Power Requirements; Analog Load Cell Connections - Mettler Toledo IND246 Guide D'installation

The integrity of the power ground for equipment is important for both safety
and dependable operation of the terminal and its associated scale base. A
poor ground can result in an unsafe condition should an electrical short
develop in the equipment. A good ground connection minimizes extraneous
electrical noise pulses. The IND246 should not share power lines with noise-
generating equipment. To confirm ground integrity, use a commercial branch
circuit analyzer. If adverse power conditions exist, a dedicated power circuit or
power line conditioner might be required.
FOR CONTINUED PROTECTION AGAINST SHOCK HAZARD CONNECT TO
PROPERLY GROUNDED OUTLET ONLY. DO NOT REMOVE THE GROUND PRONG.

Power Requirements

The terminal requires 85 to 264 VAC (at 167 mA maximum) with a line frequency
of 49 to 61 Hz of power and is internally fused at 1.0 amps, 250 volts.

Analog Load Cell Connections

TO AVOID DAMAGE TO THE PCB OR LOAD CELL, REMOVE POWER FROM THE IND246
TERMINAL AND WAIT AT LEAST 30 SECONDS BEFORE CONNECTING OR DISCONNECTING ANY
HARNESS.
Load cell connections are made to the load cell connector located on the main
board as shown in Figure 2-14.
The AC version of the IND246 terminal is designed to power up to eight 350-ohm
load cells (or a minimum resistance of approximately 43 ohms). The battery
version of the IND246 terminal is designed to power up to four 350-ohm load cells
(or a minimum resistance of approximately 87 ohms). To confirm that the load
cell load for this installation is within limits, the total scale resistance (TSR) must
be calculated. To calculate TSR:
TSR =
Ensure that the TSR of the load cell network to be connected to the IND246 has a
resistance greater than the minimums listed above before connecting the load
cells. If the resistance is below the minimum, the IND246 will not operate properly.
In addition, the maximum cable distance must be reviewed. Table 2-3 provides
recommended maximum cable lengths based on TSR and cable gauge.
Table 2-3: Recommended Maximum Cable Lengths
TSR (Ohms)
(meters/feet)
350
IND246 Terminal Installation Manual
WARNING
WARNING!
Load Cell Input Resistance (Ohms)
Number of Load Cells
24 Gauge 20 Gauge
(meters/feet)
243/800 610/2000
16 Gauge
(meters/feet)
1219/4000
2-11