55505 geartooth sensor bench test - bad sensor or bad me?

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55505 geartooth sensor bench test - bad sensor or bad me?

Postby Mr Bombjoy » Sun Jun 11, 2017 11:25 am

I have a brand new 55505 hall/geartooth sensor and I rigged up a 9v portable tester. The idea was to see if the 55505 could accurately pick up the teeth on an OEM distributor reluctor wheel, or if I would need to build up a 50/50 type wheel instead.

Connected it per the datasheet:
9V to VDD
GND to GND
VOM + to output, - to GND

Ouput is always high (well, high minus some voltage drop). Seems like no matter how I arrange my VOM I can't see more than a few mV of change in the presence of ferrous metal (positive switching, negative switching). Tried various pull up and pull down arrangements on the output no resulting change.

Brought it inside to the electronics bench and hooked it up to regulated 5v but got the same result. Measured outputs on my Rigol scope - If I zoom way way way in I can see the tooth transitions but there is no way it would be suitable in an automotive environment. DS says it should be VDD minus some standard semiconductor tax (2V-ish or so). I see maybe a 0.02v drop in the presence of metal. Drop in the presence of metal seems backwards, too.

I'm thinking it's a bad sensor right out of the gate. Has anyone else tried something similar?
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Re: 55505 geartooth sensor bench test - bad sensor or bad me

Postby billr » Sun Jun 11, 2017 4:59 pm

Give me a hint: who makes that "55505" sensor? Or, post a link to the DS.
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Re: 55505 geartooth sensor bench test - bad sensor or bad me

Postby dontz125 » Mon Jun 12, 2017 5:37 am

It's a Littelfuse item. The DS calls for Vcc-2v for 'High', and ~ 0.6v for 'Low', with an internal pull-up.

If you aren't a) holding the test piece too far away, or b) using non-magnetic stainless / aluminum / etc, then it sounds like a bad part.
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Re: 55505 geartooth sensor bench test - bad sensor or bad me

Postby billr » Mon Jun 12, 2017 8:55 pm

Are you spinning a toothed wheel in front of it, while bench testing? That sensor doesn't specify that it is a "zero speed" sensor, just waving a target in front of it might not work.
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Re: 55505 geartooth sensor bench test - bad sensor or bad me

Postby dontz125 » Mon Jun 12, 2017 8:59 pm

I'm away from my desktop; does the datasheet specify a minimum speed or frequency?
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Re: 55505 geartooth sensor bench test - bad sensor or bad me

Postby Mr Bombjoy » Tue Jun 13, 2017 7:54 am

billr wrote:Give me a hint: who makes that "55505" sensor? Or, post a link to the DS.

Sorry, it is the (Littelfuse / Hamlin / Probably Other Brands) linked to earlier

billr wrote:Are you spinning a toothed wheel in front of it, while bench testing? That sensor doesn't specify that it is a "zero speed" sensor, just waving a target in front of it might not work.

I am. Admittedly I was originally testing it like a ferrous metal detector, but did try spinning my 36-1 wheel in front of it to the same result.

dontz125 wrote:I'm away from my desktop; does the datasheet specify a minimum speed or frequency?

It doesn't, only the max speed. I feel like this datasheet is somewhat lacking. The Hamlin DS has exactly the same data, just rearranged into a different design.

dontz125 wrote:If you aren't a) holding the test piece too far away, or b) using non-magnetic stainless / aluminum / etc, then it sounds like a bad part.

It is bad, confirmed by Littelfuse tech support. Just the luck of the draw I guess! These sensors are ESD sensitive but not packaged by Mouser correctly which may have done it. I will pursue a replacement from them but in my experience this is like pulling teeth.
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Re: 55505 geartooth sensor bench test - bad sensor or bad me

Postby billr » Tue Jun 13, 2017 1:19 pm

Agreed, that DS is rather skimpy. Do you know what the orientation of the sensor relative to wheel travel is supposed to be; got it from some other source? I see white marks on the face and flange of the sensor, but no hint in the DS about what they mean...
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Re: 55505 geartooth sensor bench test - bad sensor or bad me

Postby Mr Bombjoy » Wed Jun 14, 2017 8:40 am

Should be the same as the other flange-mount geartooth sensors others are using.

I think these are just sensor ICs (like the Honeywell SS41C) potted with a custom magnet setup. Those the SS41 datasheets are a little better.

And I have to take back what I said about Mouser - they replaced the sensor without issue!
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