Network Communication Voltage Levels - Metasys - LIT-12012443 - Software Application - MS-FIT100-0 Field Inspection Tool

MS-FIT100-0 Field Inspection Tool User Guide

Product name
MS-FIT100-0 Field Inspection Tool
Document type
User Guide
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When the FIT is connected to a network of controllers it will measure the communication voltage levels of each individual controller. When looking at communication voltage levels on a network, it is important to note that the voltage levels are affected by many factors, such as wire length, wire gauge, number of controllers, network topology, EOL terminations, and the FIT connection on the bus. The FIT’s connection location affects the voltage readings taken. The controllers closer to the FIT typically have higher voltage readings than the controllers farther away from the FIT. It is therefore important to take note of the network location where the FIT is connected since the voltage readings are affected.

Differential voltage levels in the range of (2.5V to 8V) are expected on most properly functioning buses. The + line voltage and – voltage should be approximately equal or within 0.2VDC of each other on a properly wired and terminated bus.

Since the FIT is reading and calculating these voltages, they are only accurate for the bus segment to which the FIT is connected. If using communication voltages to troubleshoot, each bus segment should be read independently. Voltage readings where there are large voltage differences between the + line and – line can indicate a wiring problem such as a shorted, pinched, or open wire connection.