Correct LPM Adjusting design

[justinjja]

Here is an example:

A tec outputs 50mV when hit with 1W of energy
Should the offset be added to the 50mV and then multiplied by 20?
Or should the 50mV be multiplied by 20 and then add the offset?
Or will either way work?

Or another way to ask the question:
If my lpm is at 0mW and I twist the adj pot all the way,
the output goes up to 10mW
If I am reading 1000mW and twist the adj pot all the way,
It should read 1010mW right?

 

[Bionic-Badger]

The second question describes how it is ideally supposed to work. The offset is to compensate for ambient temperature effects that should be constant at any sensor input.

 

[Fretwrecker94]

A picture of your set-up might help too. And even if it can be said with words, I'm sure we all would like to see it anyway!

Is your TEC Heatsinked?

 

[lasersbee]

Here is an example:

A tec outputs 50mV when hit with 1W of energy
Should the offset be added to the 50mV and then multiplied by 20?
Or should the 50mV be multiplied by 20 and then add the offset?
Or will either way work?

Or another way to ask the question:
If my lpm is at 0mW and I twish the adj pot all the way,
the output goes up to 10mW
If I am reading 1000mW and twish the adj pot all the way,
It should read 1010mW right?

You got me a little confused... first... what is "twish"
Are you trying to Zero your LPM ??? Is this a functioning
LPM or is it a DIY LPM of your own design..

I would need to see your LPM circuit to know where your
pot is located in the circuit to see if you even have offset
control.

And then you would need to calibrate it to a known accurate
source to see if an offset is required and how much.

Also... depending on your Sensor coating chemistry... the
coating may not be linear from 1mW to 1000mW with a single
wavelength not to mention perhaps worse with different
wavelengths.

I'm no expert... I'm just speaking from experience...


Jerry

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

 

[justinjja]

On Mariomasters DIY LPM thread, the Image of the circuit is missing,
Is that picture avalible anywhere, It would be a good reference.

Edit Found it here, Thanks Jerry

The second question describes how it is ideally supposed to work. The offset is to compensate for ambient temperature effects that should be constant at any sensor input.

That is what I figured, thanks
I would rep you, but your sig wont let me :crackup:

A picture of your set-up might help too. And even if it can be said with words, I'm sure we all would like to see it anyway!

Is your TEC Heatsinked?

This lpm is still in my brain so it would be difficult to get a pic of it, lol

You got me a little confused... first... what is "twish"

Come on now, I was only 1 letter off.

Are you trying to Zero your LPM ??? Is this a functioning
LPM or is it a DIY LPM of your own design..

I am currently in the "design" stage of making an lpm.
I will be using an analog zeroing design, like what the Laserbee A uses.

I am working on the best placement for that potentiometer in my circuit.

Also... depending on your Sensor coating chemistry... the
coating may not be linear from 1mW to 1000mW with a single
wavelength not to mention perhaps worse with different
wavelengths.

My sensors will have a coating from thorlabs that has less than 1% variance in the visible spectrum.
I havn't tested it yet, but that is their claim.

I'm no expert... I'm just speaking from experience...

Yes you are

 

[lasersbee]

I mentioned "twish" because you posted it twice... once is a typo...

The Zero pot on the MM LPM circuit is to move the ground line
slightly to offset the output of the Op Amp if it is not at Zero.
The problem with that circuit is that if the output goes below
zero ( the Sensor Heatsink is warmer than the sensor) you can
not Zero the reading properly because it only uses a single rail
supply.

The LaserBee A uses dual rail supply that solved that problem...


Jerry

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

 

[lasersbee]

My sensors will have a coating from thorlabs that has less than 1% variance in the visible spectrum.
I havn't tested it yet, but that is their claim.

What Coating from Thorlabs (part number or link).
I couldn't find any on their site and the Thorlab Support Team
I asked last year had no knowledge of any OEM Thermopile
coatings available... :thinking:

Jerry

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

 

[piferal]

What Coating from Thorlabs (part number or link).
I couldn't find any on their site and the Thorlab Support Team
I asked last year had no knowledge of any OEM Thermopile
coatings available... :thinking:

Jerry

I do not know if this helps you.

 

[lasersbee]

Thanks for the link. I had seen that but that can not be used as
a coating that has less than 1% variance in the visible
spectrum for a thermopile sensor.

That is a Silver based electrically conductive Epoxy for places
that regular soldering is not possible.

My sensors will have a coating from thorlabs that has less than 1% variance in the visible spectrum.
I havn't tested it yet, but that is their claim.

Still waiting for a response from justinjja...
I even sent him a PM... still waiting for a response there
as well...

I had contacted Thorlabs again this week and it seems
they DO NOT sell any coating as an OEM item.
They won't even apply coatings in their coating facility
on customer supplied materials or parts..

I'm still curious what and from where justinjja got his 1%
variance coating...:thinking:


Jerry

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

 

[piferal]

No problem,

Specifically I'm talking about this product AQE32 coating, not the conductive epoxy, you agrees right?

Edit: Or I misunderstood and this product is used together with the epoxy? :thinking:

 

[lasersbee]

The AQE32 is explained in the Catalog Page: .PDF link at the right
of that page.

It is an electrical resistive coating that is water based. I says nothing
about it's thermal properties or it visible band width characteristics.

I would not use that product either as a Thermopile Sensor coating...


Jerry

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

 

[piferal]

Yes I saw it, thanks.

In no way I tell you to use with your sensors or others.

It was just to be sure that we speak the same product, and not the epoxy, that's all.

 

[lasersbee]

I hadn't seen the Resistive coating until you linked
to it. Thanks..

I would still like to hear from justinjja... maybe he
has a relative that works for Thorlabs...


Jerry

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

 

[justinjja]

For now I'm going to keep my coating a secret. :shhh:

BTW I don't have any special connections to thor labs,
just doing some outside of the box thinking...

 

[lasersbee]

For now I'm going to keep my coating a secret. :shhh:

BTW I don't have any special connections to thor labs,
just doing some outside of the box thinking...

My sensors will have a coating from thorlabs that has less than 1% variance in the visible spectrum.
I havn't tested it yet, but that is their claim.

Now you have me confused...:undecided:

Is it a coating from ThorLabs as you indicated in Post #5 or
is it your own DIY concoction as you seem to indicate now...:thinking:


Jerry

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

 

[Trevor]

justinjja, you shouldn't feel at all compelled to tell anyone what you're using.

No one else has revealed what they use to paint TEC's. 'tis only fair.

Trevor