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Help with LPM wiring db25 pinout PM5200 to attach Thermopile sensor

ducatidragon916

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Hello I was wondering if anyone could help me on a bit of information i was trying to obtain regarding the PM5200 Meter . now the main reason i would like to know or get the pinout of the Laser power head detector , is because i obtained a 200 Watt Thermopile sensor on ebay and want to hook this up to the Pm5200 meter. I am guessing the reason why they use a db25 pin connector is because of the possible connections to a board in the head which would possibly contain a preamp to condition the output power of the thermopile sensor so that the PM5200 can read more accurately and stably. I also think their might be a connection to a thermistor that would help to detect the ambient temperature and allow the meter to compensate for the surrounding temperature in diagnosing the accuracy of the detected output power of the laser beam. These are all conjectures on my part so I am stabbing in the dark. It also might just as simple as attach one side of the thermopile to this pin # and the other side of the thermopile to the ground pin # etc. Any information would be appreciated on this as I feel I have been spinning in a constant chase of the nose to the tail on the internet searches etc. At one point i considered just buy a laser detector head and plug it into this meter, however I have 2 of these thermopile sensors and was hoping to just machine some aluminum and attach the sensor to this and hook up the outputs to the meter. If i have to backward engineer a unit i would do this but it would be the last resort and would rather start on a fresh page . I am assuming the output of the thermopile is like 1mv/mw calibration reference etc. If you or anyone you might know that knows the pinout on what should be connected I would really appreciate it. Please advise....Thanks!!!!
 



ducatidragon916

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In addition I think that most of these professional systems use a voltage conditioning circuit inside the thermopile sensor head. This circuit most likely involves an Sensitive low voltage Op amp instrumentation level to amplify voltage less than 10mV range. I also think that there is a reference thermistor detection in the circuit to compensate for temperature difference in the cold zone to help keep the unit more accurate when measuring the power of a lasers beam. If i could get the pinout on the db25 connector it would allow one to figure which pins to apply the signal too and supply power to the circuit etc. Once this is identified i think one could assume the connection procedures. I am hopign someone can come up with this knowledge or provide a pinout diagram to help.
 

Encap

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Little if any chance anyone on LPF has direct knowledge of the pinout of your "antique" meter or any aspect of that meter for that matter --those were from late 1980's to early 1990's.

Have never heard of anyone on LPF having or speaking of one in past 10 years.

Maybe contact Coherent who bought Molectron in 2002 see: https://www.photonics.com/Articles/Coherent_Acquires_Molectron_Detector_Inc/a14569 --they might have available a service manual or user manual.

Call them and ask: https://www.coherent.com/measurement-control/main/laser-power-and-energy-meters

Only other choice is to contact LPM repair places and see if anyone is familiar with the Molectron PM5200
 
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ducatidragon916

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May 17, 2020
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I have been busy re-engineering this meter and possible probe connection variations . I have discovered various aspects of this meter and the reading procedures of the head and what I should do in regards of using this meter and building a probe to connect to the db25 connector and use this meter. I believe this meter is quite sophisticated and is very advanced for what features it provides. When i finish the total research if anyone is interested I could provide the schematic and the photos i used to setup for use etc. I believe I am 80% done at this moment. I still in disbelief that nobody has any information on the hookup or the procedures for this unit since it was built in 1993 making the meter nearly 27 years old technology.
 




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