Gentlemen
...AcuuRemote DRO...The batteries are three volts and I am thinking that I should connect six volts DC to the respective terminals... The next problem would be connecting all three readouts to one Power Supply.
I just checked one of my igaging displays. The batteries on it are wired in parallel, not series. That means you only want to connect to one of the battery locations, and with only 3 volts, not 6 volts. You can easily verify that your DRO is wired the same way by removing one of the batteries and operating with only one battery (doesn't matter which one). If the DRO works, it is wired the same as mine: batteries in parallel, 3 volts.
These batteries, when new, are 3.4v, and if I were doing a battery replacement I'd go for the full 3.4v as I find the display contrast is better with a fresh battery.
Running multiples from one supply: no problem at all. Just hook each of these up to your power supply.
Back to finding the supply: I looked at ebay for "3v dc adapter" and found several "wall warts", like the charger for your cell phone. Make certain that the one you buy is specified as "DC" and 3 volts. As for the current rating, the DROs take very little current and I doubt that it is possible to purchase a charger that provides too little current. The first ebay one I found (see below) is rated at 1 amp - that's probably enough for hundreds of the DRO readouts. If you have a choice, buy the smallest.
It is a little bit of a crap shoot to know just what voltage will really come out of these, but they are cheap, so if you get one that doesn't work out you can just pitch it. See for instance ebay item 140669436689, for $4 from Taiwan. If you get something like that, either get a matching connector from Radio Shack and wire that connector to your DRO system, or cut the connector off and wire directly. But be VERY careful to get plus to plus and minus to minus. Also, but sure to check the charger you get before actually connecting it to your DRO. Just plug it into the wall and measure the tip voltage to make certain it is (a) DC volts and (b) between 3 and 3.5 volts.
Connecting to the battery location: it seems it might be easy to come up with a fake battery with a couple wires that goes into the battery socket and connects to the outer ring connection and the bottom connection. Then the DRO would not be damaged by soldering directly to the battery connector. The wires could come out the back perhaps around a notch in the battery cover so that it would continue to function as well, in case you wanted to revert to real batteries.
Here's another way to do this: use a USB charger, such as ebay item 310499288944 for a buck. Get a USB cable and cut off the end that doesn't go into the charger, and with your voltmeter, find the two wires that have +5v between them. That's too much for the DRO, but we're going to reduce the voltage and get you a light to show that power is on as well:
Buy a 5mm white LED, such as ebay item 320878486780 ($1 for 10). Wire as shown below:
For the resistor, anything from 85 to 100 ohms is ok, and it uses little power so the power rating is not important. The White LED will have about 3.4 volts across it, so that is what regulates the 5volts from the USB adapter down to the 3.4 volts needed for the DRO. Again, the caveat here is to be careful and check both the output voltage and the polarity before connecting this to your DRO display. The advantages of using the USB adapter approach are:
1) really cheap
2) you get an LED to show that power is applied (but of course you would know that anyway)
3) the LED makes a good regulator to ensure you don't get too much voltage into your DRO
The disadvantage of the USB adapter is that if the LED isn't connected for some reason, you would be applying 5 volts to your DRO instead of 3.4, and I don't know whether 5 volts would damage the DRO (I doubt it, but it could).
Good luck with this, and if you work out a fake battery to make the connection to the DRO, please publish that.
bix