m
2000D
technical manual
Page 10
L
OAD
C
ELL CONNECTION
The main characteristic of a digital system is to prevent long analog load cell cable
connections between the load cell and the indicator. The installation strategy for a digital
system is to have the DLC junction box mounted as close as possible to the weighing
platform, to keep load cell cable runs between load cells and the DLC junction box as short
as possible, to eliminate contamination of load cell analog signals by RFI and EMI
interference.
Because the DLC junction box will be in close approximation to the load cells, losses in
load cell cabling will be kept to a minimum, and so the need for SENSE lines is
eliminated. For this reason, the DLC junction box do not include sense line terminals for
load cells. The load cell interface only requires EXCITATION and SIGNAL lines for a
total of 4 wires. Connecting a 6 conductor load cell cable to a DLC terminal recommends
the +SENSE and +EXCITATION conductors to be joined together and the –SENSE and –
EXCITATION conductors to be joined together respectively.
S
ERIAL
P
ORT CONNECTIONS
Serial ports can be configured in the normal RS232 modes and to RS485 or RS422 multi
drop modes. Before connecting to the serial port, consideration should be given to the
communications protocol and to any remote requirements to prevent damaging serial ports.
The recommended cable to be used with serial communication is 20 to 28 AWG with a
braided or foil shield. The maximum recommended cable length is 15 meters or 50 feet.
However much longer connections are possible if using a properly shielded, low-
capacitance cable. The shield on a serial cable should only be connected to the M2000D
indicators shield terminal for the serial port in question. Do not connect the shield on both
ends of the cable – one end should be floating (not connected).
DLC
C
OMMUNICATIONS
C
ABLE CONNECTIONS
The DLC communications cable is the heart of the M2000D system. This cable conveys
high-speed digital packetized data between DLC slaves and the M2000D indicator. This
data is error corrected and although some packets might be rejected, the overall system
provides a zero loss data path over a maximum of a 1000 feet of cable. The DLC digital
cable provides optical isolation between the indicator and each of the remote DLC slaves.
The cable should have 4 conductors, one pair for power delivery and one pair for data
communications. The cable should provide a separate foil shield for each pair plus a drain
wire to be connected to the M2000D shield terminal. Do not connect the shield on the
other end of the cable to anything. The recommended cable to be used is type 22 AWG
(0.32 sq. mm), with each pair of conductors foil shielded.
