Turn It Up To 11 – How To FAKE a Light Test


The Truth About DE HPS PAR Testing.

Asking how much power a 1000w system puts out should be like asking who’s buried in Grant’s tomb, but it’s not. Ballast makers play games with output power like VW hacking Diesel exhaust, which is why a light meter can be a grower’s number one source of fake news.

[quote]Turning it up to 11 takes more power, costs more cash, shortens equipment life, and makes a not-so-great ballast look a lot better than it is.[/quote]

Above: How much will a PAR meter really tell you about your Grow Lights performance?


Here’s how you get the real scoop:


A PAR meter measures light which is a good place to start for DE HPS PAR testing, but by itself it’s not enough. In a typical YouTube ballast test with a yardstick and a PAR meter, and Measuring in uMole/s, for example, who wins this DE HPS PAR test shootout?

Your PAR meter ranks them, but it really looks at this:

 Correct PAR output by dividing by output power, and you see what happens to the results in this DE HPS PAR test:


Comparing a 1000w ballast to one on Silent Boost gives you the wrong answer. One well-known maker ships at 1045w, another at 1065w, and one truly unscrupulous builder clocks in close to 1080w because they know PAR meters sell lights. There’s even one brand that puts out less power to make their more expensive lights look better because if a PAR meter is what you’ve got, than that’s the needle they’re got to move. So they turn up it to 11.

Turning it up to 11 takes more power, costs more cash, shortens equipment life, and makes a not-so-great ballast look a lot better than it is. The net is you end up with something that measured well, but doesn’t perform well.

Above: Proper HID Output Testing Equipment

To measure output power, use an oscilloscope with a differential probe and a clip on current probe and set the ‘scope to show you the Volts x Amps, or use a ballast tester like this one from Everfine. Doing good lab work takes good lab equipment, and labs like UL, CSA, Intertek and TUV have the equipment to do it right. If the report came from a Nationally Recognized Testing Laboratory, you’re dealing with a certified lab whose results you can trust. A guy with a PAR meter on YouTube, maybe not so much.

Happy growing!

Greg Richter is Managing Director of Revolution Microelectronics in Bangkok and the engineer behind the DEva low frequency square wave grow light. He can be reached at

Is This YOUR Lighting Supplier?! (See BELOW). Nigel Tufnel of Spinal Tap explains the benefits of cranking  it up to “Eleven”:

[youtube width=”560″ height=”315″ video_id=”KOO5S4vxi0o”]


Be the first to comment

Leave a Reply

Your email address will not be published.