So the current meter had me stumped. At first I thought it may be the charger for the battery, but, nope. Next I thought it had something to do with the fact I was running off upstream shunt side of ground. Switching to a direct ground connection didn’t help either. However, in the process of trouble shooting I figured out that if I ran the meter off an isolated supply, it worked perfectly.
Even though these meters were supposed to have a common ground, in this case at least it seemed to be causing more problems then it was worth. Solution, isolated power supply. The DC switcher that I was using to power everything else didn’t have an isolated ground and looking around on line the only circuits I found where for supplying just a few milliamps from a 555 or other square wave to voltage shifter type of circuit. I could order an isolated supply but by the time I paid for shipping it was going to cost more then the meter itself.
Eventually I stumbled on a post at the Back Shed, THANK YOU!!! I dug around in the parts bin an WhaaaLa, an old Ethernet card and a 5v to 9V isolated stepper was mine. I added a little TO92 style linear 5V regulator and now it goes 5V –> 9V –> 5V isolated. Its not the most efficient animal in the world, but, it was free and it works, perfect current measurements are now mine to see.
Shweeeehewwww, goes to show you sometimes, when you buy things to make your life easier, they may actually not. Here is a picture of the finished isolated 5V supply. Be sure to check out he link to the Back Shed if you want more info on how it was built.
