EEVblog Electronics Community Forum
Electronics => Projects, Designs, and Technical Stuff => Topic started by: yoda_bear on May 12, 2017, 04:47:58 pm
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So I purchased a Siglent 2042X function generator to simulate a vehicle speed sensor being connected to an ECM. I noticed my function generator didn't come with any probes, I should have known better. That said, where can I purchase some probes or is it easier to build your own?
Just looking for advice from someone who has been in my position.
Thanks.
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Function generators are not normally used with probes. I have a cable with a couple of grabber clips on the end that I use with mine, and I occasionally make up a custom cable.
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Sorry bad choice of words there.
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There are 3 main types of signal types that are likely to be fed to an ecu, first is hall effect, this is an open collector npn transistor with a limited collector current, generally 5mA max load. This type assumes pullup for npn or pulldown for pnp. Generally 10-22k, this type can be approximated to a signal gen biased above 0v with a diode pointing towards the generator.
Next up is totem pole, this is still transistors. 0.3/0.7v to 1v less than sender.supply, generally 500uA loading, this is essentially the same as the first without the diode.
And finally is inductive, this is a high impedance current mode differential signal, and its amplitude begins very small for small signals 50-70mV for 1kmph, getting up to 400mv around 10kmph, and peaking at around 2.8v at 120kmph, if you just want to feed in an input then set it for about 2.5v or 5v pk-pk, 0v centered.
There are some others like coil and points but i doubt that would be fed to an ecu.
If in doubt begin with inductive.