I actually checked the voltage on the gauge input wire for sender just to see what it reads. It read 5v when the gauge was powered on in 12v system

I thought so. (Post #15)
You'll be able to use mine or @Irving 's circuit to parallel two gauges, provided that they are both the same type. If one is an ordinary analogue gauge, you won't easily be able to parallel a digital one.

 

I thought so. (Post #15)
You'll be able to use mine or @Irving 's circuit to parallel two gauges, provided that they are both the same type. If one is an ordinary analogue gauge, you won't easily be able to parallel a digital one.

They are both digital. One is only 5 long bars vs probably 12 smaller bars but both same higher resistance but one is 11 ohms on lower end and other is 33 at lowest.

 

I thought so. (Post #15)
You'll be able to use mine or @Irving 's circuit to parallel two gauges, provided that they are both the same type. If one is an ordinary analogue gauge, you won't easily be able to parallel a digital one.

I apologize, I’m not nearly as adept as either you or @Irving. So, I will need some additional parts? Or just wire it in parallel? When I was testing both gauges at same time, I split the sender unit wire from the tank and sent it to both sender input wires on each respective gauge, while each gauge had its own circuit for 12v power and likewise, each gauge has its own ground. In effect, each gauge has 3 wires. 12v+, Ground, and sender wire which appears to be 5 v when gauges are powered up. I thought wiring it this way is in parallel. Again I apologize for being so green on this. In fact, I would pay you or Irving to build whatever I need with terminals I could connect my sender leads on gauges to, so it would make them rRad the same. I had to buy a little tach adapter as well. If it could be built really small, I could mount it in my fairing, tucked out of sight. I’d pay you a reasonable price. Interested? Thanks so much for your help.

 

This forum doesn't give up so easily!
Are the sender wires on BOTH gauges 5V? If so, it will still work.

 

This forum doesn't give up so easily!
Are the sender wires on BOTH gauges 5V? If so, it will still work.

I will confirm this tomorrow afternoon, but I’m betting they both are 5v. If you run each gauge with same sender separately one at a time, they are reading exactly the same amount of fuel. I test at full, and half tank and in between

 

I will confirm this tomorrow afternoon, but I’m betting they both are 5v. If you run each gauge with same sender separately one at a time, they are reading exactly the same amount of fuel. I test at full, and half tank and in between

I bet they are too. They are obviously both reading the same value from the sender but it doesn't necessarily follow that they are both using the same method to read it!

 

I bet they are too. They are obviously both reading the same value from the sender but it doesn't necessarily follow that they are both using the same method to read it!

I read up a little on op-amps. I want to try this method. Can you tell me which one to buy? Is everything I need in the one piece or will I need anything else? Thanks

 

I read up a little on op-amps. I want to try this method. Can you tell me which one to buy? Is everything I need in the one piece or will I need anything else? Thanks

Do you have a reasonably accurate multimeter wth an Amps range? If so, can you try this:

With just 1 gauge in circuit, measure the voltage across, and current through, the sender - On 20volts setting measure from sender feed (red) to ground (black), then disconnect sender from gauge, adjust multimeter to Amps setting (and you usually have to move red wire from V to A hole in meter - no sniggering at the back there) then measure current with black probe on sender, red on gauge. Repeat for gauge 2 (not forgetting to put red wire on meter back to do volts reading) and again for both gauges in circuit. You may have to use milliamp (mA) setting if A range gives a very small number. If you can do that for more than 1 fuel level then great, but not essential.

I'll come back with opamp details once we have the results of that test...

Where are you based?

 

Do you have a reasonably accurate multimeter wth an Amps range? If so, can you try this:

With just 1 gauge in circuit, measure the voltage across, and current through, the sender - On 20volts setting measure from sender feed (red) to ground (black), then disconnect sender from gauge, adjust multimeter to Amps setting (and you usually have to move red wire from V to A hole in meter - no sniggering at the back there) then measure current with black probe on sender, red on gauge. Repeat for gauge 2 (not forgetting to put red wire on meter back to do volts reading) and again for both gauges in circuit. You may have to use milliamp (mA) setting if A range gives a very small number. If you can do that for more than 1 fuel level then great, but not essential.

I'll come back with opamp details once we have the results of that test...

Where are you based?

I’m out of Huntington West Virginia. I can definitely perform this test. I work nearly every day but tomorrow I work half day so I will do this once I get home. I do have to prep for a colonoscopy tomorrow too but I can do the test between trips to bathroom lol. (It’s ok to laugh at this one). I keep up on this because I’ve lost my brother, mother, and father to cancer. Only have a sister left and I’m just early 50s. I will report the results soon as I get them.

