PT610, PT620, PT630
Instruction Manual
13
4.4 CONNECTING THE LOAD CELL
Warning:
After load cell connection to the instrument, welding on the mechanical structure or fittings is
not recommended. Disconnect all connectors from the indicator before any welding on the mechanical
hardware.
The load cell wiring should be installed carefully before energising to avoid damage to the instrument
and load cells. The combined input resistance of the load cells that you want to connect should be more
than 42Ω. Do not bind the load cell cables together with other cables as it could result in cross-talk
interference. Please also keep them well away from the AC power cables. Load cell connection details
are shown below. In 4-wire installations the sense and excitation pins with the same polarity should be
connected together in the connector (connect Sense+ to Exc, Sense- to Excitation-).
4 wire LC connection
6 wire LC connection
If you have a junction box in your system, use 6 wire cable between the instrument and the junction
box, and for 4 wire load cells connect Sense and Excitation in the junction box instead of at the indicator
for better performance.
Warning:
Always connect Sense pins to Excitation pins for 4 wire connection. Non-connected sense
pins may cause the wrong Excitation voltage measurement and create an accuracy problem.
Warning:
Normally connect the load cell cable shield to the reference ground or shield pin of the load
cell connector. In some load cells the cable shield is connected in the load cell body and grounding the
shield at both ends can cause instabilities.
4.5 POWER SUPPLY AND GROUNDING
The weighing instrument measures very low signal levels. The quality of the power supply and
grounding will affect the accuracy and the safety of your measuring system. It is very important that the
instrument should not share power lines with noise-generating parts such as heavy load switching
relays, motor control equipment, inductive loads, etc. If the condition of the mains power supply in the
plant is poor, install a special mains power line and grounding. Be sure, the power supply is switched of
before connection.
Warning
:
Before modifying the instrument, turn the power off and wait at least for 30 seconds.
Warning:
Connect the power supply grounding
pin to the reference ground.