Watlow MLS-PM, User Manual

Page: 52 / 144

Installation
MLS User’s Guide 39
2. Select the # of digits and decimal point location for the full scale PV
display. The smallest possible range is -0.9999 to +3.0000; the largest
possible range is -9999 to 30000.
3. Enter the zero and full scale values (process variables) you want dis-
played when the input signal is at zero and full scale.
T/C Inputs
WARNING
Use ungrounded thermocouples (thermocouples
which have the T/C junction isolated from the
metal protection sheath). Grounded thermocou-
ples will damage the MLS if voltage between the
loops exceeds 10 volts.
If you are installing the MLS in an existing tem-
perature control system, check all grounded T/C
assemblies in the system. Make sure there is no
voltage between T/C leads.
You can connect all T/C types directly to the MLS. Watlow-Anafaze
provides J, K, T, R, S, and B type linearization and cold junction
compensation. (Other thermocouple types require custom input ranges;
contact Watlow-Anafaze for more information about them.)
Wiring Recommendations
Follow these recommendations for thermocouple wiring:
• Use 18 or 20 AWG thermocouple (T/C) extension wire for all ther-
mocouple inputs.
• Most T/C wire is solid unshielded wire. Use shielded wire if required
at your installation; ground one end only.
• Use less than 500' of T/C extension wire. Longer wire runs exceed
accuracy and source impedance specifications.
• Install T/C wiring in a separate conduit away from AC power (the
120 Vac supply) and high power (240 Vac or higher) wiring.