Siemens SIWAREX WP251, Руководство пользователя

Страница: 30 / 220

Connection
6.2 24 V connection
SIWAREX WP251
30
Manual, 12/2015, A5E37203357A
6.2 24 V connection
The 24 V DC supply voltage is connected to the electronic weighing system via the
corresponding terminals.
Table 6- 1 Connection of the 24 V supply
Labeling Function
L + +24 V voltage supply
M Ground voltage supply
6.3 Connecting the load cells
Overview
Sensors equipped with strain gauges (DMS full bridge) can be connected to the SIWAREX
WP251 electronic weighing system. These sensors meet the following requirements.
● Characteristic value 1.... 4 mV/V
● The power supply for the load cells is 4.85 V.
● To check the maximum possible number of load cells that can be connected to a WP251,
the following condition must be met:
–
Scale operation without Ex interface: (input resistance of load cell) / (number of load
cells) > 40 Ohm
– Scale operation without Ex interface: (input resistance of load cell) / (number of load
cells) > 50 Ohm
Rules
Observe the following rules when connecting analog (strain gauge) load cells:
1.
The use of a junction box (SIWAREX JB junction box) is required when more than one
load cell is connected (the load cells must be connected in parallel). If the distance of a
load cell to the SIWAREX WP251 or the junction box is greater than the available length
of the load cell connection cable, use the SIWAREX EB extension box.
2. The cable shield is always applied at the cable gland of the junction box (SIWAREX JB)
or the extension box. If there is a risk of equipotential bonding through the cable shield,
connect a equipotential equalization conductor parallel to the load cell cable.