I'm Almost Ready For 20W Speedy style!

[Speedy78]

I would have hime make it a tad bit wider than 38mm unless you have a file and can file it to make a perfect fit. Took me about 10 minutes to file it to fit. But its nice and snug now.

 

[BowtieGuy]

Will do. Mike had me PM him with the exact dim's. of my sensor.
Mine measured 38.125mm, or about .005" larger than 38mm.
Thanks for the heads-up.

 

[Meatball]

Not to detract from Jerry's skill or knowledge, but if it was designed to take higher wattage measurements by heatsinking it, I'll trust the very smart Isreali Jews who designed and built the Ophir.

That's not really what Jerry meant by "enclosure".

It is not good to "enclose" the sensor - by which you separate the sensor from the larger "system" of ambient room air temperatures which are much more stable as a thermal reference.

By adding heatsinks to the head, you increase the amount of heat that the head can allow to flow from the sensor back into the larger room "system". So yes, putting a fan on these heatsinks adds a lot complexity to the system since the heatsinks are supposed to hold the reference temperature of the room.

There must be a temperature difference between the sensor and the case of the head for a reading to be maintained. The sensor collects the heat at a stable rate, and the heatsinks on the case should sink heat back away at a stable rate - allowing them to hold their temperature and therefore a stable reading.

So yes, blowing air over the heatsinks is kind of like blowing air over the sensor itself.

A water cooled head you might see newport or ophir sell is designed to do so with stability. Its a little beyond the scope of the hobbyist.

 

[lasersbee]

Not to detract from Jerry's skill or knowledge, but if it was designed to take higher wattage measurements by heatsinking it, I'll trust the very smart Isreali Jews who designed and built the Ophir.

That's not really what Jerry meant by "enclosure".

It is not good to "enclose" the sensor - by which you separate the sensor from the larger "system" of ambient room air temperatures which are much more stable as a thermal reference.

By adding heatsinks to the head, you increase the amount of heat that the head can allow to flow from the sensor back into the larger room "system". So yes, putting a fan on these heatsinks adds a lot complexity to the system since the heatsinks are supposed to hold the reference temperature of the room.

There must be a temperature difference between the sensor and the case of the head for a reading to be maintained. The sensor collects the heat at a stable rate, and the heatsinks on the case should sink heat back away at a stable rate - allowing them to hold their temperature and therefore a stable reading.

So yes, blowing air over the heatsinks is kind of like blowing air over the sensor itself.

A water cooled head you might see newport or ophir sell is designed to do so with stability. Its a little beyond the scope of the hobbyist.

Just saw this....

Yeah you saw right though what I exactly meant...
I thought it was clear... but apparently not...

Thanks for stepping in...

BTW... I had spoken to OPHIR a few weeks ago and
the very smart Isreali Jews who designed and built
the Ophir don't even sell a Heatsink for their 20c heads.


Jerry

 

[Leodahsan]

You will also get inaccurate readings by cooling the Head/Heatsink
below ambient room temperature unevenly or with fluctuating air
currents.


Jerry

Ive read somewhere that the Ophir has some kind of compensation, so if you cool the "hot" side, it should not give an innacurate reading. It is designed for that. IIRC the accuracy lowers to 20mW

@Speedy78
Have you modified the sensor to achieve 20W? You know, the op-amps voltage swing, gain etc...

 

[EpicHam]

Ah!
So basically the heat sink is used to act as a reference temperature between the sensorhead and the spot where the laser hits.
And that rate of heat transfer from the sensorhead to the heatsink is then used to correlate the relationship between the actual power of the laser.
Since the rate of heat transfer to the heat sink is fixed.

So ,which means so as long as I don't affect the rate of heat transfer from the sensorhead to the heatsink to the surrounding ambient air.
The accuracy of the LPM would remain intact.
Yes?

 

[lasersbee]

Ive read somewhere that the Ophir has some kind of compensation, so if you cool the "hot" side, it should not give an innacurate reading. It is designed for that. IIRC the accuracy lowers to 20mW

Have you tested that your self... :thinking:
We have.

If you just touch the OPHIR head with your fingers the head
reading goes down just as it should by unbalancing the thermal
equilibrium between the sensor and the head.

EDIT
@EpicHam...
your terminology may be a bit off but yes you are basically correct.


Jerry

 

[Leodahsan]

Have you tested that your self... :thinking:
We have.

If you just touch the OPHIR head with your fingers the head
reading goes down just as it should by unbalancing the thermal
equilibrium between the sensor and the head.


Jerry

:beer: it makes sense. I didn't had any chances to put my hands on an ophir...