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Thread: Coherent power meter calibration

  1. #1
    Join Date
    Nov 2005
    Location
    Melbourne, Australia
    Posts
    3,681

    Default Coherent power meter calibration

    Hmm so I have a field max and sensor which needs calibration.

    Does anyone know what coherent charge for re calibration? I just got quoted a price by the local agent which is much higher than expected.. :-(
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  2. #2
    Join Date
    Nov 2007
    Location
    SoCal / San Salvador / NY
    Posts
    4,015

    Lightbulb

    Heya m8..

    Quote Originally Posted by dave View Post
    ..I have a field max and sensor which needs calibration. Does anyone know what coherent charge for re calibration? I just got quoted...much higher than expected..
    ..Well, that's the 'catch'.. To cal *just* the Meter, it's only about $230. (US) If ya want 'before / after' data, it's still only about $355. (total, not 'additional'..) ..*but*, to also-cal the Head, they charge separately (..it goes to a different building / dept, etc..), and whether you've got an LM-1, 10, or even a 150, it's a 'flat-rate' $250. - and that is additional. ..Ya, >_< I know.. So, in-all, you're lookin at half a G, with shipping, et al.. How does that compare to your 'local bloke'?

    ..Honestly, tho, not-really sure what there actually *is* to 'calibrate' on the sensor-side.. (??) I'll admit, I've never tried to 'RE' one / taken-apart to see what makes 'em tick, etc.. I have with Ophir-sensors, but.. those are (obviously..) not Cohrs.. Maybe P'Fesser Roberts might know if there is some 'trim-pot' or something in the LM-series heads, that can-be Cal'd.. Maybe they just measure the value of all resistors, caps, what-not, and if anything's 'off' by more than .00X%, they replace the errant part(s).. <shrug>

    ..Meter-side, sure, there's plenty of stuff to 'adjust' / tweek, but.. Sensor-side, not really-seein the 'value' of the additional $250. I could see maybe $125. or so, but.. another 250. is kinda :/ ..Maybe that's just a 'flat bench-fee', regardless.. Lemme know if I can be of help..

    cheers..
    J
    ....and armed only with his trusty 21 Zorgawatt KTiOPO4...

  3. #3

    Default

    I always thought the opposite, the meter is just some resistors and there is not much to go wrong, where as the sensor head is relying on the reflectivity of the absorptive coating, the thermal properties of the various interfaces, the thermocouple junctions, etc. Even the cheapest voltmeters can hold their calibration to 1% for decades, with modern technology you can get easily 1000x better absolute accuracy than is needed thermopile measurements.

    In any case, on the old (molectron style PMxx) heads there is a trimpot in the connector, in the newer LM sensors heads there are 4 detectors (needed for the position sensing) so the cal is all done in the data stored in an eeprom (also in the connector). They also are supposed to calibrate the sensor at a few different wavelengths (especially important for silicon detectors, but also necessary for thermopiles to keep the few percent accuracy spec), so it requires a fair bit of equipment up front and a good number of measurement points for a full cal.

    - - - Updated - - -

    I always thought the opposite, the meter is just some resistors and there is not much to go wrong, where as the sensor head is relying on the reflectivity of the absorptive coating, the thermal properties of the various interfaces, the thermocouple junctions, etc. Even the cheapest voltmeters can hold their calibration to 1% for decades, with modern technology you can get easily 1000x better absolute accuracy than is needed thermopile measurements.

    In any case, on the old (molectron style PMxx) heads there is a trimpot in the connector, in the newer LM sensors heads there are 4 detectors (needed for the position sensing) so the cal is all done in the data stored in an eeprom (also in the connector). They also are supposed to calibrate the sensor at a few different wavelengths (especially important for silicon detectors, but also necessary for thermopiles to keep the few percent accuracy spec), so it requires a fair bit of equipment up front and a good number of measurement points for a full cal.

  4. #4
    Join Date
    Apr 2006
    Location
    Miami, FL
    Posts
    3,577

    Default

    when I was speaking to Coherent about the lab master I blew up they told me they can't even cal them anymore, if you send them in for cal they check to see if it's accurate, if it is, great, if not, it's out of spec and that's the end of that meter!

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