Advantech Data Acquisition Modules ADAM 4000 - Manual (Page 13)

Chapter 2
Chapter 2 installation Guideline 2-3
Power supply
For the ease of use in industrial environments, the ADAM modules
are designed to accept industry standard +24 V
DC
, unregulated power.
Operation is guaranteed when using any power supply between +10 and
+30 V
DC
. Power ripples must be limited to 5 V peak to peak while the
voltage in all cases must be maintained between +10 and +30 V
DC
. All
power supply specifications are referenced at module connector. When
modules are powered remotely, the effects of DC voltage drops must be
considered.
All modules use on-board switching regulators to sustain good
efficiency over the 10 to 30 V input range; therefore, we can assume
that the actual drawn current is inversely proportional to the DC voltage.
The following example shows how to calculate the required current that
a power supply should provide.
Assume that a +24 V
DC
is used for five ADAM-4011 Analog Input
Modules, and the distance between modules and power supply is not
significant enough to cause a DC voltage drop. One ADAM-4011
module consumes a maximum of 1.2 Watts (W). The total required
power will equal to 5 x 1.2=6 W. A power supply of +24 V
DC
should
therefore be able to supply a minimal current of 6 / 24=0.25 Amps.
Small systems may be powered by using wall-mounted modular
power supplies. Also, when modules operate in long communication
lines (>500 feet), it is often more reliable to obtain power locally
through modular power supplies. These inexpensive units can be easily
obtained from any electronic retail stores.
The power cables should be selected according to the length of the
power lines and the number of modules connected. When implementing
a network with long cables, the use of thicker wire is more suitable due
to the limitation of DC voltage drop. Furthermore, long wires can also
cause interference with communication wires.