Calibrating Temperature Gauges

[JohnD]

I've posted before about calibrating a temperature gauge, by setting it up on the bench with a pan of water on a camp stove.

 

 

That at least tests the whole system, but as an alternative method over on the US site The Triumph Experience, Tony M from BC, Canada, has written about electrical calibration.

He quotes the specific voltages that should be applied to the gauge, and shows the reference marks that the needle should achieve.

You would need a bit of kit to apply those voltages, but Interesting and useful.

 

 

See: http://www.triumphexp.com/phorum/read.php?9,1405143

 

John

Edited October 10, 2016 by JohnD

[oldtuckunder]

Interesting.

 

Just wondering if testing  a sender gauge combination in the conventional hot water method if one should also include the voltage stabiliser?

 

Alan

[JohnD]

Of course!

See my pic above!

John

[oldtuckunder]

Of course!

See my pic above!

John

 

Whoops, sorry didn't have the glasses on!

[spitfire6]

Hi John,

 Interesting stuff. I seem to remember you had posted some similar tests concerning the gauge or sensor.

 

I always assumed that the meter is a current operated device, so is it possible you can fill in the blanks and provide:

 

• Resistance of the meter if this is a constant.
• Current draw of meter if this is a constant.
• Voltage to meter VS measured temperature.
•  

With your help, I will be able to:

 

1. Check if the readily available two wire sensors are compatible with the Triumph gauges.
2. Check if the Triumph gauges are compatible with the after market sensors.
3. Make a board that puts the gauge chassis at -3v, so a 0 to 5v signal reads correct, (if the meter is not current driven).

Thanks & cheers,

Iain

Edited October 10, 2016 by spitfire6

[Nick Jones]

Gauges are a heating element wrapped around a bi-metallic strip - not sure whether you'd consider that current driven?  Certainly they are an "average reading over many seconds" device.

 

Nick

[spitfire6]

Hi Nick,

 So the gauge is neither a constant current or constant resistance gauge? That screws things up a bit with modern technology. PWM to the rescue, maybe.

Thanks,

Iain.. 

[JohnD]

Thank you, Nick!

 Yes, Iain, they rely on the simple heating of a bimetallic strip by the current in a coil, which automatically damps the response of the needle to vehicle movement, and surge.

A clever, if antiquated technology, that also makes the so-called "voltage stabiliser" work, in that it is nothing of the sort, just chopping the battery voltage on and off to produce an average 10V, too quickly for the gauge to respond.    And by use of another bimetallic strip!

 

John

[JohnD]

double post deleted

Edited October 11, 2016 by JohnD

[oldtuckunder]

double post deleted

 

Nothing to worry about your were talking bimetalic 

[Nick Jones]

Yep, they are clever things. Whenever I look inside one I marvel at how something so crude can actually work so well. The same tech is used on some pretty modern stuff too.

 

Nick

[spitfire6]

Hi,

 Found JohnD's temperature (KOhms to C) graph.

 

Cheers,

Iain.

 

 

[spitfire6]

Hi John,

 Do you have the raw data for R vs Temperature? I am trying to simulate but over 40c things are a little cramped.

 

Thanks in advance,

Iain.

[JohnD]

It would take me some time to find the list of temp vs Ohms, as I did it many years ago now.

"over 40c things are a little cramped."

Do you mean that the temp is rising too fast to get a reading?

 

My setup was a pan of cold water over a camp stove, and if I did find the water was heating too quickly (I don't remember) I would have turned down the gas!

OR, used a bigger pan.

 

Delighted you are doing it again, looking forward to some new figures, ready with defence if they don't match!

JOhn