Review of the new 15W LPM from LPS....

[Benm]

2) I understand that the Laser beam that you used
in this test were Unfocussed to just fit in the 12.5mm
sensor window opening.

The video doesn't show much due to overexposure and all, but i guess this requirement is key.

I don't expect a LPM to survive unschaved when doing something stupid like focussing the beam to a pin prick onto the sensor surface.

But requiring the divergence to be set such that it matches htting a sensor area fairly big is, imho, also too much.

It should work when you focus the laser to infinity, perhaps with a beam diameter of 5 mm or something in that order. Not all laser pointers even have adjustable focus, and those that do not generally are set for the lowest divergence at infinity.

This makes a huge difference in power density, especially with multimode lasers where the output close to the laser is a line (opposite orientation to that projected line in the far field due to slow and fast axis).

So it would be fairly realistic that under real world test conditions the laser would illuminate something like a 5 x 1 mm area on the sensor surface, and certainly not evenly lite the whole sensor area, ever.

You'd be putting most power onto a 5 mm2 area instead of something like >100 mm2 for the whole sensor, and the coating must resist this.

 

[lasersbee]

The video doesn't show much due to overexposure and all, but i guess this requirement is key.

I don't expect a LPM to survive unschaved when doing something stupid like focussing the beam to a pin prick onto the sensor surface.

But requiring the divergence to be set such that it matches htting a sensor area fairly big is, imho, also too much.

It should work when you focus the laser to infinity, perhaps with a beam diameter of 5 mm or something in that order. Not all laser pointers even have adjustable focus, and those that do not generally are set for the lowest divergence at infinity.

This makes a huge difference in power density, especially with multimode lasers where the output close to the laser is a line (opposite orientation to that projected line in the far field due to slow and fast axis).

So it would be fairly realistic that under real world test conditions the laser would illuminate something like a 5 x 1 mm area on the sensor surface, and certainly not evenly lite the whole sensor area, ever.

You'd be putting most power onto a 5 mm2 area instead of something like >100 mm2 for the whole sensor, and the coating must resist this.

I agree.... 5mm2 is a beam of ~2.5mm diameter and
we tested that 15W coating at a 3mm diameter beam
when it smoked/damaged the sensor coating. The same
Max Power Test procedures we use on our own LPM
products.

BTW the manual states that you must unfocus a Laser
beam or the coating will smoke... Doesn't have specific
numbers as to how far to unfocus. The Sensor opening
is 12.5mm diameter and I used 12mm diameter for the
ambiguous unfocusing size for the calculations of the V2.

Jerry

 

[Mosc007]

My Unit has arrived. I must say it does look nice. It's as pity it has problems.

Looking at the coating on the sensor it doesn't look good. Firstly it looks like it's just some black Enamal. It's slightly reflective and is probably very unlinear. Second thing the coating has been very poorly applied. It's very uneven like it's been done with a brush.

I havn't tested it yet. But from what others have said I will keep the power low. Once the coating is burnt the calibration will be way off.

 

[lasersbee]

My Unit has arrived. I must say it does look nice. It's as pity it has problems.

Looking at the coating on the sensor it doesn't look good. Firstly it looks like it's just some black Enamal. It's slightly reflective and is probably very unlinear. Second thing the coating has been very poorly applied. It's very uneven like it's been done with a brush.

I havn't tested it yet. But from what others have said I will keep the power low. Once the coating is burnt the calibration will be way off.

Yeah... It is usable under 4 watts to protect
that badly applied non-broadband coating.

Also.. don't leave a Laser higher than 1-2 watts
on the sensor for long periods or it will skew the
readings due to the puny heatsink attached to
the TEC sensor/plate heating up inside the
enclosure where it can't get any cooling.

Jerry

 

[GSS]

Looking at Tommy's U tube video, i'm seeing it's taking quite a while for the measured power to drop after the laser is removed..
Is this from the coating still smoldering or the lack of a good heat sink on the sensor your mentioning?

 

[lasersbee]

Looking at Tommy's U tube video, i'm seeing it's taking quite a while for the measured power to drop after the laser is removed..
Is this from the coating still smoldering or the lack of a good heat sink on the sensor your mentioning?

It's due to the Hot sensor not finding it's
equilibrium temperature... There is no way
to transfer the heat on the rear plate of
the TEC since it is mounted with Rubber
Silicone instead of a thermal epoxy as any
LPM designer/builder knows.
Any heat that does make it to the small
heatsink is then trapped in the enclosure.

LPM building Rule #1...
Do Not Enclose The Sensor Head to allow
for heat dissipation and to keep it at an
constant ambient temperature....


Jerry

 

[Benm]

I'm not overly convinced that thermal compound has to be bad though. There are thermally conductive compounds on the market that set into a sort of rubbery state but conduct heat fairly well... at least if you use it in very thin layers like you would heat conductive paste.

Another question is how much heatsinking is actually required: you bascially measure the temperature difference between the sides of the TEC, so if the cold side warms up a bit, so will the warm side at continuous laser power.

