Hi

We have just taken delivery of a DT80M to use for collecting data when brake testing. To give us the vehicle speed we have obtained a CAN bus interface which gives us a pulse on a 12V signal that equates to 1Hz = 1 mph. I am stuggling to understand how I can read this signal to calculate the vehicle speed. Has anyone got any suggestions? I have tried the analogue frequency method and the high speed counter in the dex configuration section but without success. Is a manual channel a possible solution?

Regards
Andrew

Hi Andrew

I've done this with a 5th wheel. A 5th wheel will give the most accurate result as you don't have to worry about rolling diameters etc.

The other way I have done is to put a hall effect transducer on the ABS gear to count the teeth.

Check the CAN outputs true speed rather than indicated speed. The speed displayed is true speed plus 5 kmh.
What type of output is on the CAN unit? E.g. contact closure, open collector, other.
Also what a Voltage levels is it?

Cheers

Roger

Hi Roger

Thank you for your reply, however I have managed to get a reading by adjusting the sample rate on the analogue channel. The CAN bus sends a 12V (nominal) pulse so using the analogue frequency channel we can now get a speed reading. However we now have another problem in that the dex interface is not loading when we plug the usb cable into the PC.

Regards
Andrew

Update on the dEX issue, the interface finally loaded, but it took about five minutes!