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Analog Bench Voltmeter — Parallax Forums

Analog Bench Voltmeter

LoopyBytelooseLoopyByteloose Posts: 12,537
edited 2014-06-20 23:59 in General Discussion
When I am trickle charging Lead Acid gel cells, I like to leave the Voltmeter connected to monitor progress. But it is a bit annoying to have to replace the 9V battery in my multimeter, so I picked up an analog meter that doesn't require any batteries... something similar to the one below. I have a 0-3 VDC, a 0-15 VDC, and a 0-300 VDC range.

It is a bit crazy how the world has gone over to digital when these meters don't require a power supply and last nearly forever. I paid about $8.00 USD for mine in a nice case and new ... locally of course.

http://www.ebay.com/itm/NEW-United-Analog-3V-15V-300V-DC-Triple-Scale-Educational-Bench-Volt-Voltmeter/321432026147?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222003%26algo%3DSIC.FIT%26ao%3D1%26asc%3D22426%26meid%3D7640665238177293828%26pid%3D100005%26prg%3D9723%26rk%3D2%26rkt%3D6%26sd%3D221462765443&rt=nc

http://www.ebay.com/itm/NEW-3V-10V-15V-DC-Triple-Scale-Analog-Educational-Bench-Volt-Meter-VDC-Voltmeter-/221462765443?pt=LH_DefaultDomain_0&hash=item3390359f83

Comments

  • ercoerco Posts: 20,256
    edited 2014-06-15 10:32
    Or go free power digital for a paltry $1.33: http://www.ebay.com/itm/Mini-LED-DC2-5-30V-Red-Volt-Voltage-Meter-Display-Digital-Voltmeter-Self-Powered-/201098834216?pt=LH_DefaultDomain_0&hash=item2ed26cb128

    It would be interesting to compare current draw between the analog and digital meters. Analog has current flowing through a coil, could be in the microamp range. Digital is powering many LED segments, could be 100 mA or more. Negligible in comparison to the charging current either way.
  • Duane DegnDuane Degn Posts: 10,588
    edited 2014-06-15 12:13
    erco wrote: »
    Digital is powering many LED segments, could be 100 mA or more.

    I just received one of these a few days ago. It looks like it's the same as your ebay version (though I paid more and paid shipping).

    The current the sensor draws depends on how many segments are lit up. The highest current I saw as I turned the voltage up from 3.2V to 19.0V was 13.5mA. The read out on the display always matched my bench top power supply's readout.

    One nice thing about Electodragon, is their shipping can be pretty fast. I'm pretty sure I received my stuff in less than one week from ordering it. I used the DHL shipping option.
  • Ron CzapalaRon Czapala Posts: 2,418
    edited 2014-06-15 16:29
    I had a meter related issue last week. I managed to blow the 440mA fuse in my Fluke 179.

    The fuse cost $6.72 since it is a specialty type (FUSE 0.44A .406X1.375 1000V FAST). http://www.digikey.com/product-detail/en/943121/614-1083-ND/1802035

    I also went to RadioShack and bought a 1 ohm, 10 watt resistor so I could measure the voltage drop across it to measure current rather than blowing another fuse!
  • ercoerco Posts: 20,256
    edited 2014-06-15 17:53
    Duane Degn wrote: »
    ... though I paid more and paid shipping...

    There's one born every minute. Always buy on sale before you need it with free ship. Hoarders #1 rule, Duane Dawg!
  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2014-06-15 23:51
    It seems nobody likes the retro look and feel of an analog meter except me. Ebay has some oldies out there that look very cool and work very well.

    One rarely needs to get their voltage readings down to hundredths of a volt. And I think the analog meter's current draw is something in the microampere range. It can monitor a battery in a standby state and not drain it down.
  • Mark_TMark_T Posts: 1,981
    edited 2014-06-16 06:40
    The reason analog voltmeters are dead is their disgraceful performance. 20k ohms per volt means you
    just cannot measure in-circuit voltages accurately without always correcting for the circuit impedance
    (or put another way they conduct 100's of uA from the point you are measuring).

    Typical DMMs are 10M input impedance, ie a fraction of uA in a typical measurement...

    However for monitoring charging lead-acid batteries a few 100uA is neither here-nor-there
    so they are perfect for the job. There are lots of little voltmeters on eBay for a few £/$ that
    power themselves from the voltage they measure (designed for monitoring RC LiPo batteries
    I think), which are another option.

    [edit: for instance http://www.ebay.co.uk/itm/RC-Voltage-Lipo-Battery-Meter-Tester-Indicator-2-6-cells-LED-Panel-Voltmeter-T5-/390643128721?pt=UK_ToysGames_RadioControlled_JN&hash=item5af4251991 ]
  • TorTor Posts: 2,010
    edited 2014-06-16 06:49
    But it's not analog vs. digital, it's powered vs. non-powered voltmeters. Back in 1976 I bought an analog FET-VOM, and I still own it. Field Effect Transistor Volt Ohm MilliAm meter (that's what it says in the manual). Operated just like any analog VOM. Looks great, but has 10M input impedance, and that's the only difference from the "old style" VOMs. But it needs a 9V battery, it lasts almost forever though.

    -Tor
  • GenetixGenetix Posts: 1,754
    edited 2014-06-16 09:31
    Analog meters don't last as long as DMMs and quality units such as Simpson are not cheap.
    Try using Lithium 9Vs since they last a lot longer.
  • RDL2004RDL2004 Posts: 2,554
    edited 2014-06-16 09:47
    For observing a small, fluctuating or slowly changing voltage or current, an analog meter is often preferable. The constant flickering of digits and the need to manually turn off auto-ranging on a digital meter can be annoying in these situations.
  • ercoerco Posts: 20,256
    edited 2014-06-16 10:36
    Loopy Byteloose wrote: »
    It seems nobody likes the retro look and feel of an analog meter except me. Ebay has some oldies out there that look very cool and work very well.

    You're not alone, George. Despite my publicized penchant for cheap modern Ebay electronics, I have a healthy appreciation for old-school stuff, as my eclectic home furnishing collection will attest. I have a 1910 player piano, two 1920-era Victrolas, numerous vacuum tube radios & phonos from the 40's, my prize 1960 Predicta television, and scads of vacuum tube Heathkit ham gear.

    I have a georgeous vintage giant 0-36V meter at home. 8" diameter steel case, ~20 lbs, straight out of Dr. Frankenstein's lab, spade needle plus manual-set reference needle. Waiting for just the right application, likely something with cloth-insulated wire, knife switches, a Jacob's ladder and lots of Fahnestock clips. I'll owe you a photo.

    RDL is right; analog meters are far superior to digital for visualizing slow oscillations and trends.
  • GenetixGenetix Posts: 1,754
    edited 2014-06-16 11:09
    I think a scope would be useful especially if it has FFT.
  • RDL2004RDL2004 Posts: 2,554
    edited 2014-06-16 16:03
    .


    Also, let's not forget that an analog meter had a starring role (sort of) in the movie Apollo 13.

    attachment.php?attachmentid=109167&d=1402959449



    Note the other analog types on the panel behind it.



    .
    Apollo13AnalogMeter.jpg
    1024 x 575 - 260K
  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2014-06-16 19:28
    Not an LED insight!
  • Too_Many_ToolsToo_Many_Tools Posts: 765
    edited 2014-06-20 23:59
    A couple of weeks ago a friend showed me a 1910's meter based testset that he was going to sell at an upcoming swap meet...like a fool I let it walk...and it sold...going to regret that mistake.

    It just oozed quality and craftsmanship.
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