USB Portable Powerful 12W Custom LPM

[Jstr]

Looks great, put me down for one please

 

[Podo]

It's a really great LPM if you don't need data logging and want a quick and precise readings for your handheld lasers! Feel no hesitate pm me at anytime!

 

[rhd]

It's a really great LPM if you don't need data logging and want a quick and precise readings for your handheld lasers! Feel no hesitate pm me at anytime!

It's USB.... how does it not have data logging? Isn't that just a matter of the software running on the PC, not the LPM hardware?

Can you show a photo of the software?

 

[Podo]

The usb plug is a more convenient way as a power connection to the led display and the display is not configured with RS232 output right now though the point is the sensor don't require any power. One can connect it to any display devices which have more functions.

 

[rhd]

The usb plug is a more convenient way as a power connection to the led display and the display is not configured with RS232 output right now though this point is the sensor don't require any power. One can connect it to any display devices which have more functions.

Wait, so this doesn't even interface with a PC? It's just the TEC, a heatsink, and an LED voltmeter, for $150?

 

[Podo]

Really? Even before I lowered my first suggested price, that wasn't high as $150 neither.

 

[Jstr]

Re: USB Portable Powerful 12W Custom LPM "Persale Price"

Wait, so this doesn't even interface with a PC? It's just the TEC, a heatsink, and an LED voltmeter, for $150?

try $85. A great deal for a 10 watt LPM with very good response time for being thermal, no matter how you look at it.

 

[rhd]

try $85. A great deal for a 10 watt LPM with very good response time for being thermal, no matter how you look at it.

$85 is a lot better than the original $150. I'm glad the price criticism of that original selling price was taken on board.

While I still struggle to understand what you're paying for here if the USB is fake, and this doesn't actually contain any "brains" to interface with a PC, I suppose there are worse ways to spend $85.

It still seems to me that this is just the $50 DIY LPM that has been kicking around for a while on LPF (http://laserpointerforums.com/f42/diy-thermal-lpm-under-50-a-51129.html). And while I have a bit more faith in the design of the BlueFan Basic (http://store.bluefan.nl/index.php?location=power_meters), particularly the larger heatsink, admittedly, at 70 euros, it's not that much cheaper than the above, and I'm not sure if it's still available.

I still can't get past this 12W claim though. How is that tiny heatsink dissipating sufficient heat that the differential (which is all it can measure) doesn't shrink dramatically and hugely impact readings? I mean, just hop on Digikey and check out the specs of heatsinks of that size and style. You're not going to find one that can handle 12W without a significant rise in temperature. Good design and smart electronics only take you so far, it's pretty hard to get around the reality of heat...

 

[Podo]

Re: USB Portable Powerful 12W Custom LPM "Persale Price"

The tec is only about 1.6mm thick under covered a graphite coated copper sheet with 15*15 active surface. A normal tec is about 3mm and if you still think this is a $50 lpm that people are doing a long time ago.

At least that explained all your skeptical theories. It can handle the heat because it is a total different tec being used with 50*50*40 heatsink together, I will try to not dig deep down on this as I am not the creator.

Most of the cost is from the sensor itself but not a an interface or programme for computer output as it can be done quite easily and cheap.

And if you still feeling struggle to believe what he accomplished here is not a replica from old tutorials that some members posted years ago, how about a question for you?

Can you explain how to achevie 1mV=10mW sensor without any power feeding?

 

[rhd]

And if you still feeling struggle to believe what he accomplished here is not a replica from old tutorials that some members posted years ago, how about a question for you?

Can you explain how to achevie 1mV=10mW sensor without any power feeding?

Don't go ad hominem just to avoid the (inconvenient) skepticism about the ability of that tiny heatsink to absorb 12W without a substantial rise in case temperature. In any event, I'm not taking issue with the fact that your LPM needs a power feed, I believe most do. I'm taking issue with the unit's inexplicable ability to avoid the basic thermal dissipation specs of its heatsink, and now, with your use of logically fallacious discussion strategies in responding to criticism.

