Page for sellers, \

[Yoshi]

Hello fellow collectors,


I know you all know how to test for continuity perfectly well, but I made a page specially designed for ebay sellers who don't know anything about electricity. You can simply send them a link to it rather than try to explain it to them every time!:
 http://bulbs.2yr.net/continuity.html


I hope I did something useful...

Regards,


-Yoshi

[Alan Franzman]

quote:Originally posted (to webpage) by Yoshi:
To test an incandescent lightbulb for continuity:
 
1.- Turn the multimeter on, and connect the pins to the multimeter if necessary
2.- Rotate the multimeter's handle to where the OHM symbol is located
3.- Notice that when you join the two pins in contact, you see that the multimeter's display changes
4.- Now place one pin on the threaded part of the base of the bulb and the other pin in the round metal plate at the bottom
5.- See if you get any numbers in the multimeter display

Yoshi, I think this webpage may be very useful.  However, I would make a few minor improvements:

I would change "pins" in step 1 to "probes" or "leads".

For step 2, you should show the ohms symbol "Ω" (html code = Ω - be sure to use a capital "O"). Also, I would change "handle" to "switch" or "control". Finally, the lowest ohms range position (usually marked "200") should be selected.

In step 3, start by noticing what the display shows when the metal probe tips are not touching anything - this is the "infinity or over-range" indication. Then notice that the display changes to zero or a very low number when the probe tips are held together.

In step 5, notice whether the display stays on the "over-range" indication, or whether it changes to zero or any number. This number is the filament resistance.

------------------
 
Alan "A.J." Franzman

Email: a.j.franzman at verizon dot net

------------------

[This message has been edited by Alan Franzman (edited February 18, 2004).]

[Yoshi]

Thanks for the suggestions!

Also thanks for the ohm symbol entity! I did try looking for it but I didn't find it. I have updated the directions using your tips, however I didn't add all of them. The 'infinity or over-range indication' is too technical a concept for people that know nothing about electricity, so it is best to omit it. (But I do understand what it means...).

Thanks again,


-Yoshi

[Alan Franzman]

quote:Originally posted by Yoshi:
The 'infinity or over-range indication' is too technical a concept for people that know nothing about electricity, so it is best to omit it. (But I do understand what it means...)

The problem here is that different meters will display different things when resistance is out of range. Does your meter really show all zeros? This seems like an uncommon indication. My meter shows a "1" on the left side of the display followed by all blanks.

Also, when you say "see if you get any numbers", this can be misinterpreted since most meters will show over range as some kind of number with a special effect, like the blanks to the right on my meter, or blinking, or something else unusual.  Since you don't know what the other person's meter will show for "infinity", I think the best thing to do is to have him put his meter in a condition which will display the over range indication, and tell him to remember what that looks like, and compare it to the display when probing the bulb.

[This message has been edited by Alan Franzman (edited February 20, 2004).]

[Yoshi]

I have an idea:

Let's just tell the sellers to see if their display "changes"; This way, no matter what the over-range indication is, the seller will only take note if it changes to something else while testing the bulb. What do you think?

I highly doubt there can be a perfect way to tell someone with absolutely no knowledge about electricity about how to test for continuity; I need to find a way that will work for most people.

Thanks  

[debook]

I doubt most people would have a multimeter, particularly if they are ignorant about electricity. My old one, died recently had no switches just lots of sockets. I just bought one on eBay that has no controls at all!! It adjusts itself to whatever it thinks it is measuring - ok for simple uses.

The simplest way to test continuity is a battery a torch bulb and a piece of wire. If the the bulb lights you have continuity - of course if it does not light you cannot be sure of the problem

[Yoshi]

quote:Originally posted by debook:
The simplest way to test continuity is a battery a torch bulb and a piece of wire. If the the bulb lights you have continuity - of course if it does not light you cannot be sure of the problem

This method won't work with carbon filament bulbs since they need a lot more than just 9 volts to even barely glow...

It's amazing that after 125 years of the invention of the lightbulb, most people don't have a clue on how they work...

[Mónico González]

Hi!
Undoubtly my favourite way to test the filament continuity, remains being the analog multimeter like the legendary ICE 680-R at Rx10 range, mainly for carbon bulbs.
The resistive range of such instruments are quite wide to detect conduction in those measuring conditions where the digital ones fails due to over or under-range, being unnecesary the continuous changing through the whole switching steps to get a coherent measuring.
Best regards,
M. Gonz?lez http://mis-bombillas.webcindario.com

[Hemingray]

Ah. that's no problem. my DMM reads 000 if i short the probes together, and "OL" for an open circuit.

... And you're done! What you actually did was test the bulb to see if electricity still passes through it. If the filament is broken, chances are it no longer has continuity. If you got nothing but zeros in the multimeter display, then your bulb probably doesn't work.

Well, actually if the meter reads all zeros, the bulb is shorted. which I dunno if that affects value in any way but i;m sure it would eat fuses left and right! Have fun and happy collecting  

[Chris Kocsis]

I agree that a multimeter is the best way to check.  You could add a sentence like, "If you aren't confident that you can do this correctly, ask a friend who is into electronics or fixing appliances to help you."

However, I would definitely clarify the part about touching the probes to the bulb contacts -- you don't want to be touching the metal part of both probes at the same time, or you will get a reading of your own resistance.  Most of us know the difference, but an inexperienced person, especially with an autoranging meter, would assume the bulb was good because the reading changed.

[Yoshi]

Thanks, I have updated the page with the new info.