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FrozenGate by Avery

Anything Wrong With This LPM?

HighPowerObsession said:
Yeah I saw the key but had no idea what those codes meant, but ok they are sensors Thorlabs sells which are far too expensive for me.
Basically though, that graph has nothing to do with the sensor I'm looking to get.
Click to expand...


The point of the graph was to show that thermal sensors don't vary much in accuracy over the visible spectrum, although they do vary a small amount. So it was relevant, as is shown by a similar graph posted above that is for the sensor in the eBay listing.
 





astralist: Ok now THAT is what I'm looking for, thank you very much for doing all that research bro. So we are basically looking at a 8-9% error margin. So why does the data sheet say +/-3%??

diachi: Alright thank you for posting that graph.
 
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Even a 20w laser can be tested on a 5w meter.

With the right piece of glass or mirror to reduce it by a known percentage.. therefore all meters are relevant as someone else has already mentioned.

I wish you well with that meter, I looked at them as well but decided against it for lack of features. Goodluck!

I can say without a doubt I'd try to buy a Ophir from Astral before this unit.
 
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Thats an interest and smart way of thinking about it, but I would rather just get a meter that can test the output of what I am using without having to worry about percentages and stuff.
 
HighPowerObsession said:
astralist: Ok now THAT is what I'm looking for, thank you very much for doing all that research bro. So we are basically looking at a 8-9% error margin. So why does the data sheet say +/-3%??
Click to expand...

From where did you get/conclude the 8-9% number??

All you need to know about the accuracy is that 3% thing.

The spectral absorbent data is only for knowing that it is flat enough so that when you measure some wavelength, the sensor will give you flat result without favoring some wavelength.

For example, if absorptivity at 445nm is 90%, while absorptivity at 808nm is 95%, thus when you measure true 100mW of 445nm (sensor is outputting 100mW), you'll get a 105.55mW when measuring a true 100mW 808nm (sensor is outputting 105.55mW, from 100*95/90).

More absorption means more voltage come out of sensor.
This spectral absorption is essentially what they actually calibrate at factory and at NIST.
 
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Maybe I don't understand that graph then. The line for the surface absorber is right above the 90% mark which would mean that 8-9% of the light is reflected so that light wouldn't be picked up on by the sensor...

Also somewhere back in this thread someone (maybe you) mentioned that the PM-10 sensor is used or something like that. The Ebay listing says new, but is that sensor used??
 
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HighPowerObsession said:
Maybe I don't understand that graph then. The line for the surface absorber is right above the 90% mark which would mean that 8-9% of the light is reflected so that light wouldn't be picked up on by the sensor...

Also somewhere back in this thread someone (maybe you) mentioned that the PM-10 sensor is used or something like that. The Ebay listing says new, but is that sensor used??
Click to expand...

It's calibrated to account for that ~10% loss. So no, that light isn't picked up but the meter is calibrated to give an accurate result in spite of that. It doesn't need to absorb all of the light to work.

It's not used, I think what you're thinking of is someone mentioning that the calibration could go oit with use.
 
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Oh ok that makes alot of sense, thanks Diachi. How long do LMPs last before needing to be calibrated again and how can you even tell when your LPM needs to be calibrated again?
 
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HighPowerObsession said:
Oh ok that makes alot of sense, thanks Diachi. How long do LMPs last before needing to be calibrated again and how can you even tell when your LPM needs to be calibrated again?
Click to expand...

LPM*

And only a good reference laser (exactly strictly a power rating.. like a HeNe..
Since a way of estimating via a heated TEC or the like would destroy the sensor in question that wouldn't work.

Obviously if you test a laser once at full charge ad few weeks later at full charge it's half the output you either damaged your laser (lens,diode,driver,battery) or the calibration is off..

Nonetheless since you are a hobbyist I wouldn't worry about calibration as much as available features and the usability of it. also consider being able to store it away safely, or using it on the go.. many other important things to consider than recalibration.
 
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Critical Info:

see the listing on eBay, there is this sentence:
"It has a pot inside you can adj to what you like"

Looks like the seller thinks that it's "adjustable what you like" but this can actually broke the calibration.
If he's been tampering the pot, then i guess it's a no go.
 
astralist said:
Critical Info:

see the listing on eBay, there is this sentence:
"It has a pot inside you can adj to what you like"

Looks like the seller thinks that it's "adjustable what you like" but this can actually broke the calibration.
If he's been tampering the pot, then i guess it's a no go.
Click to expand...

Yeah I saw that too, but I don't know enough about LPMs to know what that pot thing is, but I'll definitely ask him if he has ever tampered with it.
Thanks for bringing that up.

I asked the seller if this unit is used and he replied with this: "I designed and built the heads for Molectron and what I have is NOS stock left. You purchase what make you feel good."
What is a NOS stock? I can tell the seller is getting annoyed which is a huge turn off for me since I have the right to ask questions about something thats gunna cost me $325.
 
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HighPowerObsession said:
Yeah I saw that too, but I don't know enough about LPMs to know what that pot thing is, but I'll definitely ask him if he has ever tampered with it.
Thanks for bringing that up.

I asked the seller if this unit is used and he replied with this: "I designed and built the heads for Molectron and what I have is NOS stock left. You purchase what make you feel good."
What is a NOS stock? I can tell the seller is getting annoyed which is a huge turn off for me since I have the right to ask questions about something thats gunna cost me $325.
Click to expand...


NOS = New Old Stock

Quick google would have told you that...
 
Diachi I do 99% of my research on my own without asking people questions so sorry if I ask one question that I might have been able to find out by searching it on my own.
 
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