Hmm, it's hard to say what exactly is happening. There are a few possibilities.
When TouchDRO is used with iGaging scales, it simply passes the reading from the scale (Chinese capacitive scales keep track of the position internally). There is no mechanism for the TouchDRO adapter to lose the position since it doesn't "remember" it. I think you are describing at least three different problems, so let me try to separate them:
The momentary jumps that return to normal are pretty common. If you are interested in the details, look at the "Momentary Large Jumps" in my last blog post:
Common iGaging EZ-View DRO Problems. All iGaging scales do that, but it can also be caused by really bad noise or bad connection. In your case I wouldn't call it normal, so let's assume this is a real problem.
Scale losing its place sounds strange. I haven't seen this happen, but there are a few different places where this can be coming from. The worst-case scenario is a full reset of the scale. iGaging scales don't lose their position immediately after you disconnect them from power. It takes a few seconds to as much as a few minutes before the scale resets to 0. To verify this, plug your scale into the original display, note the position, unplug it, wait for a couple of seconds, and plug it back in. The readout should not change when you plug the scale in. If this is the case, the reset would require a momentary reversal of the power supply voltage. That can happen when you have a giant ground loop (i.e. machine's body ground is many feet away from the TouchDRO adapter ground). You can fix this by isolating scale frames from the machine, but try powering the TouchDRO adapter from a battery pack (or even from the tablet via a USB port) temporarily and see if there is any change.
Scale permanently losing the position can be due to a reset as well. Older scales did that when a stray glitch threw off the data clock, but I haven't seen/heard of EZ-View scales doing that (the reading head seems to have logic that resets the clock after a short timeout).
Scale losing its place when you shut down [the adapter, I presume] is normal. These are not absolute scales, so they keep track of the position by counting from the place where the scale was powered up. There is no harm from leaving the TouchDRO adapter running 24/7. It consumes less than 1W of electricity when active, and even less when idle. (if this is different from what your problem is, please let me know).
My guesses would be as follows (in the order of likelihood)
1. There is something wrong with the scale itself
2. There is a grounding problem or serious noise problem that creates large pulses in the cables
3. There is a connection problem between the scale and TouchDRO. Try plugging the scale into Y input and see if anything changes. I've seen very similar behavior once when there was a crack in the solder joint under the MicroUSB connector on the TouchDRO board.
in short, this is not normal. iGaging scales have a few issues, but once you start losing position, something has to be broken. If the scale is easy to remove and you'd be willing to send it to me, I can hook it to the scope and see if I can find any problems. If it's defective, I can swap it for a good one (I need bad scales for testing; good ones are easy to come by...).
If you decide to upgrade the scales, pretty much any Chinese glass scales are going to be a huge step up. The difference between the very cheap ones and "mid-range" is in the electronics (better scales have better-built circuit board) and support. The glass and the "carriage" are all identical, and they all use the same LM339-based circuit. Cheap ones use single-sided through-hole PCB with one or two capacitors, while the better ones use a surface mount PCB with a few ceramic bypass capacitors and series resistors. In practice, I have noticed any difference in performance.
Thank you
Yuriy
