How to Build a Current Loop System with Compact FieldPoint? Hardware: Compact FieldPoint>>Analog I/O Modules
Problem: I want to build a 4 - 20 mA current loop system with Compact FieldPoint. Which module should I use and configurations are possible? Solution: When choosing which cFP module you should use for your current loop application, there are a few aspects that are important to note since not just any basic Analog Input module will suffice. Isolation Without properly circuit isolation, a ground loop can form. Ground loops may cause offset errors in your measurements. Also, large common mode voltages caused by ground potential differences can damage any data acquisition (DAQ) device. With Compact FieldPoint, daisy chaining a power supply between modules by connecting V terminals between terminal blocks will remove isolation. Shunt Resistor Most DAQ devices measure voltage. A highly effective and accurate method of measuring current is to place a precision shunt resistor between the leads of the DAQ amplifier to convert the current signal into a voltage measurement. The Compact FieldPoint modules that contain these two aspects and are suitable for current loop systems are: cFP-AIO-610
cFP-AIO-600 cFP-AI-111 cFP-AI-110 cFP-AI-100 There are two main configurations for Compact FieldPoint modules - one configuration with an external power supply and one without. With an external power supply, it can be hooked directly into the cFP current module as in Figure 1. If the transducer for your current loop system does not require an external power supply, then you can use the configuration in Figure 2.  Figure 1  Figure 2
Related Links: Developer Zone: 4 – 20mA Current Loop Tutorial Attachments:
Report Date: 02/21/2008 Last Updated: 04/23/2008 Document ID: 4IKG5NSG |
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