Welcome to Laser Pointer Forums - discuss green laser pointers, blue laser pointers, and all types of lasers



Laser Pointer Store

DIY Ophir LPM

Trevor

Well-known member
Joined
Jul 17, 2009
Messages
4,513
Points
113
...wasn't your Ophir sensor already verified against a recently purchased Coherent FieldMax?

Trevor
 

ARG

Well-known member
Joined
Feb 27, 2011
Messages
6,987
Points
113
...wasn't your Ophir sensor already verified against a recently purchased Coherent FieldMax?
Yup, so I guess in an indirect way it has been proven to be 10% against a Coherent Fieldmax ;)
 

lasersbee

Well-known member
Joined
Sep 20, 2008
Messages
17,505
Points
113
...wasn't your Ophir sensor already verified against a recently purchased Coherent FieldMax?

Trevor
I'm not saying that the LaserBee could not be off. It could very
well be.

I hope that other Feildmax wasn't off by as much as your Brand
New Cube Laser from Coherent was off....
At that time you swore that the LaserBee was under reading until
you found that it was your Brand New Cube Laser that was off...:yh:

Just saying....


Jerry

You can contact us at any time through our Website: J.BAUER Electronics
 
Last edited:

Trevor

Well-known member
Joined
Jul 17, 2009
Messages
4,513
Points
113
I hope it wasn't off by as much as your Brand New Cube Laser
from Coherent was off....
At that time you swore that the LaserBee was under reading until
you found that it was your Brand New Cube Laser that was off...:yh:

Just saying....


Jerry
I think that was probably the reason Coherent had it lying around in a lab... :)

Trevor
 

MarioMaster

Well-known member
Joined
Jul 27, 2007
Messages
3,643
Points
63
My Coherent Fieldmax was purchased directly from Coherent and has associated calibration and accuracy certificates. It has also agreed with all other professional LPMs I have compared it to, so while Trevor's nice gift from Coherent may not have been factory fresh I have no doubts as to my Fieldmax's accuracy.

It wasn't cheap but it's good to have a definitive answer as to what is accurate and what is not.
 

Blord

New member
Joined
Dec 24, 2007
Messages
5,368
Points
0
Okay, enough talk about accuracy. The Ophir sensors are good enough for the hobbyist.
No need to show who **** is the largest. :D

I took a LPM graph of some of my lasers.
The 300mW Mitsubishi diode in the C6 host. It has a AMC7135 5-mode driver with 700mA at full. Interesting to see that low and med output is perfect stable. The laser struggles on 700mA. Easy to see the drop in power in high and also noticeable the dips when changing the modes.



The Opnext 170mW single mode diode in the Ehgemus host. This diode like it when warm. The output peaks at 30sec. Usually laser diodes peaks right after the start.



The Dominator laser with a super efficient M140 diode at 1.8A. Stay above 2.5W mark for whole 5 minutes. Quite a boring graph. :D
 
Last edited:

nospin

New member
Joined
Feb 13, 2010
Messages
182
Points
0
I see you guys need a little help

Good work on all the builds I saw! Nice clock as well Blord!

I know the details on calibration for the Ophir thermopile

Using the nice pic ARGLaser posted!

P1 to the right of the connector is calibration, it was last set in Israel by Ophir
In all the units I've worked with the most its ever off is 2 or 3mw!
no reason to touch that unless you have the proper equipment

P3 is response time don't mess with that either, no gains to be had here

P2 at the bottom is zeroing, its not easy to adjust, the key is to not have any energy exposed to the sensor when you adjust this, I usually put it face down in a small baggie on the bench carpet square, bright light sources, heating or AC vents,
even you! any energy sources will read on this sensor!

Its very touchy to adjust P2 I use a plastic RF adjusting tweeker, It has capture side I like

This is a fantastic sensor and it makes your LPMs work like $1000 units

I'm glad I could help!


I did a lot of reading on these when I got involved in this, and this is a collection of some of my old posts
that will explain in more detail whats going on


Thermopile info from LPF threads:

When its thermal environment changes the readout will show a reading because it is a reading! the heat sink is big and until it reaches the air temp in the room its in that's a measurement.
All thermopiles measure the difference in energy between the absorber and the heat sink. when you touch the heat sink or shoot a laser at the absorber that is whats measured.
If you hold your hand in front of the sensor or have hot or cold drafts hitting the sensor its going to take a reading.When there is no energy moving around the sensor, No reading

The Ophir thermopile head has a very smart amplifier circuit that measures only the power radiated onto the broadband absorber in relationship to the conduction cooled heat sink. This means that just like in $1000+ Laser Power
Meters If you hold you hand in front of the absorber you are radiating energy and that results in a measurement ( usually a few mw's ) and if you cool or warm the Heat sink it does the same effect. Within seconds the thermopile equalizes and
your back at zero. Thus no need for a zero adjustment knob!

The Thermopile is a very sensitive device, it consists of the absorber which is a very thin graphite disc with a broadband coating on it that absorbs energy over a wide spectrum "190nm to 20um in this case" Behind this disc are junctions of dissimilar metals or semiconductors usually Bismuth-Antimony. And on the other side of the junction is the cold side or the heat sink. When heat is applied to the absorber side a voltage is generated by this temperature offset this is called the Seebeck-effect. This voltage is directly proportional to the radiation on the absorber, then it is amplified and is now measurable.

When the Thermopile is fully temperature equalized and no voltage is being generated the amplifier is zeroed out in calibration to show no voltage.
Once this is done every time the sensor is equalized and no voltage is generated the meter shows a reading of zero.
If the amplifier is of the highest quality this is easily repeatable within usually 1mw every time


when you touch the heat sink or heat the sensor disc you are speeding up the equalization of temperature
difference between the sensor disc and the sink by changing the temperature of one of the junction sides
It doesn't effect the final value, that is achieved with a fine calibration adjustment.
Whether you touch it or not when you stop effecting the difference between the two sides it will eventually settle to the calibration setting.

Nospin
 

ARG

Well-known member
Joined
Feb 27, 2011
Messages
6,987
Points
113
That was a good read, and I learned some things! Thanks nospin!
 

Blord

New member
Joined
Dec 24, 2007
Messages
5,368
Points
0
Thanks for clearing things up. My Ophir was reading 2-3mW when equalize. I have only zero it with the P2 pot. A slight touch was enough to make it 0000.

This is the picture nospin is talking about:
 

nospin

New member
Joined
Feb 13, 2010
Messages
182
Points
0
The sensor can measure up to 5 watts on its own
20 watts with a heat sink "BUT AT 10mw RESOLUTION" with part changes on the board

Keep that in mind for the future when were blasting 8 watt handhelds!
 




Top