gunderse%croc.utah.edu@cs.utah.edu (Eric Gundersen) (07/20/90)
References: <5907@videovax.tv.tek.com> <4145@ash31.UUCP> <3861@kitty.UUCP> Sender: Eric H. Gundersen (gunderse@cs.utah.edu) Organization: University of Utah CS Dept Keywords: Digital Scales Subject: Re: Electonic scales question... >stress will most likely cause an erroneous weight reading due to >spurious stress and/or deformation imparted upon the spring mechanism >and/or LVDT or load cell in the case of an electronic scale. In regards to the hum mentioned in the first aricle, I took apart our GE dig. scale at home and took a look. Its "load cell" (or whatever you want to call it) consisted of 2 parallel stretched wires with a thin metal strip placed across these wires. At each end of this metal stip there was a coil that was connected to the electronic circuitry. When the scale was turned on by standing on it, the metal strip vibrates (like a paddle laying across a rocking canoe. A lever system stretches the wires so that the tension of these supporting wires is proportional (or at least related) to the pressure on the scale. Anyway the final effect is that the frequency of this vibrating strip varies depending on the weight on the scale. Most probably one of the coils forces this vibration and the other is a sense coil. It seems that the digital stuff (mostly built into the LED display module) is just a frequency counter sort of circuit. Looks like someone did some real engineering to make it work. Just thought it might be of interest. Eric Gundersen PS my scale also says not to use it on the carpet. I wondered why it said that too.
browns@iccgcc.decnet.ab.com (Stan Brown) (11/27/90)
In article <27836@mimsy.umd.edu> terry@brillig.cs.umd.edu (Terry Gaasterland) writes to ask about halogen lamps. In article <JON_SREE.90Nov20113948@world.std.com>, jon_sree@world.std.com (Jon Sreekanth) writes: > Local department stores (Boston area) sell them for ~ $100. Damark, among > others, lists them in their catalog for $39.99 (extra bulb set for $12.99), > shipping is $9.50. I bought two from them, and I've been using them since > mid-July, and I'm quite satisfied with them. Warning: a couple of months ago there was a _long_ thread in this newsgroup about problems with Damark. (I am one of the persons who had such problems.) Your experience may be good or bad. Please do not attribute these remarks to any other person or company. email: browns@iccgcc.decnet.ab.com Stan Brown, Oak Road Systems, Cleveland, Ohio, USA +1 216 371 0043
mcginnis@kuhub.cc.ukans.edu (12/28/90)
> > In article <1990Nov28.203618.7294@arcturus.uucp> graham@arcturus.uucp (Thomas D. Graham) writes: >> >> I have some methanol, but I suspect that it is >> contaminated with water. Could I simply take a small sample, say 2 oz, >> burn it and the remaining liquid is water?? Any ideas??? Thanks. > > If you put it in the freezer, wouldn't the water percipitate out as ice? Alcohol and water mix to form a solution with a lower freezing point than either substance by itself. I believe that the ratio that has the lowest freezing point is known as the "eutectic". If you have a non-eutictic mixture and cool it, you will see crystals precipitate out. If you have too much water these will be mostly-water ice crystals, if you have too much alcohol these will be mostly-alcohol ice crystals. Just before the last of the mixture freezes the remaining liquid will be a eutectic mixture of alcohol and water. You could do a rough purification to separate the water and alcohol by cooling the alcohol-water mixture and lifting out the frozed alcohol so long as you didn't let the temperature get too close to the eutectic temperature (and you were sure you only had a little water in the mixture). This would not be an efficient way to separate the two and probably would be less efficient than distillation... just buy some new alcohol.
ekenberg@paris.hep.anl.gov (Tor Ekenberg) (01/23/91)
If I am interested in designing and building my own radar detector, how can I find out about the frquencies that it needs to detect? Any pointers to books or articles dealing with this would be appreciated. TIA.