Voltage Table - Metasys - LIT-12012443 - Software Application - MS-FIT100-0 Field Inspection Tool

MS-FIT100-0 Field Inspection Tool User Guide

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MS-FIT100-0 Field Inspection Tool
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User Guide
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Table 1. Voltage Table
Voltage Communication State Meaning Acceptable Range 1
Bias Voltage Either Idle or Active Communication The + to COM Reading, - to COM or + to -. Typically used such as + is biased to com, -, etc. It is the voltage applied to the bus by the EOL termination on the controller to establish a properly biased bus. See notes below for acceptable ranges based on active or idle communication states.
Idle Voltage Idle The term idle voltage could be referring to + to COM, - to COM or the + to – (differential) Reading. What it really means is no communication is occurring at the time of the reading. Typically near 2.7 (+ to com) -2.3 VDC (- to com) with a differential (+ to -) of 0.4VDC. Can vary with wire length & bus load but should not be lower than ~0.2VDC differential or higher than ~0.9VDC differential.
Idle Differential Voltage Idle This is typically referring to the + to – voltage reading without communication. ~0.2 to ~0.9 VDC
Communication Voltage Active The term communication voltage could be referring to + to COM, - to COM or the + to – Reading. Communication is occurring at the time of the reading. See Bit Voltage and Differential Voltage below.
Bit Voltage Active + or – with respect to COM when communication is occurring. +2.0 to +4.0 VDC (+ to Com), -2.0 to -4.0 VDC (- to Com). When comparing the absolute value of these two readings, there should be no more than approximately a 0.2 VDC difference.
Differential Voltage, Total Voltage Active The + to COM Reading plus the absolute value of the - to COM Reading when communication is occurring. 2.5VDC to 8VDC is acceptable.
1 These voltages should typically not be read with a Volt-Ohm-Meter (VOM). Use the FIT instead. Idle bus voltages are read with a VOM when communication is not occurring. When FIT is connected to a bus and then powered on, it will display Offline if the bus is Idle.