Original poster: Ed Phillips <evp@xxxxxxxxxxx> Tesla list wrote:
With voltmeters that will work OK - ideally you should use a full-wave rectifier bridge of output voltage rating at least twice the voltmeter full scall reading (for safetly); you'll have to play with the "multiplying resistor" in series with the meter. In the case of the ammeter life gets a LOT more complicated. The typical full-scale voltage drop for an ammeter is 50 millivolts and, while you can use a rectifiier as above, but with suitable current reading, its voltage drop will be nearly 1.5 volts full scale so the power lost in the ammeter (and dissipated in the rectifier) could get pretty large. With ammeters there's usually an internal shunt between the terminals and a calibration resistor in series with the meter - the calibration resistor and meter are connected to the terminals of the shunt.Original poster: "Gerry Reynolds" <gerryreynolds@xxxxxxxxxxxxx> Hi Gregory,I would think you ought to be able to modify them to work. Something like a rectifying diode, resister, and capacitor (if needed). You will need to recalibrate them with the resistor value easy to compare to a DMM.Gerry R.Original poster: Gregory Morris <gbmorris@xxxxxxxxx> Hi,I'm wondering what is the best source for voltmeters and ammeters (such as for a control panel)? They probably come up on e-bay on occasion, but is there any sure source that coilers like to use or find work well?I have a DC ammeter as well as a DC voltmeter from an old piece of equipment, but I suspect that it's probably not possible to convert them to AC...is it?Thanks, Greg
Ed