 

[Jstr]

Re: USB Portable Powerful 12W Custom LPM "Persale Price"

Don't go ad hominem just to avoid the (inconvenient) skepticism about the ability of that tiny heatsink to absorb 12W without a substantial rise in case temperature. In any event, I'm not taking issue with the fact that your LPM needs a power feed, I believe most do. I'm taking issue with the unit's inexplicable ability to avoid the basic thermal dissipation specs of its heatsink, and now, with your use of logically fallacious discussion strategies in responding to criticism.

I can see your concern for heating, and I was thinking the same thing, so I did some calculations:

So let's say the LPM absorbs 180 joules of heat from a 12 watt laser over 15 seconds response time. The specific heat of aluminum is .9 J/gram Kelvin and I'd estimate that heatsink to be about 100 grams, so we have 180J=(.9)(100)(delta temp). The rise in temperature should be 2 degrees Celsius and that does not account for dissipation from the heatsink over 15 seconds or the heat that goes into electrical energy. Not to mention that who is going to have a 12 watt laser?? (And where can I buy one?! ) I could be wrong, but I bet <2 degrees can't skew the reading too terribly.

Maybe we can get a better heatsink, but I'm not all that concerned because my most powerful laser is around 3 watts

 

[rhd]

I can see your concern for heating, and I was thinking the same thing, so I did some calculations:

So let's say the LPM absorbs 180 joules of heat from a 12 watt laser over 15 seconds response time. The specific heat of aluminum is .9 J/gram Kelvin and I'd estimate that heatsink to be about 100 grams, so we have 180J=(.9)(100)(delta temp). The rise in temperature should be 2 degrees Celsius and that does not account for dissipation from the heatsink over 15 seconds or the heat that goes into electrical energy. Not to mention that who is going to have a 12 watt laser?? (And where can I buy one?! ) I could be wrong, but I bet <2 degrees can't skew the reading too terribly.

Maybe we can get a better heatsink, but I'm not all that concerned because my most powerful laser is around 3 watts

100g is a very unrealistic weight for that heatsink.

I don't know if your calcs are right or not, but I get a very different impression of the temperature rise from looking at a datasheet:
http://www.digikey.ca/product-detail/en/EA-T220-38E/EA-T220-38E-ND/2342473

Even based on your calcs, assuming the formula makes sense, but stipulating a more realistic 30g weight for that heatsink and a 60 second LPM run (which is a fairly standard run, if not a bit short, for someone trying to test a laser).

720=0.9x30(rise)
Rise = 27 degrees

If that's the correct formula to be using, that's a dramatic rise. How would that not throw off the readings ?!? That's only 60 seconds. What if you're trying to test stability over 2 minutes?

This 12W business is nonsense. If your argument is "fine, but who has a 12W laser?", then that's just more fallacious reasoning. That's like saying, "my car can go 1,600 miles per hour" and then when challenged on the spec, responding "well, there aren't any roads nearby that will let me actually drive that fast"

 

[Teej]

Re: USB Portable Powerful 12W Custom LPM "Persale Price"

100g is a very unrealistic weight for that heatsink.

I don't know if your calcs are right or not, but I get a very different impression of the temperature rise from looking at a datasheet:
EA-T220-38E Ohmite | EA-T220-38E-ND | DigiKey

Even based on your calcs, assuming the formula makes sense, but stipulating a more realistic 30g weight for that heatsink and a 60 second LPM run (which is a fairly standard run, if not a bit short, for someone trying to test a laser).

720=0.9x30(rise)
Rise = 27 degrees

If that's the correct formula to be using, that's a dramatic rise. How would that not throw off the readings ?!? That's only 60 seconds. What if you're trying to test stability over 2 minutes?

This 12W business is nonsense. If your argument is "fine, but who has a 12W laser?", then that's just more fallacious reasoning. That's like saying, "my car can go 1,600 miles per hour" and then when challenged on the spec, responding "well, there aren't any roads nearby that will let me actually drive that fast"

It could also be more like saying my car's speedometer goes to 1,600 mph....but the car can only go 120 mph, etc.

:crackup:



I get the impression that, via a third party, plenty is lost in the translation so to speak between the actual designer, and this forum.

Maybe the designer could weigh in on the technical aspects?

 

[Jstr]

Re: USB Portable Powerful 12W Custom LPM "Persale Price"

I'm not arguing with you, really just trying to discern the facts, so please don't get offended or attack me.

100g is a very unrealistic weight for that heatsink.

