Rockwell Automation 1788 NetLinx Media Checker Users Manual - Manual (Page 29)

Calculating Trunk, Drop, or Tap Lengths 29
1788-UM002A-US-P – April 2000
Calculating Trunk, Drop, or Tap Lengths
When you test a cable that has drops or taps, the
MediaChecker reports the length of the trunk, plus the
total length of all the drops or taps on the trunk.
This section shows how to calculate the length of just the
trunk or the total length of just the drops or taps.
DeviceNet and DH+/RIO Length Calculations
Formulas:
Measure drop lengths with the MediaChecker or a tape measure.
•
Trunk length = Measured length – Total actual length of drops
•
Total drop length = Measured length – Trunk length
Example 1: Calculating trunk length
A cable measures 270 ft long. The cable has 2 drops of 15 ft each.
Trunk length = 270 ft measured length – 30 ft drop length = 240 ft trunk length
Example 2: Calculating total drop length
A cable measures 788 ft long. The trunk is 400 ft long.
Total length of drops = 788 ft measured length – 400 ft trunk length = 388 ft total drop length