yeah, but the easiest way is to wire 2 AA batteries in series to give you 3 volts.
touch leads to the posts on the gauge and it should go to the middle.
give it a sec as it doesn't react instantly. and then of course swap leads if it doesn't move after a few seconds. lol. always start it backwards, never fails.

To test you need to know the resistance of the sender vs pressure. You also have to have a solid feed from the voltage limiter and a good ground. Any one of the three will affect the gauge reading. The Ralle cluster in my 73 Challenger works fine. But both the oil pressure and temp always are on the low side. The senders are what I believe to be from the original engine. Since the tach and fuel level both function properly I assume the ground is correct. Never checked the voltage limiter. Obiviously it functions as the gauges function. But I wonder if there is an issue there. Or maybe ground offset between the block and the cluster. It just came out of storage yesterday. Been like this since I restored it in 2004. Going to dig into it.
Doug