 

to prep for a colonoscopy tomorrow

No laughing matter - been there myself with added complication of no sensation from chest down and stuck in a wheelchair... brown Niagra my carer called it!...sorry for your loss, I lost my mother to rectal cancer at the too young age of 62, same age as I am now... so no arguments from me, far too important...

 

This is the basic buffer circuit.



The challenge is to find an op-amp with sufficient current output (>100mA), >13V supply, and in a package that is easy for you to work with.

 

This is the basic buffer circuit.

View attachment 244376

The challenge is to find an op-amp with sufficient current output (>100mA), >13V supply, and in a package that is easy for you to work with.

Sounds simple, but it may be complicated by having to get the output quite close to zero to indicate "full".

 

The challenge is to find an op-amp with sufficient current output (>100mA), >13V supply, and in a package that is easy for you to work with.

There are a few options but most are silly money. An opamp/MOSFET combo is far easier to source and cheaper and a no-brainer IMHO. If the current readings that the TS comes back with are sub-50mA as I'm expecting then a cheap DIP opamp and a 2n7000 is a workable option...

Sounds simple, but it may be complicated by having to get the output quite close to zero to indicate "full".

The opamp/MOSFET gets around that nicely...

 

Sounds simple, but it may be complicated by having to get the output quite close to zero to indicate "full".

Approx 35mA x 11ohm = 385mV. Should be OK for most RTR opamps if you can find one with >50mA sink capability.

Reading up further on these aftermarket devices there is limited evidence they are voltage driven ratiometrically from the supply rail measuring the actual voltage aross the sender, so voltage-driven rather than current-driven, in which case the full reading will be most impacted by two in parallel (as TS indicated).

 

Hello,

Have a look at the attached list for opamps with a higher current output as 100 mA.

Bertus

 

Hello,

Have a look at the attached list for opamps with a higher current output as 100 mA.

Bertus

Thanks, a useful list. Though I have some of them, knowledge is power

 

Thought about putting all four stages of an LM324 in parallel, but I remember that the LM324 hasn't got much output current below 600mV.

 

Do you have a reasonably accurate multimeter wth an Amps range? If so, can you try this:

With just 1 gauge in circuit, measure the voltage across, and current through, the sender - On 20volts setting measure from sender feed (red) to ground (black), then disconnect sender from gauge, adjust multimeter to Amps setting (and you usually have to move red wire from V to A hole in meter - no sniggering at the back there) then measure current with black probe on sender, red on gauge. Repeat for gauge 2 (not forgetting to put red wire on meter back to do volts reading) and again for both gauges in circuit. You may have to use milliamp (mA) setting if A range gives a very small number. If you can do that for more than 1 fuel level then great, but not essential.

I'll come back with opamp details once we have the results of that test...

Where are you based?

I found this in an online manual which is specifically for the sending unit I have in this circuit. I’m attaching a screenshot of the resistance readings for full and empty. They are both a bit lower than my gauge but the travel difference between empty ohms and full ohms readings is almost identical with both gauges 11 to 219 ohms for stock oem gauge and sender, and 33 to 240 ohms on my intellitronix. Though there is a difference, the gauges read the same. Or very close to it.

 

I'm wondering because the voltage of the OEM and the I* guage is the same, use an I-V converter in the OEM circuit and for the I* guage, use a voltage controlled current source or sink.

You essentially make the same current flow in the other guage with a fixed resistor.

It is about 450 mA for 11 ohms and 20 mA at the 240 ohm end. Those values make the design "difficult".

 

Do you have a reasonably accurate multimeter wth an Amps range? If so, can you try this:

With just 1 gauge in circuit, measure the voltage across, and current through, the sender - On 20volts setting measure from sender feed (red) to ground (black), then disconnect sender from gauge, adjust multimeter to Amps setting (and you usually have to move red wire from V to A hole in meter - no sniggering at the back there) then measure current with black probe on sender, red on gauge. Repeat for gauge 2 (not forgetting to put red wire on meter back to do volts reading) and again for both gauges in circuit. You may have to use milliamp (mA) setting if A range gives a very small number. If you can do that for more than 1 fuel level then great, but not essential.

I'll come back with opamp details once we have the results of that test...

Where are you based?

if I’m doing this right, it appears the voltage is 1.93 volts on oem gauge and tank full or very close to it (gauge reads full). The intellitronix gauge shows 2.41volts when it’s hooked to same sender. Each one was hooked up by itself. Now, apparently my little greenlee meter won’t read dc current or possibly, it won’t read low enough? My lowest setting for dc current is 20m.