Continuation of work done last year, described in this article.
Here at georgesworkshop.ca I have eight dual four foot ceiling mounted fluorescent fixtures. I want to add more light in the center of the main shop, probably two more fixtures, so ten altogether. The purpose of this work is to compare a variety of alternatives to come up with safe, modern high efficiency shop lighting while re-using as much as possible from the existing fixtures.
Because I wanted to do a series of comparisons, and it is not very convenient with the fixtures mounted on the ceiling, I built a simple test jig from wood scraps to temporarily hold a fixture to be tested at a standard height above a table (about 38").
The feet of the jig also can support a fixture off the table when I want to remove the cover to attach a thermocouple to the ballast or other changes. Some of these fixtures have sharp edges and protruding screws out of the backside that might scratch or damage the table surface. The two shelf brackets support the fixture when it is in the raised position yet allow easy changeover between fixtures and access to the bulbs.
A light meter will be positioned on the table surface directly below the center of the fixture.
I used a number of instruments to measure the energy into the lamps and the light output. None of these tools are particularly special or expensive. Since I would be making a series of comparisons, the absolute accuracy was not as important as consistent results and I would achieve those results by making careful measurements in the same way (as much as possible) between the various alternatives.
footcandles and I used it on the most sensitive scale (200 footcandles full scale). I have just looked at "light meters" on Ebay and meters of this style and class sell for about CAD$25-50. Mine gives stable and consistent results and for my purposes, to know whether one source is relatively bighter than another, the absolute accuracy is not that important.
One footcandle is equal to one lumen per square foot or approximately 10.764 lux.
To help get consistent results, 1) I started the tests with a fresh 9 volt battery, 2) I placed a masking tape cross-hair on the table top so I put the meter head in the same place each time if I had to move it and 3) I tested the light meter before each fixture under an LED table lamp nearby (not shown) in the same position under the same bulb and ensured that I got the same reading each time before beginning the test run.
"Kill A Watt" meter from P3. I have an older version that I have used for a number of years. The current model of what I have is a P4400 but mine seems to be the same.
The Kill A Watt plugs into a power outlet (in this case a Woods extension cord) and itself has a socket on the front into which I plug the cord to the fixture I am testing. The Kill A Watt makes its measurements on the electricity which passes through it to the load, the fixture I want to test.
I use the Kill A Watt to read the voltage, the current (in Amps), the Power (in watts) and the apparent power (in VA). The built in timer is also handy for telling how long the test lamp has been ON. I make a series of measurements at 5, 10, 15, 20, 25 and 60 minutes and after each measurement, I set the Kill A Watt to show elapsed time to help prompt me for the next measurement.
The Fluke 52II uses two thermocouples to sense temperature. One of the thermocouples is shown in the picture, the small bead at the end of the wire. One thermocouple was loosely attached to a wood beam across the top of the test jig about the same height as the fixture, but not touching it, just hanging in the air. The other sensor I used to measure the temperature of the ballast in the fixture.
The Woods extension cord which the Kill A Watt is plugged into is itself plugged into the auto transformer. The auto transformer is plugged into a regular grounded wall outlet in the shop.
I have one more objective that I have not fully figured out yet. I want some measure of the color temperature or spectra of the lamps. By now we are probably all familiar with the desirability of "warm white" light as opposed to "cool white". Without an expensive spectrophotometer, such as one of these, I must improvise.
If you have any ideas about how to do this, please leave me a comment below (I moderate the comments to prevent spam so they appear after I approve them) or write to me directly at george at ffwdm dot com.
Thanks for your interest!
Lion's Head, Ontario, Canada
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