Conventional Fixtures Test what lamp installed without removing cap

[iLightTheStage]

So, I want to pick all of your brains because I can't think of a way to do this but I feel like it's possible:
How could I build a tool to test which wattage (375w/575w/750w) lamp is inside a source4 without removing the cap?

I'd like to go with the simplest solution, and avoiding advanced electronics such as ICs and such. We currently open caps on large pulls to make sure the lamps are set correctly for the gig (some of our guys are lazy and don't label the fixture when they change the lamp from the 575w we default to). But it would be much nicer to be able to plug in the fixture to determine that the lamp is good AND the right wattage. [sidenote: I much prefer testing the lamp by plugging it in, because continuity will never tell you that the lamp was about to blow.]

 

[tyler.martin]

Just use a DMM and measure the resistance. I can't remember the numbers off the top of my head, but there's a difference in all wattages

 

[derekleffew]

One time my amprobe proved invaluable: I had a 50gallon trash can full of unlabeled PAR64 lamps, a mixture of 500W and 1000W. The manufacturers' printing was either faded or worn off. I did as STEVETERRY suggested and made an Edison to 2P&G adapter, using the Blk,Wht,Grn inner wires from a 2' piece of 12/3 SOOW. Clamped around the hot or neutral wire, when the meter read 8.3A or so, I knew I had a 1000W; when it was just was over 4.0, I knew I had a 500W. I could ascertain by looking whether it was WFL, MFL, or NSP. After testing each lamp, I wrote "1K MFL" or "500 NSP" or whatever on the ceramic with black Sharpie™. Since then I've always written on the ceramic as soon as I open a new PAR64 lamp box.

Today, knowing that such a product is readily available, I'd use the following along with the appropriate adapters and clamp meter:

480172 - AC Line Splitter

One could probably build something cleaner and more compact, but it would cost more. Panel mount ammeter s are not inexpensive.

EDIT: Oh! Oh! Mr. Kotter! Mr. Kotter! Here's your answer; forgot about this:

P3 - Kill A Watt
P3 International Kill-A-Watt Electricity Usage Monitor: iPods & MP3 Players : Walmart.com

EDIT2: Hmm, maybe not accurate enough? I just got a reading of 515W for an EHD, 586W for a GLA, and 730W for an EHG. Perhaps one should plan on powering the Kill-A-Watt (someone here recently had a similar device but I can't remember the name) via a Variac to insure a steady 120 or 115V voltage supply. Then again, should be close enough to tell the difference between 375, 575, and 750W. But 115/120V lamps will throw it a curveball.

 

[Les]

Hmm, maybe not accurate enough? I just got a reading of 515W for an EHD, 586W for a GLA, and 730W for an EHG.

I wouldn't be surprised if those readings are accurate. Like the beam angle designations on lens tubes ;p.

 

[iLightTheStage]

Today, knowing that such a product is readily available, I'd use the following along with the appropriate adapters and clamp meter:

480172 - AC Line Splitter

One could probably build something cleaner and more compact, but it would cost more. Panel mount ammeter s are not inexpensive.

EDIT: Oh! Oh! Mr. Kotter! Mr. Kotter! Here's your answer; forgot about this:

P3 - Kill A Watt
P3 International Kill-A-Watt Electricity Usage Monitor: iPods & MP3 Players : Walmart.com

EDIT2: Hmm, maybe not accurate enough? I just got a reading of 515W for an EHD, 586W for a GLA, and 730W for an EHG. Perhaps one should plan on powering the Kill-A-Watt (someone here recently had a similar device but I can't remember the name) via a Variac to insure a steady 120 or 115V voltage supply. Then again, should be close enough to tell the difference between 375, 575, and 750W. But 115/120V lamps will throw it a curveball.

I never thought about using the kill-a-watt. I like it. Cheap, easy solution. Using an ammeter would've been more than I'd be willing to spend, and not nearly as clean.

 

[silicsound]

You could use a multimeter to measure the resistance, the higher the resistance lower the wattage. If you try and use ohms law to find the resistance of each lamp wattage, you will find that the resistance will be around 20 times less in practice since the lamp is cold. As far as the condition goes, resistance should increase with age.

You could also just set up a source four that you know has a 575w lamp in it and aim it at the cyc, and compare the brightness of the unknown units to it. As far as the condition goes you could use a piece of welder's glass(make sure its #14 and has a gold coating if its a polycarbonate filter, two pieces of #7 does not equal #14). I use them to check the reflector by looking in to the barrel while the unit is on, you might be able to determine the condition of the lamp that way.

 

[soundlight]

We used a Kill-A-Watt at a shop I worked at for a summer a couple years ago. Was plenty accurate enough to determine between 575 and 750 lamps. We had 2 built in to boxes opposite each other at the conventionals shop bench so that 2 people could test lights at the same time. The boxes were attached to the shop bench and had the units mounted to them and if I remember right also had stagepin plugs on them. Kinda hacked the kill-a-watt to suit the purpose.