA, representing 0.0 to 50.0 pounds per
square inch (PSI).
Setup
Set the scaling parameters in the Input menu as follows:
•
For the Input type parameter, choose process.
• For the Disp format parameter, choose -999.9to 3000.0,
because the sensor measures PSI in tenths.
• For the Input signal low and Input signal high parame-
ters, use the minimum and maximum range of the sensor.
In this case, the sensor range is 4 to 20 mA. The range
must be expressed in percent of full scale. To determine
the percentages, divide the minimum and maximum sen-
sor range (4 mA and 20 mA) by the maximum signal that
the controller can accept (20 mA):
•
Input signal low
= 4 mA/20 mA = 0.2 = 20%
0% 100% 20%
Input Signal
Pr
ocess V
ariab
le
8
28
Rang
e f
or set points and alarms