Measuring Temperature and Light intensity with multimeter

[michelrietveld]

Hi, i know it is possible to use a PTC or NTC resistor to measure the temperature while setting your multimeter to analog voltage but i don't know the type of PTC/NTC that should be used to get a fairly adequate reading. It will be used to see if temps go up or down and to have an estimated value for the degrees in Celsius.

I also know that it is possible to do the same trick for the laser light output with a photondiode or so. Not to get exact readings but also to have an idea if it is 200mw or 900mw. Would like to use it to test if the output before and after dichros is somewhat ok.

Anyone using this and can help me identifying the parts needed?

Thanks in advance,
Michel
Utrecht
Netherlands

[michelrietveld]

Found a site in Dutch, which is my native language, describing a do it yourself power meter @ http://aartsite.nl/laser/lp_inl.htm

Will investigate and if interesting enough post my findings in English.

Michel

[michelrietveld]

Also came up with the following post on a different forum:
http://laserpointerforums.com/f42/si...ter-26341.html

but all are limited to mW instead of W.

[michelrietveld]

found attached documentation, photo cells can be acquired for little money but then....

[lasersbee]

The problem with inexpensive Photo Diodes and Photo Detectors is that
they get saturated at low powers. They also need to be large enough
to capture all of the Laser's light.
Here is an optical LPM but it is only good to 200mW.

At that power you need to take a quick reading. Higher powers also heat
up the sensor too much and falsify the results.
http://www.bauer-electron.com/index....d=7&Itemid=102

You also need an optical correction chart for different Laser wavelengths.

You can avoid all that with a Thermal Laser Power Meter....

You can use a DMM set on the Resistance scale and a NTC thermistor.
You will need to have a temperature to resistance chart for the thermistor
model you want to use..
With a NTC Thermistor the resistance will go down as it heats up..

Jerry