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Discussion Starter #1
hi everyone, Im trying to calibrate the speedometer in my '83 GTV6 with the early sending unit and cant remember how many teeth are on the shaft inside the transmission. The reason one needs to know this information is so that I can calculate the frequency to feed the speedometer head to perform the calibration at differernt speeds.

I know for a fact that when I calibrated my Milano's speedometer there was 6 teeth on the shaft, which makes it easy to figure out how many pulses/km its supposed to be...

If anyone knows if the early transmission shafts were different number of teeth please let me know, so I can get my function generator out and start

thanks!
 

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The speedo should have a label on the back saying how many metres/pulse. That's how I 'calibrated' mine with a signal generator. Beware however, the head unit is not very accurate accross the full range.
 

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the Veglia speedometer requires 100 pulses per minute per indicated mph. In other words, a pulse rate of 5500ppm will make the speedometer read 55 mph.

From post #15 of Speedometer amplifier
 

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the Veglia speedometer requires 100 pulses per minute per indicated mph. In other words, a pulse rate of 5500ppm will make the speedometer read 55 mph.
Using a stop watch, I calibrated mine to act like you describe: Using 80MPH (130km/h), you should have a frequency of 8000/60 = 133Hz. With a stop watch and resetting the odometer, I found the accumulated mileage to be 5% slow at this setting, which is very close in my opinion for 40 year old tech. I then tuned the D'Arsonval current gain in the instrument using the trimmer and adjusted the weights on the arms of the movement to account for my custom made needle throughout the entire range. The instrument is very good now. I may possibly re-calibrate the instrument to get rid of the low reading odometer but for tonight's drive it was very good
 
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