Voltage Menu; Idle Bus Menu; Bit Voltage Menu - Johnson Controls MS-FIT100-0 User Manual

amount of information is being transmitted and received. For Johnson Controls manufactured
equipment, Model and Vendor data are displayed.
For a complete list of all attributes, and modes see the Table 9. See
Levels for more information on bus voltage levels.

Voltage Menu

The voltage menu has three voltage reading modes available:
• Idle Bus Voltage
• Bit Voltage
• Meter

Idle Bus Menu

When selected, the Idle Bus Menu reads the bus bias voltage when no communications are
present. Proper idle bus voltage levels will not be displayed unless EOL termination is present. The
idle bus voltage menu shows the + line voltage with respect to the COM line and the – line voltage
with respect to the COM line. The FIT can still read this voltage on an active communication bus by
taking readings during communication pauses. For acceptable Idle Bus Voltage ranges, see
Levels and the Voltage
Note: It is possible and normal for there to be minor voltage fluctuations while reading Idle
Bus Voltages.
Idle Bus Voltage Levels
See

Bit Voltage Menu

The Bit Voltage menu displays in real time the voltage when communication is occurring on
the bus. The differential voltage and bit voltage (+, – line with respect to COM) from a controller
are shown on the display. Approximately every half second, a new voltage sample is taken
from the bus and displayed. The voltage sample could be from any controller on the bus that is
communicating at the time of the sample. Use the Bit Voltage mode for a quick look at the quality
16
Table.
Figure 10: Idle Bus Menu
for more information.
Network Communication Voltage
MS-FIT100-0 Field Inspection Tool User Guide
Voltage