Class-8 Heavy Truck Duty Cycle Project Final Report - Center for ...

Potential J1708 Issues
The J1708 data bus has a nominal 45 messages/second rate (9600
baud, 10 bits/character for J1708 networks, standard message length
of 21 characters). Querying 10 parameters at 5 Hz is equivalent to
50 messages/second—this does not count the message responses,
AirWeigh messages, or the normal functions of the J1708. As this will
exceed the capacity of the J1708 network, it is recommended that the
following steps be taken in the event a J1708 vehicle databus will be
used.
1) Set the sample rate for the eDAQ at 5 Hz for uniformity
2) Set the query rate to a lower value, such as 1 Hz. (Make note
of this value, as this will essentially be the “data refresh” rate.)
3) Set the invalid data timeout to a value substantially lower than
the sampling rate (for example, 5 seconds). Otherwise, invalid data
values will be recorded between samples.
9.3.5. Weather Station Notes
- The weather station should be set up to update every 1 s because it
is the smallest available interval.
- Set averaging interval to 1 s (smallest available interval), because
“average” values (rather than max, min, or peak) will be recorded.
D-93