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3/24/2021 11:35 AM  #1

Bradster Archive - Gauges - How they Work

Founding Member of the Perpetually Bewildered Society

3/24/2021 12:14 PM  #2

Re: Bradster Archive - Gauges - How they Work

Here's some supplemental information I've found since - maybe it will be useful

Founding Member of the Perpetually Bewildered Society
     Thread Starter

7/17/2021 5:36 AM  #3

Re: Bradster Archive - Gauges - How they Work

While the drawing above is very nicely done, and probably the best description of how it works that I've seen, butĀ  it is not quite accurate. It says that on high the circuit would have 225mA. The IVR (Instrument Voltage Regulator) supplies an average of 5VDC, So using Ohms Law, R= 5V /.225A= 22.22 ohms. Since the sensor is 10 ohms of that total, 22.22 - 10 = 12.22 ohms for the gauge heater. That's a reasonable number, as I have measured 12.4 and 12.8 ohms resistance for the gauge heater.
Here is where the first problem arises- The Ford Shop Manual says that the sensors are variable resistors that range from 10 ohms on high to 73 ohms on low, not 75 ohms. So lets add 12.22 ohms for the heater to 73 ohms for a total of 12.22+73=85.22 ohms when on high. The amperage would then be 5V / 85.22 Ohms = .059 amps, not .006 amps. It looks like they missed it by a decimal point. Its closer to 60mA (.060A) instead of 6mA (.006A).
It may not seem like much, but in electronics it makes all the difference in the world .

Last edited by Mach1Driver (7/17/2021 12:42 PM)


7/21/2021 12:06 AM  #4

Re: Bradster Archive - Gauges - How they Work

Hey Terry, welcome to the forum. This place has THE friendliest people, bar none. Btw, I used to be rpm here, but a couple of bearing issues fixed that.

Bob. 69 Mach 1, 393W, SMOD Toploader, Armstrong  steering, factory AC.

7/22/2021 5:41 PM  #5

Re: Bradster Archive - Gauges - How they Work

Bearing Bob...ok, gotta remember that- I like your RPM avatarĀ 


Board footera

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