Watlow CPC400 - Manual (Page 73)

CPC400 Series User’s Guide Chapter 3: Operation and Setup
Doc. 0600-2900-2000 Watlow Anafaze 59
Figure 3.6 Input Scaling
The range for set points and alarms is bound by the process
variables that correspond to the 0 percent and 100 percent
input signals (or the 0 Hz and 2000 Hz signals for pulse in-
puts). Bear in mind that the range for set points and
alarms is not bound by the low and high process variable
ranges 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 -999.9 to
3000.0, because the sensor measures PSI in tenths.
• For the Input signal low and Input signal high param-
eters, 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 sensor 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