If this amounts to only a few degrees nothing will change in the reading.

Realistically this type of meter should also display -negative- power when you remove the laser light and the heatsink is now warmer than the sensor surface. I know this is prevented in software in virtually all such meters, but if you look at the raw voltages from the TEC it's there.

Biggest worry is the coating though - it could be okay for lasers up to a watt or two focussed to infinity with a reasonably wide beam, but the 10 or 15 watt claim is not realistic in practical application.

I'd say realistic use of an LPM would be someone grabbing some blu ray diode, putting it at a module, focus an infinity and measure it like that. You need a pretty good coating to deal with that though, at a few watts the light is intense enough to light a cigarette at close range.

 

[lasersbee]

I'm not overly convinced that thermal compound has to be bad though. There are thermally conductive compounds on the market that set into a sort of rubbery state but conduct heat fairly well... at least if you use it in very thin layers like you would heat conductive paste.

Another question is how much heatsinking is actually required: you bascially measure the temperature difference between the sides of the TEC, so if the cold side warms up a bit, so will the warm side at continuous laser power.

If this amounts to only a few degrees nothing will change in the reading.

Realistically this type of meter should also display -negative- power when you remove the laser light and the heatsink is now warmer than the sensor surface. I know this is prevented in software in virtually all such meters, but if you look at the raw voltages from the TEC it's there.

Biggest worry is the coating though - it could be okay for lasers up to a watt or two focussed to infinity with a reasonably wide beam, but the 10 or 15 watt claim is not realistic in practical application.

I'd say realistic use of an LPM would be someone grabbing some blu ray diode, putting it at a module, focus an infinity and measure it like that. You need a pretty good coating to deal with that though, at a few watts the light is intense enough to light a cigarette at close range.

I checked the white silicone used to hold/hide
the inside of the 15W LPM. It is the same as
was used to glue the TEC to the heatsink...
As far as I know Silicone rubber is a far cry
from proper Thermal Epoxy designed for such
a purpose.

The size of the Heatsink is very important to
keep it's temperature at ambient temperature
and allow any transferred heat from the active
sensor surface to dissipate to the surrounding
ambient temperature air before the sensor can
heat it up to skew the differential readings.

Our 10W Newport Thermopile aluminum head
weighs 155 gr. and measures 36.25mm thick
and 63mm diameter...

I'm convinced that if a 10W Sensor could be
built smaller... a commercial LPM manufacturer
would have done so.

That puny little heatsink insulated inside an
enclosure can not and will not dissipate any
accumulated heat tranfer from the sensor and
just skew any readings.

Yes... Thermopile Sensors do go under 0.000mW
if first heated with a high powered Laser and let
cool.... Or the if the Head heatsink is heated.
(That's why you should not touch a Thermopile
Head with your fingers when reading power)
Since there is no MCU or Electronics to Zero the
15W LPM... that again will skew the readings...


Jerry

 

[tommy]

coating after test:

This is the final update we post here. The Pocket LPM has perfectly sustains 10w laser and keep a good accuracy. and the coating keep smooth.

We keep providing pictures and videos here, not to satisfied some one, but just to show how solid this LPM is to those LPM members/ non members who keep silent.

This LPM get a lot of support from some LPM members, non members, through pm, email or other ways. your trust will not be waisted.

Any further questions pls contact us from our site.

 

[lasersbee]

This is the final update we post here. The Pocket LPM has perfectly sustains 10w laser and keep a good accuracy. and the coating keep smooth.

I am a customer that is not satisfied with yiour
outrageous claims of Max Power for your toy LPM.

I have explained above the only way to get a 10
Watt Laser beam onto the sensor without burning
the sensor. You must unfocus the beam to 10-12mm
diameter.

If we used the same fraudulent/false advertising
practices as you with our 5.2W LaserBee AX3 LPM
product for example... we could advertise our
LaserBee AX3 at 46W Max.


Jerry

 

[Alaskan]

I kept coming back to see this, was hoping you might add a few words

:spank:op:op:

 

[lasersbee]

I kept coming back to see this, was hoping you might add a few words

:spank:op:op:

Just logged on....:crackup::crackup:

Jerry

 

[GSS]

How many repeated cycle's do you see this meter going through before breakdown?
From laser measurement's and battery recharges..

I realize at this point it's somewhat stupid question but i'm throwing this out there to Tommy and all who might chime in..

 

[lasersbee]

How many repeated cycle's do you see this meter going through before breakdown?
From laser measurement's and battery recharges..

I realize at this point it's somewhat stupid question but i'm throwing this out there to Tommy and all who might chime in..

Actually while doing the tests for the review..
the 2nd time I charged the internal battery..
the silicone glued in charger died...

Jerry

 

[Alaskan]

China junk.

 

[GSS]

Actually while doing the tests for the review..
the 2nd time I charged the internal battery..
the silicone glued in charger died...

Jerry

As Tommy and you aren't the best of friends:eg: :crackup: for a 3rd party option lets see if Lifetime is up to the challange of putting his meter through it's paces
We can start the betting in the mean time:beer: