Powerful UVB and UVC flashlights

[Stefano]

Maybe I have to put a UVC warning here, I'm not sure.

 

Powerful (and expensive) UVB and UVC flashlights, LED-based. I have no affiliation with the seller.

https://www.engeniousdesigns.com/shop

[Stefano]

On this other website, with similar flashlights, they clearly say they get hot. They are powerful and deep UV LEDs dissipate most of the input power as heat.

[colinbm]

@Stefano The USA, Engenious Designs as a good range of UV lights. They are the same as a Dutch seller ColorGems.
I am expecting some UVC & B lights soon with this design too.
When I get them I will test them for their Spectral Irradiance in mW/cm2, & publish my results here.
I have tried to get these sellers to state the Spectral Irradiance of these lights with out any luck.
Other sellers in the USA state that their lights are Bright, Brighter & Brightest, without stating any Spectral Irradiance figures ! 
I have purchased a UVA, 365nm from an Australian seller, Fluoromins, that is the best that I have seen at 36mW/cm2 @ 380mm, which seems to be the industry standard distance to measure UV LEDs.

 

With a solid spot of 63mm on a sheet of white paper at 380mm.

[colinbm]

I need to also mention that ZWB3 only passes 40% of the UVC light at 254nm !
It is a poor choice of filter for these 254nm lights.
The Hoya 325c is a little better at passing 60% of the UVC light at 254nm.

[Stefano]

At what distance are you measuring the flashlights?

 

Also, when you specify the irradiance at 380 nm, it can't be exactly at 380 nm (monochromatic light), otherwise you would get 0. You are measuring a band of frequencies, for example those below 380 nm.

[colinbm]

@Stefano The industry standard that I have found for measuring UV LEDs is at a distance of 380mm from the emitter to the entrance pupil of the Spectral Light Meter.
That is the distance, 380mm, that I have measured both the Spectral Irradiance & the bright spot circle.

[Stefano]

I misread 380 mm as 380 nm, my bad.

 

I wonder why they use 380 mm, it's an unusual number.

[colinbm]

@Stefano It is 15 inches for the rest of he world.

[ulf]

21 minutes ago, colinbm said:

@Stefano It is 15 inches for the rest of he world.

A very small part of the rest of the world. 

https://www.statista.com/chart/18300/countries-using-the-metric-or-the-imperial-system/

After all most of us are using modern units. 

[moondigger]

Apologies for straying off topic... 

 

I understand the objective value of the metric system for measuring lengths/distances, weights, and volumes. But I've spent so long using imperial measurements that my intuition for these things was built around inches, miles, ounces, pounds, quarts, gallons, etc.

 

I can lift a container from a table and know (without thinking hard) approximately how many pounds it weighs, approximately how many inches it is along the edges, and approximately how many gallons of liquid it might hold. If somebody asked me what it weighs in kg, what it measures in cm, or how many liters it holds, I'd have to estimate in imperial units and then convert to metric.

 

Nonetheless, I regret this bias for imperial units, and wish I was brought up with the metric system so my intuition could have been built around it instead.

 

However, I fail to see any objective benefit of Celcius over Fahrenheit for temperature measurement. In fact, I think Fahrenheit is objectively superior for everyday use by human beings. For example, when considering the weather outside, it's intuitively useful to have 0 mean a very cold day, and 100 mean a very hot day. I also think it useful that degrees F are more granular/measure smaller deviations in temperature than degrees C. Some say it's useful to have 0 and 100 match the freezing and boiling points of water at sea level, but nobody has been able to explain why.

 

The metric system is objectively superior for measuring distances, volumes, and weights because it makes the math far easier. But Celcius does not do the same thing for temperatures. For example, a centimeter is ten times longer than a millimeter. But 100 degrees C is not ten times hotter than 10 degrees C. The only temperature scales that offer something close to this kind of comparative value are Kelvin and Rankine, but they're not well-suited for everyday use by humans who aren't doing advanced physics or some types of chemistry.

 

"What's the temperature outside? I'm trying to decide what to wear."

"It's 514 R."

"Oh, I'll put on a light jacket."

[Stefano]

You strongly remind me of this post: 

 

[dabateman]

To add funniness to the temperature discussion.  I was raised in Canada,  but with an American mother. So I would usually talk in Fahrenheit.  But I would get used to the cold and think that way in Celsius as reportedby the news.  

So for warm temperatures I think in Fahrenheit, everything above 50F. But for cold temperatures I think in Celsius. 

 

 

[ulf]

It is indeed difficult to relearn something you have used for a long time.

I thought it was funny that Colin said " the rest of the world". 

 

It is said that the UK is shifting over gradually to metric inch by inch. 

 

Engineering in the US sometimes use some very strange units like AWG: 

https://en.wikipedia.org/wiki/American_wire_gauge

In some old document I remember seeing an area unit as a fraction of a circular inch!

 

Sometimes sticking to archaic unit systems can be expensive:

https://www.simscale.com/blog/nasa-mars-climate-orbiter-metric/

 

Sometimes shifting to metric can can be very confusing.

In my profession, electronics design I have gotten used to the size designations of small surface mounted resistors and capacitors.

The system started based on mils and some examples are 0402, 0603, 1206.

Lately some components have gotten similar designations based on the metric system. The sizes can be like 0402, 0603, 1206 (metric) those are not physically the same sizes as the 0402, 0603, 1206. (imperial)!!! You have to check the datasheets for the dimensions to know if a 0603 is metric or Imperial.

Here I am used to the imperial type I have used for decades.

[Andy Perrin]

On 12/18/2023 at 7:28 PM, Stefano said:

You strongly remind me of this post: 

 

Oh jeez, I remember that discussion. I also really want to get back to playing with the MWIR camera — the biggest obstacle has always been the sheer weight of the camera makes it very impractical. 
 

On the units discussion, while I have a somewhat better sense of imperial units, my science education started early enough that I have a reasonably good intuition for the SI units also. I can estimate Celsius temperatures without converting, for example. (I teach thermodynamics and heat transfer, so constant conversion back and forth is a part of life for me…)

 

If speaking two languages makes one “bilingual,” does comfort with two systems of units make one “bimetric?”

[Stefano]

1 hour ago, Andy Perrin said:

If speaking two languages makes one “bilingual,” does comfort with two systems of units make one “bimetric?”

I guess so! It gives you more flexibility.

[Andrea B.]

I am completely non-bimetric. I was driving once in the Mohave Desert (on a Wildflower Safari) when Birna said "please stop a couple of meters down the road". I drove about a quarter of a mile before she finally started laughing and saying "stop! STOP!!!" 

 

Moondigger's "light jacket" comment made me laugh. The Rankine system is a complete mystery.