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$5 AC Ammeter Sale? — Parallax Forums

$5 AC Ammeter Sale?

ercoerco Posts: 20,256
in General Discussion
This seller has a "$5 off" sale on certain items now. Seems too good to be true, but if course I ordered. Seller might come to his senses and stop the sale and/or cancel orders, but pounce if you're a gamblin' man! Add to cart to see discount. I'll bet they meant 5% off, not $5...

$5 clamp-on AC ammeter (US shipper!): https://www.ebay.com/itm/Digital-LED-Clamp-Meter-Tester-AC-Volt-Amp-Multimeter-Current-Resistance-Tester/164248259970

$2 2" LCD SPI display: https://www.ebay.com/itm/2-2inch-240x320-TFT-LCD-DisplaySPI-ILI9341-for-51-AVR-STM32-ARM-PICArduino/164252531768

Also check the "see other $5 off items" link on those pages.

Comments

  • PublisonPublison Posts: 12,366
    I get the $5.00 off when I go to checkout. Get it while you can!
  • pmrobertpmrobert Posts: 673
    Yes! Bought two more for backup amp-clamp meters for a couple of coworkers.
  • ercoerco Posts: 20,256
    OMG, now they are just $2! $7 price -$5 discount: https://www.ebay.com/itm/Digital-LED-Clamp-Meter-Tester-AC-Volt-Amp-Multimeter-Current-Resistance-Tester/164248259970

    I already received the two I ordered for $5, so it's not a scam!
  • ercoerco Posts: 20,256
    And if you want 1280 resistors for $7: ($12-$5 discount)

    https://www.ebay.com/itm/1280Pcs-Metal-Film-Resistor-1R-10M-64-Models-Resistors-Assortment-Kit-Durable/164212130241
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    I ordered one but did not get the $5.00 discount. Still, at $7, it's a bargain!

    -Phil
  • PublisonPublison Posts: 12,366
    Just got one for 2 bucks! How can they do that with USA shipping?!
  • pmrobertpmrobert Posts: 673
    One thing to watch out for is that they won't do 480 VAC. This very likely matters to no one but me but wanted to mention that. They max out at 450 VAC. They are still a very nice deal for intended use for < 450 VAC.
  • R BaggettR Baggett Posts: 155
    Great for low voltage work on the bench, but PLEASE don't try to use this on anything where arc flash is a concern, power distribution systems, etc, even at 240V. Non category rated instruments like these can make a heck of a bang if anything goes wrong! in your hand!!! as in on-fire live fragments in your hand!!!!!

    (Don't ask how I know this....)
  • kwinnkwinn Posts: 8,697
    R Baggett wrote: »
    Great for low voltage work on the bench, but PLEASE don't try to use this on anything where arc flash is a concern, power distribution systems, etc, even at 240V. Non category rated instruments like these can make a heck of a bang if anything goes wrong! in your hand!!! as in on-fire live fragments in your hand!!!!!

    (Don't ask how I know this....)

    High currents and voltages definitely call for using a clamp on ammeter and great care.
  • ercoerco Posts: 20,256
    I never used a clamp-on AC ammeter before. Tried to measure the 240V current charging my EV but got zero. Thought mine was defective, so I RTFM and discovered that it must clamp around ONE conductor only. Shocking!
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    Yup. That's why these things exist:

    https://www.grainger.com/product/3ZH94

    -Phil
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    BTW, clamping around both wires isn't entirely useless. If you see any current at all, it's the sign of a ground fault.

    -Phil
  • pmrobertpmrobert Posts: 673
    Phil Pilgrim (PhiPi) wrote: »
    BTW, clamping around both wires isn't entirely useless. If you see any current at all, it's the sign of a ground fault.

    -Phil

    Yes! Very important factoid. I use this technique 5 days a week on some high power machines. Sometimes a surprise awaits you.
  • Duane DegnDuane Degn Posts: 10,588
    pmrobert wrote: »
    Yes! Very important factoid. I use this technique 5 days a week on some high power machines. Sometimes a surprise awaits you.

    Am I correct to assume these machines don't have a third ground wire?

    A fault which sends the current back down the ground wire wouldn't show up using this technique, right?

  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    Duane Degn wrote:
    A fault which sends the current back down the ground wire wouldn't show up using this technique, right?
    True, but the fault might be to a more local earth ground, which would not return via the ground wire.

    -Phil
  • pmrobertpmrobert Posts: 673
    edited 2020-10-21 23:48
    I was referring to three phase motors. They do have a ground and a slight fault in any of the phase windings (to ground) does show in the ground wire and a current imbalance between phases. A megger typically identifies the culprit. It's usually an indication of deteriorating insulation and they'll run for a while before they don't. Phase-to-phase faults are quite different and generally shows themselve in a short, spectacular and smoky event. Of course, here in S FL, US, our local utility is very fond of using an open delta scheme which throws all this out the window.
  • sam_sam_samsam_sam_sam Posts: 2,286
    That depends on how degrading of the winding are on a motor when using a merger I have seen where it would just be barely in the green zone and the motor would have issues any way

    But generally speaking you are right that a merger would tell if you have an issue to ground but not between windings
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