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Question about LPM Power graphs?

Joe Mo

Joe Mo

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I was wondering, in the graph below you can see the power increasing over a period of about 10+ seconds. Is that a close representation of the output of the laser during that 10 second period? OR is that the LPM slowly picking up that power over the 10 second period? meaning, is the LPM DRASTICALLY under representing that lasers power over that 10 second period when the power graph is increasing exponentially.
http://img163.imageshack.us/img163/7443/635w.png
note: this is a LPM graph from yobresal's 700mW red Ehgemus build
thanks just wondering!
 
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Sigurthr

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The exponential curve at the beginning is the LPM's thermopile reaching equilibrium with the heat generated by the laser light. Your laser is likely putting out full power within a few uSec. Unfortunately lasers which have an initial high peak on power up which then declines cannot be accurately measured for their true peak power with this type of sensor, but the stable power or average power can be accurately measured.
 
Joe Mo

Joe Mo

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Sigurthr said:
The exponential curve at the beginning is the LPM's thermopile reaching equilibrium with the heat generated by the laser light. Your laser is likely putting out full power within a few uSec. Unfortunately lasers which have an initial high peak on power up which then declines cannot be accurately measured for their true peak power with this type of sensor, but the stable power or average power can be accurately measured.
Click to expand...

That's exactly what I thought! Thanks for clarifying.
 
lasersbee

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Sigurthr said:
The exponential curve at the beginning is the LPM's thermopile reaching equilibrium with the heat generated by the laser light. Your laser is likely putting out full power within a few uSec. Unfortunately lasers which have an initial high peak on power up which then declines cannot be accurately measured for their true peak power with this type of sensor, but the stable power or average power can be accurately measured.
Click to expand...

You are right on the money...
The only way to get a more realistic startup power reading is
by getting a Laser Power Meter that uses an Optical Head or
a LPM that uses a Thermopile Head with a faster response like
the recent OHPIR 20C head or the LaserBee IX or the LaserBee II.

The graph above was no doubt produced by one of our budget
LPMs like the LB-USB.

Any DECREASE in response time invariably translates into higher costs.


Jerry

You can contact us at any time on our Website: J.BAUER Electronics
 
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Joe Mo

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lasersbee said:
You are right on the money...
The only way to get a more realistic startup power reading is
by getting a Laser Power Meter that uses an Optical Head or
a LPM that uses a Thermopile Head with a faster response like
the recent OHPIR 20C head or the LaserBee IX or the LaserBee II.

The graph above was no doubt produced by one of our budget
LPMs like the LB-USB.

An increase in response time invariably translates into higher costs.


Jerry
Click to expand...

thanks jerry!
 
MarioMaster

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lasersbee said:
You are right on the money...
The only way to get a more realistic startup power reading is
by getting a Laser Power Meter that uses an Optical Head or
a LPM that uses a Thermopile Head with a faster response like
the recent OHPIR 20C head or the LaserBee IX or the LaserBee II.

The graph above was no doubt produced by one of our budget
LPMs like the LB-USB.

An increase in response time invariably translates into higher costs.


Jerry
Click to expand...

You mean a decrease ;)
 
MarioMaster

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The Alpha has been discontinued. It was our first LPM and helped Radiant establish a name, but it is very basic and was not optimized for volume production.

I'm not going to say much, but I will say keep an eye on the reviews section in the next week or two :)
 
Joe Mo

Joe Mo

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MarioMaster said:
The Alpha has been discontinued. It was our first LPM and helped Radiant establish a name, but it is very basic and was not optimized for volume production.

I'm not going to say much, but I will say keep an eye on the reviews section in the next week or two :)
Click to expand...

Wonderful! Thanks for the heads-up.
 
Bluefan

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Sigurthr said:
The exponential curve at the beginning is the LPM's thermopile reaching equilibrium with the heat generated by the laser light. Your laser is likely putting out full power within a few uSec. Unfortunately lasers which have an initial high peak on power up which then declines cannot be accurately measured for their true peak power with this type of sensor, but the stable power or average power can be accurately measured.
Click to expand...
Diode lasers within some tens of microseconds (depending on the driver), DPSS lasers can take a few hunderd milliseconds. There was a thread somewhere discussing measurements with thermal lpm's somewhere that is pretty useful, but I can't find it.
 
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