Watlow CLS - Manual (Page 47)

Installation
CLS User’s Guide 39
Scaling and Calibration
The CLS provides offset calibration for thermocouple, RTD, and other
fixed ranges, and offset and span (gain) calibration for linear and pulse
inputs. (Offset and span calibration convert linear analog inputs into
engineering units using the Mx+B function.)
In order to scale linear input signals, you must:
1. Install appropriate scaling resistors. (Contact Watlow Anafaze's
Customer Service Department for more information about install-
ing scaling resistors.)
2. Select the display format. The smallest possible range is
-.9999 to +3.0000; the largest possible range is -9999 to 30000.
3. Enter the appropriate scaling values for your process.
For more information about input scaling and input offset, see Setup
Loop Inputs in Chapter 4: Setup.
T/C Inputs
WARNING
The CLS uses a floating ground system. Therefore:
Isolate input devices or host computers connected through
communications cables (like RS-232) from earth ground.
Use ungrounded thermocouples with the thermocouple
sheath electrically connected to earth ground.
Use optically isolated RS-232 devices to isolate earth
grounded host computers from the CLS.
When you use grounded T/Cs, tie the thermocouple shields
to a common earth ground in one place. Otherwise any
common mode voltages that exceed 5 volts may cause
incorrect readings or damage to the controller.
WARNING
The 16CLS has single ended inputs, offering little protec-
tion from common mode voltage sources. Therefore
Watlow Anafaze highly recommend that you use
ungrounded thermocouples with the external thermocou-
ple sheath electrically connected to earth ground.