[ARC5] Hamfest DVM modules

[jeepp@comcast.net]

    That would be fine except that that there are only three leads on the module.  In fact, one version he had, had only two leads, self powering from the measured source.  
Jeep. K3HVG
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------ Original message------From: Date: Sun, May 8, 2016 11:36To: DSP3;Cc: MRCA at mailman.qth.net;arc5 at mailman.qth.net;Subject:Re: [ARC5] Hamfest DVM modules
Jeep,I believe the power supply ground is not referenced to the meter input ground. You have to power the meter with an isolated supply like a 9 volt battery or from a power transformer secondary.Mike N2MS----- Original Message -----From: DSP3 To: MRCA at mailman.qth.net, arc5 at mailman.qth.netSent: Sun, 08 May 2016 13:10:18 -0000 (UTC)Subject: [ARC5] Hamfest DVM modulesFor what its worth, I bought two of those small, pop-in 3-digit, panel mount voltmeters at the Hagerstown fest, yesterday.  No documentation, whatever, is provided.  The idea was to add them to a couple of LV power supplies I have that are meterless.  Well, they don't work very well, at all, I believe. They are powered by about 3-9v DC.  The ones on display appeared to be just fine.  I wired both of them up to batteries and power supplies and, with proper Vcc applied, got readings typically 20-30% high along with a 2v-4v instability.  I thought that perhaps the meters were responding to noise and/or ripple but the 9v batteries connected exhibited the same error and instability. The meters do appear stable with only Vcc applied and indicate 00.0v.   Anyone have any experience with these little DVMs?  Is additional filtering required?  Are they maybe AC meters with a high crest factor and a bridge on the input?  I have no idea.......Jeep - K3HVG
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