I don't know if your calcs are right or not, but I get a very different impression of the temperature rise from looking at a datasheet:
EA-T220-38E Ohmite | EA-T220-38E-ND | DigiKey

Even based on your calcs, assuming the formula makes sense, but stipulating a more realistic 30g weight for that heatsink and a 60 second LPM run (which is a fairly standard run, if not a bit short, for someone trying to test a laser).

720=0.9x30(rise)
Rise = 27 degrees

If that's the correct formula to be using, that's a dramatic rise. How would that not throw off the readings ?!? That's only 60 seconds. What if you're trying to test stability over 2 minutes?

Podo has told me it is actually an 80 gram heatsink. My bad.

To be clear, the following is only an (over) estimate.

The reason I used only 15 seconds is that it is before the LPM reading levels out, there is less heat dissipation from the heatsink (even that gives an overestimate for temperature). That gives 2.5 degrees for a 12 watt laser (or 10 degrees for 60 seconds, but the huge error on that makes that value meaningless).

As heat builds up in the heatsink, the rate of dissipation also increases.

Also, the above estimate does not factor in the heat that is converted into electrical energy, which is typically 5-8% (Thermoelectric generator - Wikipedia, the free encyclopedia), but can be up to 20%
(Thermoelectric materials - Wikipedia, the free encyclopedia).

The whole idea behind these types of LPM's is that there is a temperature difference between the two faces of the peltier chip. As long as there is a maximum temperature (determined not by size, but by surface area of the heatsink) and an equilibrium below a reasonable point, I believe the output voltage and current can be suitable for accurate LPM readings. As long as the specs are such to allow a linear relationship between laser power (input heat) and output voltage (in this case 1mV=10mW), the sensor can be calibrated for accurate and useful readings.

That's why the quintessential nature of a thermal LPM lies in calibration. That's why as long as this is calibrated with a reliable LPM, which it is, it should and does work.

What matters with any electronics heatsink is not the size, but the surface area. The surface area determines the rate of dissipation and how quickly the heatsink reaches an equilibrium temperature, which is what matters. That is the temperature you should worry about, but it's not going to be close to 27 or even 10 degrees.

For what it's worth, my radiant x4's heatsink doesn't get discernibly warmer even after 3 minutes at 3 watts.

This 12W business is nonsense. If your argument is "fine, but who has a 12W laser?", then that's just more fallacious reasoning. That's like saying, "my car can go 1,600 miles per hour" and then when challenged on the spec, responding "well, there aren't any roads nearby that will let me actually drive that fast"

And that's not ad hominem?

Also, Podo clearly tested it (with multiple lasers), so it's not the same at all.

 

[rhd]

And that's not ad hominem?

Also, Podo clearly tested it (with multiple lasers), so it's not the same at all.

Nope. It's valid analogy. IE, analogizing the flawed reasoning in a manner that retains the underlying logical fallacy (responding to a challenged specification by highlighting the its upper end figure isn't practical anyway).

The test he needs to do is to take a 60 second measurement, and then at second 61, move the beam to an Ophir sensor for an immediate reading, and compare.

 

[Jstr]

Re: USB Portable Powerful 12W Custom LPM "Persale Price"

Nope. It's valid analogy. IE, analogizing the flawed reasoning in a manner that retains the underlying logical fallacy (responding to a challenged specification by highlighting the its upper end figure isn't practical anyway).

The test he needs to do is to take a 60 second measurement, and then at second 61, move the beam to an Ophir sensor for an immediate reading, and compare.

Logically I agree with you, but it's not at all the same realistically because 1,600 mph is physically impossible for a car on land and 12 Watts is nothing for industrial LPM's.

The analogy is hyperbolic and insulting to both Podo and the developer of this LPM. Essentially saying "you're full of bs."

I realize I should clarify what I meant by my original statement was that I wouldn't use it for a 12 watt laser. I was in no way making the argument that "it doesn't matter what he claims because it's not practical" because a.) While it may not be practical for me, it is plenty practical to measure 12 watts, otherwise why would any respectable LPM manufacturer carry them? and b.) I wasn't arguing at all... So all this is off topic.

And I would also like to see that test.

I'm not convinced of 12 watts either. So definitely more testing videos would be nice.