ProSoundWeb Community

Please login or register.

Login with username, password and session length
Advanced search  

Pages: 1 [2] 3   Go Down

Author Topic: Meter and test every show  (Read 9160 times)

Jared Bartimus

  • Jr. Member
  • **
  • Offline Offline
  • Posts: 50
  • Normal, IL
Re: Meter and test every show
« Reply #10 on: October 14, 2013, 04:21:40 pm »

Metering power before plugging in is like checking the fuel quantity on an airplane before departure. Just do it, even if you "know" it's OK.

I have an observation on using a regular volt meter, as opposed to a non-contact "AC voltage checker", for verifying that grounds are not hot. I do not suggest that anyone do this as a matter of course, as it's a little non-standard and potentially hazardous, and put it out here for the amusement of folks who have more of an experimental mind set when it comes to electricity.

Get up on your rubber soles and grab one probe of the meter. You have now become a capacitively-coupled ground reference to the universe (or at least your immediate vicinity). The other probe can now be used to check that equipment grounding conductors and grounded circuit conductors are grounded, and that hots are hot. If your meter is healthy you're connecting yourself to the line through a 10 M Ohm resister, so you won't die, even if you're grounded. (Hell, you won't even trip the GFI.) The reason for getting up on your soles is in case the meter is internally shorted or you plugged the leads into the current hole by mistake.

Actually, you could make up a special lead with a, say, 10 M Ohm, high-voltage resistor in series. With triple redundancy (meter, external resistor, and dry rubber soles) this would be pretty safe.

Like I said, only by qualified personnel, laboratory use only, etc.

--Frank

I don't know about other digital meters but mine (extech ex330) shows 10-20V if you just touch one probe to 120V, the other can be completely disconnected.  The meter has a non contact voltage detector built in but it isn't sensitive enough to pick up which is hot.  I wouldn't want to rely on it 100% but it is safer than using your body as a ground.
Logged

Kemper Watson

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 420
Re: Meter and test every show
« Reply #11 on: October 14, 2013, 04:28:45 pm »

It was the owner of the generator, not "some guy that brought the genny" He went through all the BRAND NEW cables he bought and straightened  the problem out.

Edit: He bought the cables from a new distributor somewhere on line. I had never had a problem with his distro's ever, in 6-7 years of working with him ..Stand up guy. He will never NOT check brand new cables again..

I don't know why this posted like this.. Delete if necessary
« Last Edit: October 14, 2013, 06:22:00 pm by Kemper Watson »
Logged

John Roberts {JR}

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 16115
  • Hickory, Mississippi, USA
    • Resotune
Re: Meter and test every show
« Reply #12 on: October 14, 2013, 04:35:17 pm »

I don't know about other digital meters but mine (extech ex330) shows 10-20V if you just touch one probe to 120V, the other can be completely disconnected.  The meter has a non contact voltage detector built in but it isn't sensitive enough to pick up which is hot.  I wouldn't want to rely on it 100% but it is safer than using your body as a ground.
Again not really encouraging off-sheet use of test equipment, my cheap rat-shack digital VOM measures 10-15VAC on hot, and around 2.5VAC on neutral, with only one lead touching anything.

Just to be safe remove the other meter lead completely when ignoring our earlier advice to not do this.  ;D

JR

Logged
On the internet people tell you everything "they" know, not the answer to "your" question.....  http://circularscience.com/

Mike Sokol

  • Moderator
  • Hero Member
  • *****
  • Offline Offline
  • Posts: 3228
  • Lead instructor for the No~Shock~Zone
    • No~Shock~Zone Electrical Safety
Re: Meter and test every show
« Reply #13 on: October 14, 2013, 05:29:12 pm »

Mike, how about a little detour (new topic) on arc flash and PPE?
Good idea. I'm hanging out in Austin Texas teaching seminars for a few days (and supposed to be grading mid-term exams) so it will probably be next week before I have some free time.

Certainly as we work with ever higher amperage distro prower, an arc flash can be even more dangerous than being shocked by 120-volts. The reason is, you can probably have your heart restarted if you're "just" shocked, but if you're up close to an arc flash without your PPE (Personal Protection Equipment), you will probably require skin grafts and rehabilitation if you even survive the explosion of superheated copper plasma coming at you faster than the speed of sound.

