Last week from Jaycar I purchased a QP5570 3.5 digit LCD panel meter. I cannot get it to operate in a common ground application. I require it to be a 200 mV voltmeter. The instructions and box that it came in say it can be used as a common ground meter but do not say how. Can anyone please assist?
Regards Glenn
-- Posted via a free Usenet account from http://www.teranews.com
been there, done that (as in had_that_problem) and discussed it at length with their technical person (Fred). I have emails and a hand-drawn schematic of his efforts to get a true common negative configuration to work.
Basically it can't be done. Front up back at the store and get a refund. If they get diffcult about it, ask them to demonstrate how to achieve the described result.
Not sure if they are the same meter, but I have bought a couple of the Q2220 meters from DSE - these come with a diagram of how to achieve a common ground application
I could scan the circuit if you want to have a look at it as it might work for the jaycar unit
David
The DSE circuit uses a pair of 7805s driven by a bridge rectifier
David
If ti shows a resistor network between the - and "ground" then it won't work as a true common ground. The Jaycar behind-the-scenes tech bloke confirmed it does require a slight negative bias to be able to operate properly. A true common ground system would require ONLY a scaling resistor divider, with the - and ground terminals directly connected.
ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.