Author Topic: measuring CFL voltage  (Read 3327 times)

0 Members and 1 Guest are viewing this topic.

Offline PirateguyTopic starter

  • Regular Contributor
  • *
  • Posts: 112
  • Country: nl
measuring CFL voltage
« on: September 10, 2018, 08:33:39 am »
so i took the circuit out of a cfl bulb and tried to measure the voltage it outs out
to the tube, but i can't get a steady reading on it.
all i get is either 0.5v-ish and with only 1 probe attached i get 1.5v-ish (both unstable)

so i looked around and what i read is that they usually put out around 60 volts.

i tried several of these circuits and several meters, all results are the same.
why can't i measure this?
 

Offline PirateguyTopic starter

  • Regular Contributor
  • *
  • Posts: 112
  • Country: nl
Re: measuring CFL voltage
« Reply #1 on: September 10, 2018, 08:44:57 am »
ugh, nevermind.

follwing youtube tutorials verbatim had me using the wrong pin :S
 

Offline ultrarunner2018

  • Contributor
  • Posts: 42
  • Country: us
Re: measuring CFL voltage
« Reply #2 on: September 11, 2018, 12:45:58 am »
You won't get the correct voltage unless there is a CFL bulb connected to the output. The circuits are designed specifically for that type of load, which is not constant. Also, the frequency of AC (or pulsating DC) applied to the bulb is not 60Hz. It is usually much higher.
 

Offline PirateguyTopic starter

  • Regular Contributor
  • *
  • Posts: 112
  • Country: nl
Re: measuring CFL voltage
« Reply #3 on: September 19, 2018, 11:09:39 am »
i see.
i will do some measuring with a load, thanks for the tip! :)

 

Online wraper

  • Supporter
  • ****
  • Posts: 16800
  • Country: lv
Re: measuring CFL voltage
« Reply #4 on: September 19, 2018, 11:15:12 am »
Nice way how to kill your multimeter.
 

Offline PirateguyTopic starter

  • Regular Contributor
  • *
  • Posts: 112
  • Country: nl
Re: measuring CFL voltage
« Reply #5 on: September 19, 2018, 11:40:21 am »
why would that destroy my meter?
 

Online wraper

  • Supporter
  • ****
  • Posts: 16800
  • Country: lv
Re: measuring CFL voltage
« Reply #6 on: September 19, 2018, 12:35:38 pm »
because of overvoltage.
 

Offline PirateguyTopic starter

  • Regular Contributor
  • *
  • Posts: 112
  • Country: nl
Re: measuring CFL voltage
« Reply #7 on: September 19, 2018, 12:53:31 pm »
i thought these were supposed to put out something in the 50-100v range?
 

Online wraper

  • Supporter
  • ****
  • Posts: 16800
  • Country: lv
Re: measuring CFL voltage
« Reply #8 on: September 19, 2018, 12:59:48 pm »
i thought these were supposed to put out something in the 50-100v range?
Multiply that by 10-20 times. When bulb is lit, it drops to a few hundred volts but during ignition or with open circuit, peak voltage can be huge.
 

Offline PirateguyTopic starter

  • Regular Contributor
  • *
  • Posts: 112
  • Country: nl
Re: measuring CFL voltage
« Reply #9 on: September 19, 2018, 01:52:33 pm »
could i use one of these circuits to power a small tesla coil?
 

Offline schmitt trigger

  • Super Contributor
  • ***
  • Posts: 2205
  • Country: mx
Re: measuring CFL voltage
« Reply #10 on: September 19, 2018, 01:58:12 pm »
Remeber, CFL power supplies are high frequency. Used to be 27 to 30 Khz but that caused interference with TV remotes, so the frequency nowadays is higher than 40 Khz.

I doubt that most common multimeters would be able to read the voltage at that frequency accurately.
Additionally, the voltage may have an unusual crest factor.

I would read the voltage with a scope. Use a 10X probe and start with the highest volt/div setting. As others have mentioned, the open circuit voltage is significantly higher than the operating voltage.
 

Offline PirateguyTopic starter

  • Regular Contributor
  • *
  • Posts: 112
  • Country: nl
Re: measuring CFL voltage
« Reply #11 on: September 19, 2018, 02:34:39 pm »
as luck would have it i am about to invest in my first proper scope :)

i wonder, in this context, would a plasma arc be considered a load?

and what about coils? could i wirelessly measure the frequency?
 

