Watlow CAS200 - Manual (Page 66)

Chapter 4: Setup CAS200 User’s Guide
54 Watlow Anafaze
Linear Scaling Menus
The linear scaling menus appear under the Setup Channel
Inputs main menu. Linear scaling is available for linear
and pulse inputs only. It lets you scale the "raw" input
readings (readings in millivolts or hertz) to the engineering
units of the process variable.
NOTE! The linear scaling menus will only be present if
you set the channel’s input type to Linear (or, for
channel 17, to Pulse).
For linear inputs, the input reading is in percent (-16.6 to
100%) representing the -10 to 60mV input range of the
CAS200. For pulse inputs, the input reading is in hertz
(cycles per second.) The scaling function is defined by two
points on a conversion line, the high PV and the low PV.
High PV is the high end of the input in engineering units,
and the low PV is the low end. The engineering units of the
process variable can be any arbitrary units.
The example below shows a high PV of 20 psi and a low PV
of 0 psi. The high reading is the high end of the input signal
(where 60mV = 100%).
Before you enter the values that determine the two points
for the conversion line, you must choose an appropriate
display format. The CAS200 has six characters available
for process variable display; select the setting with the
desired number of decimal places before and after the
decimal point. Use a display format that matches the range
and resolution of the process variable. The display format
you choose is used for the setpoint, alarms, deadband, and
alarm deviation.
20 PSI
Hi PV
Lo PV
0 PSI
0% Lo
Rdg Hi
Rdg
0mV
100%
60mV
Process
Variable
Input Reading