17
PW20i
HBM
A1269-2.0 en/de/fr
6.2
Supply voltage
Regulated dc voltage of +12 ... +30 V is required to operate the measurement
electronics and serial communication.
Voltage source requirements:
•
The supply voltage must be sufficiently smoothed (rms value less residual
ripple > 12 V).
•
The PW20i electronics have a low loss regulator that consumes 1.5 W
during operation. The power consumption is therefore dependent on the
level of the supply voltage:
]
[
1.5
]
[
V
Voltage
W
A
Power Requ.
=
•
When switched on, the electronics briefly consume a current of approx.
0.15 A. To ensure a safe start-up, the power supply must be able to provide
this current without a limit being triggered. It is particularly important when
supplying several PW20i load cells from one power supply unit. In contrast,
the continuous loading is calculated from the equation shown above.
•
Connection to a wide-ranging supply network is not permitted as this often
causes interfering voltage peaks to be coupled into the transducer. Instead,
a local power supply must be provided for the PW20i load cells (even when
grouped).
•
The supply voltage must be insulated from the shield potential. A connection
from GND to the enclosure is not necessary, but the maximum potential
difference can only be 10 V. Should it be necessary, a separate cable can
be used to establish potential equalization between the PW20i and the
(PC/PLC) master (earthing concept). Cable shielding must not be used for
this potential equalization.
•
The power supply ground wire (GND) is also used as the reference potential
for the interface signals and the control input.
•
In layouts with several transducers, the power supply can be installed
together with the RS-485 bus lines in a 6 pin cable (e.g. with HBM junction
boxes). Ensure that there is sufficient wire cross-section provided as some
cable sections will conduct the supply current for all the connected PW20i
load cells.
