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LPM with Ophir Sensor from nospin - Awesome!

nospin

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No

once the amplifier is calibrated to the head with a high quality op-amp circuit
continual calibration is unnecessary.

At first I was talking in general Thermopile terms, within 1mw is the repeatability with this head

Jim
 



Trevor

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No

once the amplifier is calibrated to the head with a high quality op-amp circuit
continual calibration is unnecessary.

At first I was talking in general Thermopile terms, within 1mw is the repeatability with this head

Jim
So it's a calibrated head.

(And repeatability of what?)

-Trevor
 

nospin

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Yes the head is calibrated

The repeatability of showing no reading when there is no radiation on the absorber

Jim
 

Trevor

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Yes the head is calibrated

The repeatability of showing no reading when there is no radiation on the absorber

Jim
...which is a restatement of the fact that it is calibrated, correct?

-Trevor
 

ninja_tux

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Definitely an interesting meter! Nice review Jay! If I read correctly they are $250 and can be painted as per the request of the customer?
 

ninja_tux

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Doh! I should have checked for a FS sale first *facepalm*... Thanks for the link Jay! I agree, I think for $285 this is a great deal for a 5W calibrated LPM with 1mW increments. The only feature it's really lacking that the other hobbyist meters (notably the LaserBee and both Kenometers) have is a data output for logging; which, IMO, isn't really a necessity for most hobbyists.
 

jayrob

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I read that he was working on a data logging option, but I don't know if it is still in the works or not...

I personally don't use data logging, even though my Coherent has it.

If fact, I didn't need this meter. But after I had it in my possession for the review, I wanted it!

It's so small, and also very portable. He really does nice clean work...
 

Kenom

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Laserbee, would you check to see if touching the outside of your thermopile causes it to zero quicker when on. I've noticed that when there is a slight variation in the reading, just touching the outside of the head will cause it to go back down to zero. You can then remove your hand and it will stay at zero.

This is the exact same thermopile I use in the Kenometer Pro's and USB's and it does not autocalibrate.



As you can see there is no connection going to the inside of the head other than to the junctions on the thermocouples.
 

jayrob

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As I had mentioned, I'm no expert on the inner workings... So when I said it 'zero's itself, I just meant that it goes to zero in different conditions or environments... (not re-calibrate)

Let's hope it doesn't need re-calibrating!

But I did notice a similar effect that you mentioned Ken... If it's a little slow going to zero, you can point a laser at it for a second. (and then turn the laser off) Then the meter will go to zero quicker...
 
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nospin

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Here is what its doing
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.

Jim
 
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lasersbee

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@ Kenom...
Yeah.. I've noticed that.. but I find the heatsink mass
detects my (quickly touched and removed) finger's heat quite
fast... goes from +3mW to -2mW then back up to 3mW..
It changes a bit too quickly to account for the quickly added
heat of my finger to travel through thew heat sink mass and
register a change on the thermopiles..
It seems more like an electronics induction effect...

@nospin....

Here is what its doing
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.

Jim
I just did a test with a tested 10mW Laser... The OPHIR 20C-A head
reading stabilized at +3mW and when the 10mW beam was put on the
sensor it read 13mW...
IMO... it is important to zero the meter before taking a measurement
if the reading is not at Zero without an input to the sensor.

I don't understand what you meant by that is achieved with a fine calibration adjustment.
Are you saying that you doing a fine calibration adjustment of the OPHIR heads... :thinking:


Jerry
 
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nospin

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@ Kenom...
I just did a test with a tested 10mW Laser... The OPHIR 20C-A head
reading stabilized at +3mW and when the 10mW beam was put on the
sensor it read 13mW...
IMO... it is important to zero the meter before taking a measurement
if the reading is not at Zero without an input to the sensor.

Jerry
Exactly Jerry!

The signal from the thermopile is very small and is a fine balance between positive and negative voltage "when you are near the zero mw range of the sensor" Your thermopile is evidence that with all thermopiles the output voltage is directly proportional to the radiation on the absorber.
your 20C is only off on the zero adjustment.

Jim
 
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Kenom

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There is nothing in my opinion special about this meter. It is essentially an almost exact clone of my Kenometer Lites that I was selling for a lot cheaper. The enclosure utilizes a cheezy looking wood grain, that looks like my alarm clock. Granted my enclosures for the lites weren't all that special, but my meters weren't highly elevated like this.

The head does not auto zero. I know, I've got a ton of them. As a matter of fact, you got yours from the exact same source I did, which now that they are all gone, I'm not afraid to reveal. EBAY.

Ya gonna copy the pro and usb next?
 




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