Vintage Lighting Old "Lighting Control" 2.4K dimmer voltage input

[Van]

Nothing worse than a stuffy dimmer. I think you mean SINE wave.

Sorry, I mean sine wave. I usually use french terms and I thought it means same thing.

A Sine wave flows in a Sinus rythm. One could easily check the the Sinus pattern of a Sine wave.

 

[Techniq]

If it is a standard scope - don't do it. The ground lead of the probe is earth ground. Most if not all scope probes are not cat rated. Some scopes can't handle that high of a direct voltage either - especially in x1 mode. Use a Fluke ScopeMeter of a 120 series at least. You want a floating scope that is at least cat III 300vac dated. Just my advice though. I'm just not a fan of possible arc flash. Wear safety glasses at least.

I should ask my teacher about it because last year we have checked the waveform of a standard wall outlet(120V/60Hz) with an isolation tranformer between the source and the scope.

 

[Gern]

I should ask my teacher about it because last year we have checked the waveform of a standard wall outlet(120V/60Hz) with an isolation tranformer between the source and the scope.

Please take the time to read this article from my earlier response
How safe is your voltmeter? | Brad on Broadcast

 

[DimmerDotCom]

I should ask my teacher about it because last year we have checked the waveform of a standard wall outlet(120V/60Hz) with an isolation tranformer between the source and the scope.

IF you mean you put an iso xfmr on the scope to float it then yikes!. You make a mistake like the ground lead on the hot and you floated the chassis of your lab scope to 120vac. Bad neutral - same thing even with the correct probe set up. If you have two probes of the same type, put your scope in differential mode and put one probe for hot and one for neutral, or use a differential probe. Keep that chassis grounded.

 

[derekleffew]

Re: Old "Control Lighting" 2.4K dimmer voltage input

It coulb be possibly a Electro control dimmer because there is a EC logo on the electronic board.

Electro Controls operated under the name Control Lighting in Canada. There are likely a number of people here familiar with Electro Controls dimmers who could help you if you'd post pictures of what you have.

http://www.controlbooth.com/forums/lighting-electrics/23328-electro-controls-dimmers-panel.html
The Electro Controls Archive

 

[Techniq]

IF you mean you put an iso xfmr on the scope to float it then yikes!. You make a mistake like the ground lead on the hot and you floated the chassis of your lab scope to 120vac. Bad neutral - same thing even with the correct probe set up. If you have two probes of the same type, put your scope in differential mode and put one probe for hot and one for neutral, or use a differential probe. Keep that chassis grounded.

I'm not sure about what we've done, I need to ask my teacher.

 

[Techniq]

Re: Old "Control Lighting" 2.4K dimmer voltage input

Electro Controls operated under the name Control Lighting in Canada. There are likely a number of people here familiar with Electro Controls dimmers who could help you if you'd post pictures of what you have.

http://www.controlbooth.com/forums/lighting-electrics/23328-electro-controls-dimmers-panel.html
The Electro Controls Archive

Thank you. I'll take some pics

 

[Chris15]

Geez, let's be logical about scoping mains. I severely doubt the scope was floated. I would expect the scenario was more like:
Mains -> Scope Power
Mains -> Transformer -> scope input

With the scope input on the secondary of a transformer, you've got full isolation from the mains. Probably the smart thing to do would be to use a step down transformer, say a <relevant mains flavour> to 9V AC because that will be within the native range of your scope as well...

 

[Techniq]

Please take the time to read the referenced website below at the bottom.
If you don't have the paperwork on the meter still in your possession, try looking your exact model up on-line. The info on True RMS/ not True RMS should be there. If not I'd be suspecting it is NOT True RMS. My guess is the MSRP for true RMS meters is around $100 or more, but prices may be lower. So if it was inexpensive it may not be true RMS. Make sure it is a "True RMS" rating.

My meter is a MTP 2325 and it doesn't seem to be true rms

 

[DimmerDotCom]

From Tektronix:
"“Floating” a ground referenced oscilloscope is the technique of defeating the oscilloscope’s protective grounding system – disconnecting “signal common” from earth, either by defeating the grounding system or using an isolation transformer. This allows accessible parts of the instrument such as chassis, cabinet, and connectors to assume the potential of the probe ground lead connection point. This is dangerous, not only from the standpoint of elevated voltages present on the oscilloscope (a shock hazard to the operator), but also due to cumulative stresses on the oscilloscope’s power transformer insulation. This stress may not cause immediate failure, but may lead to future dangerous failures (a shock and fire hazard), even after returning the oscilloscope to properly grounded operation! Not only is floating a ground-referenced
oscilloscope dangerous, but the measurements are often inaccurate. This results from the total capacitance of the oscilloscope chassis being directly connected to the circuit under test at the point where the common lead is connected."

That said, probably nothing will happen. But I would never do that. I was a bench tech for Tektronix for 5 years repairing oscilloscopes and consider myself well versed in their user and internal operation. My field and live voltage scopes are all Fluke ScopeMeters and for my "lab" scopes I use a Tektronix active probe isolator. And frankly, I rather use a properly rated ScopeMeter instead. Just my 2 cents and I'll be quiet now.