Online wraper

  • Supporter
  • ****
  • Posts: 16800
  • Country: lv
Re: measuring CFL voltage
« Reply #12 on: September 19, 2018, 03:06:28 pm »
I would read the voltage with a scope. Use a 10X probe and start with the highest volt/div setting. As others have mentioned, the open circuit voltage is significantly higher than the operating voltage.
:palm:  |O Are you crazy suggesting this? It's a killer for probes and oscilloscopes, way more dangerous than for multimeters. Not only scope inputs are not isolated, they and their probes usually are rated for around 300V peak only. It's not even sufficient to measure 230V RMS because peak voltage exceeds 300V. Not to say CFL ballast output where you could often see one kilovolt or sometimes even more. There are already plenty of people with destroyed oscilloscopes, probes and multimeters.
Don't ever touch CFL ballast with oscilloscope unless you have high voltage isolated probe.
« Last Edit: September 19, 2018, 03:12:27 pm by wraper »
 

Offline drussell

  • Super Contributor
  • ***
  • Posts: 1855
  • Country: ca
  • Hardcore Geek
Re: measuring CFL voltage
« Reply #13 on: September 19, 2018, 03:09:13 pm »
I would read the voltage with a scope. Use a 10X probe and start with the highest volt/div setting. As others have mentioned, the open circuit voltage is significantly higher than the operating voltage.

Ummmm, i don't think probing a couple thousand volts with a X10 oscilloscope probe is a very good idea.   :palm:

Edit:  Like wraper said, in the post above...
 

Offline PirateguyTopic starter

  • Regular Contributor
  • *
  • Posts: 112
  • Country: nl
Re: measuring CFL voltage
« Reply #14 on: September 19, 2018, 03:24:25 pm »
would a diy high voltage probe work?
(the ones where u multiply the internal resistance of the meter)
 

Offline schmitt trigger

  • Super Contributor
  • ***
  • Posts: 2205
  • Country: mx
Re: measuring CFL voltage
« Reply #15 on: September 19, 2018, 04:02:21 pm »
Guys, guys ,guys.

Take a deep breath and slow down.

I actually worked for several years for an electronic ballast manufacturer.  Universal Lightning Technologies, if you ask. I KNOW WHAT I AM TALKING ABOUT.
Very high startup voltages are only found in instant start ballasts. For a long, 75 watt, 8 feet tube, the starting voltage was at its highest 800 volts.

For preheat tubes, and specifically, for short length tubes, the startup voltage is far lower.

For a preheat, 4 feet, T12 tube the open circuit voltage was around 250 volts.

We were in the process of starting to build CFLs when I left the company so I did not have much experience with them, but they were always preheat. I have opened up many CFLs during these last years, and with the exception of some piss-poor Chinese ones, all the CFLs I have seen are not instant start but preheat ones.

What you are correct though, is that you have to use good probes which are rated for the correct voltage.
« Last Edit: September 19, 2018, 04:14:06 pm by schmitt trigger »
 
The following users thanked this post: SeanB, edavid

Offline schmitt trigger

  • Super Contributor
  • ***
  • Posts: 2205
  • Country: mx
Re: measuring CFL voltage
« Reply #16 on: September 19, 2018, 04:13:30 pm »
I found this information, for an instant start ballast. Please note these are 72 inch and 96 inch tubes. Long, long tubes.

 

Offline Gyro

  • Super Contributor
  • ***
  • Posts: 9410
  • Country: gb
Re: measuring CFL voltage
« Reply #17 on: September 19, 2018, 05:40:34 pm »
The great Jim Williams was a master of these sort of measurements. Go and look at LT AN65 and scroll to Appendix C.

http://www.analog.com/media/en/technical-documentation/application-notes/an65fa.pdf

Listen to the master:
Quote
Figure C10 lists some recommended probes along with their characteristics. As stated in the text, almost all standard oscilloscope probes will fail3 if used for this measurement.

Note 3: That’s twice we’ve warned you nicely.

 ;)
« Last Edit: September 19, 2018, 05:54:12 pm by Gyro »
Best Regards, Chris
 

Offline edavid

  • Super Contributor
  • ***
  • Posts: 3381
  • Country: us
Re: measuring CFL voltage
« Reply #18 on: September 19, 2018, 06:47:01 pm »
The great Jim Williams was a master of these sort of measurements. Go and look at LT AN65 and scroll to Appendix C.

http://www.analog.com/media/en/technical-documentation/application-notes/an65fa.pdf

Listen to the master:
Quote
Figure C10 lists some recommended probes along with their characteristics. As stated in the text, almost all standard oscilloscope probes will fail3 if used for this measurement.

Note 3: That’s twice we’ve warned you nicely.

CCFL backlight tubes and inverters are very different from CFL light bulbs.  This app note and warnings are not relevant to OP's question.
 

