Marcus has very practical suggestions. If you really want to measure voltage, just use a voltage divider -- two resistors in series and measure the midpoint voltage.
For instance, 10K Ohm resistors will allow 12V/2*10^4 = 0.6 mAmp current with a midpoint voltage of 6V (or so, the bttery voltage might start a little higher). The DS2438 can measure 2-10V easily and draws 50uA so should work for your analysis. In fact, the DS2438 is a battery monitor and can measure current draw. It's sensors (Vsens) actually measure a voltage differential of up to 250mV. So measuring voltage across a 1 Ohm resistor in series with the load can give current readings up to 1/4 amp. See DS2438 datasheet: http://datasheets.maxim-ic.com/en/ds/DS2438.pdf and OWFS man page: http://www.owfs.org/uploads/DS2438.3.html On Thu, Jun 16, 2011 at 2:08 PM, Markus Gaugusch <mar...@gaugusch.at> wrote: > On Jun 16, Jason C. Lamb <l...@gweep.net> wrote: > >> I am fairly new to 1-wire, though I setup a temperature probe about 4 years >> ago with excellent success. Today I am looking to 1-wire to monitor the >> voltage on my car battery. It seems to drain over night. I can measure the >> voltage at night using a multi-meter (13.1 VDC) and by the morning it is 0.2 >> VDC. The problem I am not sure if the voltage drop is slow and steady, or >> there is a defect in the battery that is causing a sudden drop off. > > While this is not a 1-wire solution, I'd rather pull some fuses of > suspicious consumers (like radio) and see if the problem persists. If you > know which fuse is relevant for the battery draining you can find the > problem more easily. > > Additionally, you don't need a voltage meter but an ampere meter to > measure the current. Voltage won't tell you how much power is consumed > (it will only tell you when the power is over, that's it). > > But: This is more dangerous, as you have to put the ampere meter in-line > with the consumer, and not parallel like a voltage meter. Some devices > suck significant amounts of power, so be prepared for some sparks to fly! > > I'd probably pull out a fuse, and put in an ampere meter instead. Another > suspect (apart from the radio) is any consumer in your doors. The cables > there tend to loose their insulation over time and can cause more or less > significant current flow. > > > best regards, > Markus > > ------------------------------------------------------------------------------ > EditLive Enterprise is the world's most technically advanced content > authoring tool. Experience the power of Track Changes, Inline Image > Editing and ensure content is compliant with Accessibility Checking. > http://p.sf.net/sfu/ephox-dev2dev > _______________________________________________ > Owfs-developers mailing list > Owfs-developers@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/owfs-developers > ------------------------------------------------------------------------------ EditLive Enterprise is the world's most technically advanced content authoring tool. Experience the power of Track Changes, Inline Image Editing and ensure content is compliant with Accessibility Checking. http://p.sf.net/sfu/ephox-dev2dev _______________________________________________ Owfs-developers mailing list Owfs-developers@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/owfs-developers