That's why you shouldn't work in live electrical panels if you can avoid it. And going into a hot panel "bare back" without proper training and protective gear is an invitation to becoming a very bad looking corpse. I have lots of pictures I'll share next week on a new thread.   
Logged
Mike Sokol
mike@noshockzone.org
www.NoShockZone.org

Mac Kerr

  • Old enough to know better
  • Administrator
  • Hero Member
  • *****
  • Offline Offline
  • Posts: 6240
  • Audio Plumber
Re: Meter and test every show
« Reply #14 on: October 14, 2013, 05:48:03 pm »

Good idea. I'm hanging out in Austin Texas teaching seminars for a few days (and supposed to be grading mid-term exams) so it will probably be next week before I have some free time.

I guess you're not going to any music festivals. ACL looks pretty wet.

Mac
Logged

Mike Sokol

  • Moderator
  • Hero Member
  • *****
  • Offline Offline
  • Posts: 3228
  • Lead instructor for the No~Shock~Zone
    • No~Shock~Zone Electrical Safety
Re: Meter and test every show
« Reply #15 on: October 14, 2013, 06:35:37 pm »

I guess you're not going to any music festivals. ACL looks pretty wet.

Mac
Austin had 12 inches of rain here in the last 48 hours. Yikes!!!
Logged
Mike Sokol
mike@noshockzone.org
www.NoShockZone.org

Ryan C. Davis

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 254
  • SL,UT
Re: Meter and test every show
« Reply #16 on: October 14, 2013, 10:57:55 pm »

Austin had 12 inches of rain here in the last 48 hours. Yikes!!!

Yep, massive amounts of rain. BUT according to Bob L, new england can just "soak up" 12" of rain. Too bad ACL isn't in Boston.
Logged
Ryan Davis

Jared Bartimus

  • Jr. Member
  • **
  • Offline Offline
  • Posts: 50
  • Normal, IL
Re: Meter and test every show
« Reply #17 on: October 14, 2013, 11:25:59 pm »

Again not really encouraging off-sheet use of test equipment, my cheap rat-shack digital VOM measures 10-15VAC on hot, and around 2.5VAC on neutral, with only one lead touching anything.

Just to be safe remove the other meter lead completely when ignoring our earlier advice to not do this.  ;D

JR

I would never recommend doing it as a primary method but if you don't have a non contact meter (get one) and only attach one lead it shouldn't add any other danger.  It is usually something I just notice when checking voltages normally.  If when I make the first connection with a probe it doesn't spike correctly I get suspicious.
Logged

Jonathan Johnson

  • Hero Member
  • *****
  • Online Online
  • Posts: 2908
  • Southwest Washington (state, not DC)
Re: Meter and test every show
« Reply #18 on: October 15, 2013, 11:49:31 am »

It is usually something I just notice when checking voltages normally.  If when I make the first connection with a probe it doesn't spike correctly I get suspicious.

Ah, yes. It's important to be familiar with your equipment and its normal behavior. It's always a good idea to test your test equipment against known conditions before testing unknown conditions -- every time you pull it out of the toolbox.

If you didn't successfully test your meter against a working source of known voltage, don't trust it when it says 0V. A broken lead can kill you.
« Last Edit: October 15, 2013, 11:51:57 am by Jonathan Johnson »
Logged
Stop confusing the issue with facts and logic!

John Roberts {JR}

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 16115
  • Hickory, Mississippi, USA
    • Resotune
Re: Meter and test every show
« Reply #19 on: October 15, 2013, 12:39:36 pm »

While this is somewhat related, we need to careful even when metering an outlet for voltage. If the VOM is in some other range than AC voltage, it is possible that the meter with one lead plugged into hot could pass lethal current to the other lead.

Good practice would be to plug into the ground or neutral first, and not touch metal on any loose lead ever.

JR

PS: I am not aware of anyone getting hurt this way, but it could happen so is worth mentioning.
Logged
On the internet people tell you everything "they" know, not the answer to "your" question.....  http://circularscience.com/
Pages: 1 [2] 3   Go Up
 


Page created in 0.102 seconds with 24 queries.