Watlow Controls 8LS, User Manual

Page: 65 / 140

Setup
8LS User’s Guide 57
Low RDG Display
Selectable range: 0-9999.
The low input reading is referenced to 60mV and is calculated using this
equation:
Linear Input Scaling Example:
Problem :
You want to connect a pressure sensor to be able to read pressure
directly in PSI. The sensor has an output of 4-20mA over a range of
100-400PSI. The 4-20mA is converted to 12-60mV. How will you set
the input scaling?
Solution:
1. Set the High PV to 400 and enter the units as P, S, and I.
2. Calculate the High RDG and enter it:
3. Set the Low PV to 100 and enter the units as P, S, and I.
4. Calculate the Low RDG and enter it:
1 2 3 4 5 6 7 8
LOOP PROCESS UNITS
ALARM
SETPOINT
STATUS OUTPUT%
1 LO RDG
? 0
LOW RDG = (1000)
(Sensor output @ Low PV)
60 mV
*
High RDG = 1000
(60 mV)
(60 mV)
*
Sensor output @ high PV
Full scale 8LS input
=1000
Low RDG = 1000
(12 mV)
(60 mV)
*
Sensor output @ low PV
Full scale 8LS input
=200