Coherent FieldMax 2 power meter buying advice

Hi Guys,

I'm about to bite the bullet and buy a Coherent FieldMax II TO power meter.

I'm pretty well set on buying this meter. I've considered their PowerMax USB sensor/meters with the meter built into the USB plug but with the minimal price difference after buying a PC/netbook/tablet to run the GUI software I'd rather use a dedicated meter for portability.

With Mccarrot's advice in a previous post I'm looking at buying a PM3 sensor so I have the sensitivity to do MPE measurements and use a neutral density filter if I want to measure the full power of around 5-7.5Watts RGB.

I have made a couple of inquiries with Margaret from Coherent Australia in the last year.

After explaining my application she suggested using the OP-2 VIS sensor which is a sensor with a silicon photodiode.
This sensor has a optional 1000:1 attenuator so it can measure up to 5watts.

http://www.coherent.com/downloads/Pa...vA_1%20(2).pdf

I understand optical sensors can react much faster but what are the benefits and disadvantages in using this sensor for MPE measurements with this meter verses a PM3 sensor?

Would this allow me to measure a scanned beam and have it displayed as Watts/cm/2?

Can anyone who owns a FieldMax II TO give me any insights to what is possible when using it with an OP-2 VIS sensor?

I've been reading up more on MPE measurements and calculations and it's starting to become clearer but nothing can beat hands on experience and wisdom from the PL clan.:cool:

Any advice or thoughts to help narrow down the best sensor or sensors would be greatly appreciated.

Thanks.
Kit:)

I have one of the OP2 sensors, and it does work very nicely, although I would not recommend it in an application where you expect to have multiple wavelengths--because you need to tell the meter what wavelength you are measuring with all photodiode based sensors. If you are trying to measure both 630nm and 440nm your measurements will be off by a significant amount.

Good point there. The OP2 wont be much good for doing MPE measurements of a full colour laser.

Hi Krazer and Dave,

Thanks very much for that valuable info, it is a real big help:cool:

I'm starting to feel confident that I'm getting close to the right purchasing decision.

So, it sounds like an OP-2 sensor would be a supplimentary rather than the only sensor I'd need for my application.
Damm! I knew it sounded too good to be true:rolleyes:

OK so a PM3 is what I need to measure static RGB beams for MPE measurements.

Now if I want to measure the scanned pulse duration as it passes the eye,
I'll need a silicon photo diode based sensor/detector right?

Coherent sometimes have discount packages including this sensor or maybe if I could find a well priced second hand
OP-2 Vis I could use it for this purpose and connect the analogue output of the meter to an oscilloscope to view the pulse duration.

Does this sound like a reasonable idea?

Or is it an extravagant waste of a good sensor?

I'm trying to think how to get the most use out of the meter and reduce the amount of devices I'd need to juggle at one time when doing MPE measurements.

Can the software that comes with the meter easily show you the pulse duration of the scanned beam as it passes the OP-2 sensor?
If so I could eliminate the need for the oscilloscope.

Then I'd be back to holding a meter, two sensors and a net-book....grrrrO_o

Maybe it may make more sense to buy the PowerMax USB versions of the sensors with inbuilt meters so I can plug them both into a winXP net-book and not bother with buying the meter.

Do you use your FieldMax II to do MPE measurements? If so what setup do you use?

Sorry for so many questions:rolleyes:

Thanks
Kit:)

Dear Kit,

Before you go and buy the Coherent products, please check out the Ophir products. I'm actually our Power and Energy Meter Specialist.

We have a 12A that can measure all the way down to below a mW and up to 12W. It has a dual sesnor that cancels the background ambient temperature. This is what allows it to measure below 1 mW. Ordinarily thermopile sensors in the power range are only good down to about 10 mW. We also have a series of 3W sensors that can measure down to 50 uW, but since you need to go to 5 Watt, a thermal detector is probably your best choice.

Photodiodes sensors have their place since they 6 orders of magnitude more sensitive than thermal sensor, however using one a 5W even with an attenuator is not the best approach since most ND filters will thermal lens and then crack above ~1W. Some reflective filters can handle a little higher power, but then there's that nast reflection to worry about.

You mentioned also the need to measure a scanned beam. As far as I know Ophir has the only Scanned Beam Sensor, model BC-20. It has special circuitry buit-in for measuring the scanned beam.

If you already have the net book you can plug in any of our sensors into a small USB module called a JUNO, that is relatively low cost compared to displays. This makes it so the sensors are plug and play with either the net book or if you decide later, one of our displays. Our comparable display would be our Nova II.

Please visit our web site at www.ophiropt.com

I'm sure our Australian Representative, Raymax, would be happy to talk with you about this or even come and demonstrate something.

Cheers,
Burt

Hi Burt,

Thanks for the detailed info. It's all helping to give me a better idea of what's possible.

The reason I've been looking at the FieldMax II and it's compatible sensors is because several of our friends and regular users have them and it's very handy to compare notes with people who have the same equipment being used for the same tasks.

Thanks for the heads up, I'll be sure to have a look at your link.

Kit:)