No, but it seems that the amount you refill in a trough or bucket is pretty consistent . That was what I didn’t like about auto waterers. Even though they are convenient you really have no idea how much anyone is drinking.
That is why you use an auto waterer with a meter. With our Nelson’s we lose much less water than an open heated trough so I have very accurate numbers of what more horses are drinking.
I’ve got a Nelson (the older 300 Series) that was here when we bought the place. It’s been good but due to a few minor things I don’t like if it ever dies I’ll probably replace it with a Jug Waterer. https://www.bakkoindustries.com/jug-waterers
For the open bowl type you need to have protection from the wind or they can ice over (not necessarily freeze solid) in certain conditions as I found out. Granted this happened during the Polar Vortex a few years ago in MN when we had a sustained -50F windchill, so pretty much everything iced over. 
Nelsons. Our former barn owner (we were there almost 20 years) installed them outside about 15 years ago. About half the horses there are outside 24/7. We are in southern Maine. They are reliable and freezing wasn’t a problem even when it got down to -0- or below. DH had parts so he could replace a heating element or anything else. I used to check the one where my horse was when I turned him out.
We moved last November to a barn where he has a stall with attached run out. Nelsons in all of the stalls. No problems there either. Bowls are removed, emptied and wiped out daily as part of mucking duties. Runs are also picked daily. He’s 27, loves it there.
