G oog le BadWeB | Login/out | Topics | Search | Custodians | Register | Edit Profile

Buell Forum » Knowledge Vault (tech, parts, apparel, & accessories topics) » Do It Yourself: Machine Shop, Garage, Tools and Tips » How does a thermistor low fuel detector work? « Previous Next »

Author Message
Top of pagePrevious messageNext messageBottom of page Link to this message

Reepicheep
Posted on Monday, July 27, 2015 - 07:46 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

I always wondered how the thermistors detected low fuel, so I thought about it and googled it.

Basically, the principal appears to be to try and "heat" the thermistor. If a thermistor is in an assembly covered in a liquid, it will be much harder to heat than if it is in an assembly out in the air.

So whatever ambient is, you can take a thermistor reading, pump a known quantity of heat (current over time) through it, then take another reading. That tells you how much the temperature has increased.

I would have to do some testing and thinking to figure out if the change in temperature would be constant over all ambient temperatures. The resistance change wouldn't be, thermistors are insanely nonlinear, but the temp change might be.

In other words, pump 5mA through a thermistor for 10 seconds and you will get a 2 degree rise in temperatures at 20 degrees ambient. Pump 5mA through a thermistor for 10 seconds and you will get a 2 degree rise in temperatures at 100 degrees ambient.

(Or even if not linear, perhaps the difference is low enough for a binary decision of "in liquid or not").

It would be fun to build one.
Top of pagePrevious messageNext messageBottom of page Link to this message

Tpehak
Posted on Thursday, June 13, 2019 - 10:14 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

I connected my Motogadget low fuel LED light through relay trough the fuel pump thermistor to sense low fuel. It works very good. I do not know how it works in original instrument cluster tho.
« Previous Next »

Add Your Message Here
Post:
Bold text Italics Underline Create a hyperlink Insert a clipart image

Username: Posting Information:
This is a private posting area. Only registered users and custodians may post messages here.
Password:
Options: Post as "Anonymous" (Valid reason required. Abusers will be exposed. If unsure, ask.)
Enable HTML code in message
Automatically activate URLs in message
Action:

Topics | Last Day | Tree View | Search | User List | Help/Instructions | Rules | Program Credits Administration