Hi All
Wonder if someone has come across this before or am I just being daft.
Trying to get a scope pattern from a 05 Focus ABS sensor, according to autodata it is a magneto resistive type which produces milliamps when the wheel is rotated.
I have checked the voltage supply going to the sensor, this corresponds to the data as supplied by autodata.
When using the pico for a digital sensor I cant see how to set it up read milli amps again as per autodata.
I should be able to see a nice square wave form according to autodata.
Any ideas people.
To see the current on those you need a K110 micro amp probe. They are stupidly expensive but the only one I know of that will do it. Also useful for AFR sensors and other things.
We used to stock them and then Amazon undercut us on the price so we quit carrying them.
I have not tried on a Ford Focus but there are 2 other methods if you do not have a K110 probe.
1. On many of these magnetoresistive sensors you can see the switching waveform by measuring between 0V (chasiis ground) and one side of the sensor. You will see what looks live a DC voltage (different values on different vehicles) but if you zoom in on the signal you will see a square wave of a few mV when you spin the wheel. Try this on a known working sensor first.
2. The signal usually switches from 5mA to 15mA which is a bit small for the 20A/60A probe (although with the resolution enhance to 16 bits its just about visible). If however you can pass / wrap a wire carrying the signal through the jaws of the current clamp 10 times then the current clamp sees 50mA switching to 150mA which is more than enough. I have done this using the 6 way break out leads before, but the best method depends on where the connector is.
Just finished diagnosing a bad abs sensor on a 2005 torrent, on these new sensor types the signal can be on the supply line which is battery voltage or on the return line to resistor in the ABS computer. If you switch to AC voltage on the line you are seeing the small pattern it isolates the square wave and you can see it clearly.