Bench test fuel gauge?

[Mcstealth]

How do you test a fuel guage?

This gauge reads full with the master on. Tank is not full. I have not yet looked at the float, as it could possibly be stuck in the up position. 

Can I put a multimeter to it and ohm it out? What do I look for?

Thanks

David

[N201MKTurbo]

The floats are 30 ohms each. To test the gauge you need a resistor decade box, or a suitable potentiometer. 

[Fly Boomer]

9 hours ago, N201MKTurbo said:

The floats are 30 ohms each. To test the gauge you need a resistor decade box, or a suitable potentiometer. 

So you would just start at 1 ohm and step through up to 30 while watching the gauge?  Looks like the Cies senders specify 0-5 volts -- what voltage would you hit the gauge with?

[N201MKTurbo]

2 hours ago, Fly Boomer said:

So you would just start at 1 ohm and step through up to 30 while watching the gauge?  Looks like the Cies senders specify 0-5 volts -- what voltage would you hit the gauge with?

To test the gauge, you would need to wire it the way it was wired in the plane replacing the sender with the known resistance. If using a POT, I would measure it with your handheld meter and adjust it to whatever resistance you wanted then put it into the gauge circuit.

I don't have any experience with CIES sensors. I don't know how they interface to the gauge.

[Mcstealth]

3 hours ago, N201MKTurbo said:

To test the gauge, you would need to wire it the way it was wired in the plane replacing the sender with the known resistance. If using a POT, I would measure it with your handheld meter and adjust it to whatever resistance you wanted then put it into the gauge circuit.

I don't have any experience with CIES sensors. I don't know how they interface to the gauge.

As I am a lowly shade tree mechanic, a potentiometer is not something I can just whip out.

[N201MKTurbo]

13 minutes ago, Mcstealth said:

As I am a lowly shade tree mechanic, a potentiometer is not something I can just whip out.

You dont have bins full of them in your closet? I figured everybody did.

You could just order one from DigiKey or Amazon. Get some clip lead wires too, to hook it all up. Should be less than $20 with shipping.

[N201MKTurbo]

You can get a fancy one with a cool knob for less than 10 bucks!

https://www.amazon.com/Onwon-Potentiometer-Wirewound-Multi-Turn-Adjustable/dp/B07MJDLSBQ/ref=sr_1_6?crid=14SGDY9WNYRHH&keywords=Potentiometer%2B100%2Bohm&qid=1701977821&s=industrial&sprefix=potentiometer%2B100%2Bohm%2Cindustrial%2C308&sr=1-6&th=1

 

[Fly Boomer]

2 hours ago, Mcstealth said:

As I am a lowly shade tree mechanic, a potentiometer is not something I can just whip out.

Or one of these:

https://www.ebay.com/sch/i.html?_from=R40&_trksid=p2332490.m570.l1313&_nkw=decade+resistor+box&_sacat=0

 

[Mcstealth]

4 hours ago, Fly Boomer said:

Or one of these:

https://www.ebay.com/sch/i.html?_from=R40&_trksid=p2332490.m570.l1313&_nkw=decade+resistor+box&_sacat=0

 

Okay okay. I get the point!!!

[Pinecone]

On 12/7/2023 at 11:20 AM, N201MKTurbo said:

I don't have any experience with CIES sensors. I don't know how they interface to the gauge.

It depends on what they are interfacing to.  They can be resistance based like stock senders, or voltage or frequency based for JPI, Garman EIS, and some special fuel gauges.

Voltage based supplies 0 - 5 volts over the range of the float movement.  Frequency delivers a 0 - 5 volt square wave output.

 

 

 

[PT20J]

Hmm. It reads zero when disconnected and full s scale when connected. Sounds like the gauge works. Probably a short in the wiring, or a bad float.

[DCarlton]

Anyone happen to know if the OEM resistance senders in the F and J have the same min and max resistance values over their operating range?  And what those values are?  Is it 0 to 30 for all senders?  Same for the planes that have two senders in series?  

Thanks.  

[Jim Peace]

or one of these:

https://www.jpinstruments.com/shop/edm-900-2/

and these:

https://ciescorp.net/products/magneto-resistive-fuel-liquid-level/