Online wraper

  • Supporter
  • ****
  • Posts: 16800
  • Country: lv
Re: measuring CFL voltage
« Reply #19 on: September 19, 2018, 06:47:48 pm »
I found this information, for an instant start ballast. Please note these are 72 inch and 96 inch tubes. Long, long tubes.
This is not maximum that can be there and especially with bulb removed or damaged.
Quote
What you are correct though, is that you have to use good probes which are rated for the correct voltage.
Something you did not mention. Therefore I criticized your suggestion. Don't forget this is a Beginner thread and op had no clue about voltages.
 

Offline Gyro

  • Super Contributor
  • ***
  • Posts: 9410
  • Country: gb
Re: measuring CFL voltage
« Reply #20 on: September 19, 2018, 06:52:16 pm »
CCFL backlight tubes and inverters are very different from CFL light bulbs.  This app note and warnings are not relevant to OP's question.

Doh, I misread and missed the absence of the extra 'C'.
« Last Edit: September 19, 2018, 06:56:44 pm by Gyro »
Best Regards, Chris
 

Online wraper

  • Supporter
  • ****
  • Posts: 16800
  • Country: lv
Re: measuring CFL voltage
« Reply #21 on: September 19, 2018, 06:59:07 pm »
CCFL backlight tubes and inverters are very different from CFL light bulbs.  This app note and warnings are not relevant to OP's question.
If you read it, that app note does mention hot cathode fluorescent lamps. Also as I previously said when there is no lamp or lamp is damaged, peak voltage can go up a lot.
« Last Edit: September 19, 2018, 07:01:17 pm by wraper »
 

Offline PirateguyTopic starter

  • Regular Contributor
  • *
  • Posts: 112
  • Country: nl
Re: measuring CFL voltage
« Reply #22 on: September 19, 2018, 08:49:54 pm »
speaking of beginner threads, i would really appreciate it if you guys could stop comparing penis size for 2 seconds
and maybe answer 1 or 2 of my questions?

Quote
could i use one of these circuits to power a small tesla coil?

Quote
i wonder, in this context, would a plasma arc be considered a load?

Quote
and what about coils? could i wirelessly measure the frequency?
Quote
would a diy high voltage probe work?
(the ones where u multiply the internal resistance of the meter)

 

Offline TheNewLab

  • Frequent Contributor
  • **
  • Posts: 290
  • Country: us
Re: measuring CFL voltage
« Reply #23 on: September 20, 2018, 05:59:07 am »
interesting.
1.) regarding a tesla coil, I would look at info on DIYing a tesla coil first. I suspect Tesla coils use much higher frequency.
2.) I know nothing about plasma arc..duck duck DIY plasma arc? or DIY plasma arc? or what's the frequency of plasma arc?
3.)  coils, like clamp meters and hall effect are designed for measuring high currents - I would look into TV repair methods that have KV levels of voltage.
4.)  DIY HV probes are a mixed bag. I am sure plenty of people. likely much more experienced than I would say nothing except a quality built HV prove. However, I have seen instructions on how to make two types of DIY HV probes from Delton Horn repair book How to Repair Almost Anything
It's old..Homer Davidson was big on HV probes for TV repair too.
For me...it is all about keeping a distance...say 3 or 4 foot long pole on the probe, in case the DIY probe flashes over. 

Please, note that I am a hobbyist, not a pro.. I am sharing how I would approach it...listen to anyone more knowledgeable than me FIRST!.
Thanks for posting this question
 

Offline PirateguyTopic starter

  • Regular Contributor
  • *
  • Posts: 112
  • Country: nl
Re: measuring CFL voltage
« Reply #24 on: September 20, 2018, 07:35:35 am »
thanks for the reply :)

1: i did look around and played with this java calculator. turns out small coils like the one i had in mind 300-600 turns
will run at hundreds of khz, but a larger size coil with more windings will resonated at a lower frequency.
2: with plasma arc i just mean the spark u can make with high voltage. like a jacob's ladder, would that act as a load and
make the voltage drop?
3: i was thinking only of measuring frequency this way. if i just rig up 2 coils, one to transmit and one as an antenna, i'd imagine
i can get some sort of signal, and the frequency at least should not be effected by reception quality.
4: well i suppose i can just test it out with a cheap meter. i wasn't planning on measuring high current anyway.
based on some tutorial videos i watched, i measured the internal resistance of several meters and all are 1 meg and
so a 99meg resistor array should give me a 100x factor. should be enough for the cfl circuit, but i suppose i could rig up a spark gap
for extra safety.
 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf