There are tachometer signals available on the vehicle CAN-bus. Can I use these signals instead of connecting my own tachometer signal?

A simple question should have a simple answer and that answer is “No”.

As usual, however, life is never that simple.

With modern ECU’s and vehicle buses, like the CAN-bus, there are many signals available like engine RPM or drive shaft RPM, for example.

But if taking a signal from an ECU output or from a CAN-bus output then the signal is not being taken directly from a sensor. It comes from a computer that has processed the sensor signal and that processing will have introduced a delay into that signal.

If any sort of signal processing is to be carried out on a signal then the signal should be taken directly from the sensor. If it is not possible to obtain access to the analogue voltage from the sensor already fitted and used by an ECU or CAN-bus then an external sensor should be fitted.

In short, an engineer would be expected to connect an external sensor or use a sensor already on the vehicle directly.

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James Wren

Application Engineer & Sales Manager at Prosig
James Wren is an Application Engineer and the Sales Manager for Prosig Limited. James graduated from Portsmouth University in 2001, with a Masters degree in Electronic Engineering. He is a Chartered Engineer and a registered Eur Ing. He has been involved with motorsport from a very early age with special interest in data acquisition. James is a founder member of the Dalmeny Racing team.

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