Calculating Power Requirements for the FP-3000

Insufficient power is one of the main causes for problems observed with the FP-3000. This document explains how to calculate the power requirements for your bank, and how to provide power accordingly.

Bank Power Requirements

As with any FieldPoint bank, the power requirements depend on the network module, the I/O modules, and any devices being powered by the analog or digital outputs.

The power supply connected to the network module provides power to operate the entire bank of I/O modules via the backplane in the terminal bases. It does NOT provide power for the output signals (such as analog outputs) unless you add a separate power supply for the output module.

I/O Power Requirements

For an output module, the Vsupply and Common terminals of the terminal base must be wired and powered. Unless you add wires, these terminals are not electrically connected to the Vsupply and Common terminals of the network module. They are used for power and referencing of the I/O SIGNALS only (not the I/O module itself). For example, they are used with analog output, digital output, pulse width modulator, or counter modules to provide power for the outputs.

Note: The Vsupply and Common terminals of input modules do not need to be wired. However, if the inputs need to have a common ground, you should wire the Common terminal to the common of the incoming signals.

There are three ways to wire power for the outputs:

1. Power each module's outputs with a separate power supply. Do not cascade any of the Vsupply and Common terminals. This option provides the most isolation.
2. Power all the outputs by connecting a second power supply to the cascaded terminal bases (but not the network module). This establishes two independent grounds -- one for the backplane and one for the output modules. This allows for medium isolation without needing a dedicated supply for each output module.
3. Get power from the same supply as the FieldPoint modules by cascading the Vsupply and Common from the network module to the first terminal base, and then from terminal base to terminal base down the bank. This allows outputs to be powered by the same supply (assuming the supply can provide enough power to meet the demands of the modules AND the analog output currents). The major drawback is that a single ground is established for both the backplane and the input/output circuitry, defeating the isolation of the modules.

See the FP-3000 documentation for more information on powering and isolation.

See Also:
FieldPoint FP-3000 Network Module User Manual

Isolation

The Isolation rating is the maximum voltage differential that can occur between the common terminal on the terminal base (the input circuit's ground level) and the ground in the backplane of the module (the network module's ground level) without causing damage to the circuitry.

Safety Isolation (or working voltage) is the maximum voltage differential (per safety isolation specifications) that can be sustained between the common terminal on the terminal base (the input circuit's ground level) and the ground in the backplane of the module (the network module's ground level) while still allowing accurate measurements and safe working conditions for human operators.

Power Calculation

The standard calculation for FieldPoint power consumption is:

Power consumption = Network module's power draw + 1.15 * sum of I/O modules' power draw + Power draws of the outputs

The power requirement for the FP-3000 network module alone (no connected I/O modules) is 6 Watts. The power requirement of each I/O module is listed in the catalog and in the Operating Instructions pamphlet for that module. Add the I/O modules' requirements and multiply by 1.15 (to account for the power requirements of the terminal bases). If you are using a separate power supply for outputs, the third term in the calculation for the primary power supply's requirements will be zero.

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