Well I spoke to my instrument guy (dad) to confirm 100%.
He agrees with me, the VDO ammeter is a moving coil instrument and can easily be converted to voltmeter. His comment was why would you want to, and we discussed the shunt size etc as has already been covered.
After a short discussion we came up with the folowing options.
To leave as an ammeter:
1) get another GTS dash and cut the shunt out and place in parallel with the current movement.
2) The shunt current is not the maximum current the shunt can handle and would be well under maximum power rating, so would easily handle the 80 amps (double the current would produce 4 times the power but we estimate the power consumed by the shunt would be as low as 8mW, so would become 32mW). So remove one leg of the movement from the shunt, measure the resistance of the movement with an accurate low reading ohm meter or wheatstone bridge, then place a resistor of this value in series with your movement (between the open leg and the shunt) 1/4 watt would be more than adequate.
3) Measure instrument resistance as pointed out above, plus measure full scale deflection current of movement. Send this info to any reputable instrument place and they will send you an 80A shunt to suit the meter, replace your 40A shunt with this.
We also believe that your 80A alternator is not likely to put anywhere near 80A into the battery (ammeters ony read charge and discharge current of the battery, not alternator current).
Convert to voltmeter:
VDO moving coil meters are sealed and the shunt shall be external to the movement, remove the shunt and place a resistor in series with the movement. The needle is pressed on so can easily be removed and place further to the left.
Information from Nepean instrument services, which ceased operation many years ago. He was the VDO service agent during the late 60s early 70s.
final note, dad remembers having a new guage set for an HT/G GTS dash, from when my brother had his HG, not sure which side, he is going to have a look to see if he can find it. If he does and it is the left side I shall open it up and convert it, with pictures for you.
Warren
Edited by user Sunday, 28 March 2010 5:00:31 AM(UTC)
| Reason: Not specified