From: n1khbjoe Sent: Saturday, October 02, 2004 5:23 PM Subject: [FT817] voltmeter Hello 'packers, I have found a new (to me, anyway) item at Walmart with potential for portable ops. It is a 2.5 digit digital voltmeter made for automobile use. It is Innova #3721 located in the automotive dept. and priced at $14.77 here in Conn. (though they were hanging on a peg that said ~$8). The unit consists of a cig lighter plug attached to a swiveling DVM so that the display can be viewed from various angles. It both measures and draws operating power from the same receptacle, and so there is aprroximately 20 ma being drawn during useage according to the jumpy readings on my digital multimeter. There are also LED's, display graphics and other info on the unit which purport to convey information on battery status as it applies to automotive starting ability. Most of this can be ignored and only the straight voltage reading would be of use for hams using batteries in portable use because of differences in interpretation of starting ability vs. lighter loads encountered for ham and other use. I will investigate more on this unit soon such as the possibility of removing the cig lighter portion of this unit so that clip leads can be attached. On this note, I did in fact find another Innova companion product on the web with model #3720 that comes this way, but I don't know where it is sold. I will also check accuracy, but the readings did follow the readings on my $10 cheapie digital mulimeter within .1 volts or so. Could be a good dedicated permanently attached addition to gel power packs for portable ops. I'll post more later, but interested to hear from others who may have/will use this unit. Joe N1KHB ========================================================================== Date: Sat, 2 Oct 2004 22:19:55 +0200 From: "i2jjr" Subject: Re: voltmeter Hi Joe, I normally use a sort of this but homebrewed: I bought a bargain LCD panel voltmeter kit , 3.1/2 digit, and add some resistor to calibrate it for 19.99 V full scale and for its 9V supply. I also have a shunt resistor that allows me to read the current flowing thru the meter small housing, for 10 A full scale ( come from junked tester). So I have this small box having two input terminal for the battery and two output to the load, plus small switches for test-on and V-I readings. The only thing I would do different, is to add more output terminals and more switches to select the measure to do, one for trx, one for tuner, one (only output) for LED lights, ore for batterycharger or solar panel input. In this way I could have a complete "walking-station" tester. I plan to incorporate such a thing into my next battery pack using D 9500mAh cells or perhaps F 13000mAh cells. It will be a bit larger than the Z11 itself, so I will pack all togeter with a velcro ribbon. 73 de Augusto i2jjr ========================================================================== Date: Sat, 2 Oct 2004 19:20:07 EDT From: N1KHB@aol.com Subject: Re: voltmeter Hi Augusto and others, I too have thought of homebrewing voltmeters - I have two Modutech DPM modules next to me as I write this in fact. But for a midteens price tag, I thought that it still might be attractive for some as it was for me being already built. BTW, it ocurred to me after sending the original "voltmeter" post, which I wrote in haste, that it might be interpreted by some that I meant to imply that it would be ok to leave a 20 ma draw constantly connected to a battery. I did not of course, so I clarify here by saying that the voltmeter would either need to be switched (momentary to read, for instance or switched on when battery is in use, etc.) or be in in a setup that always goes back on charge whenever it is not in use. If not, a 7 ah gel would become discharged after a couple of weeks. It isn't perfect - but what is? 73,Joe N1KHB ========================================================================== ========================================================================== ========================================================================== ========================================================================== ========================================================================== ========================================================================== ========================================================================== ========================================================================== ========================================================================== ========================================================================== ========================================================================== ========================================================================== ========================================================================== ========================================================================== ========================================================================== ========================================================================== ========================================================================== ========================================================================== ========================================================================== ========================================================================== ========================================================================== ========================================================================== ========================================================================== ==========================================================================