The ones with built in amplifiers like the 20c-a or 150c-a.
Spesificly how much current do the consume.

also is there a good place to buy them right now?
I see a few 150c-a's on ebay,
but I dont see 20c-a's for sale anywhere

Thanks, Justin

My Ophir head, DC-DC converters and LCD draw a combined 150mA. I don't remember exactly what the separate draw was but I thought the LCD was drawing most of it.

The big problem with the 150c-a, at least in terms of simplicity, is that there's not a direct mW/mV relationship. Errrr, that's a bad way of saying it. There's not a relationship that is a multiple of 10.

I think it's either 3W per 1V, or 1W per 300mV, something like that (from memory of the last one I looked up).

That means it's slightly more complicated to create an output display.

The OPHIR 20C heads draw ~5mA per supply rail
at 9VDC.


Jerry

You can contact us at any time on our Website: J.BAUER Electronics

Thanks

This one claims to be .1v/W
but why would .3v/W be an issue?
Wouldn't a simple voltage divider get it to a 10x multiple?
or worst case just an op amp

Sweet, thats not much at all, should be very easy to build a driver for one.


So anyone know where to get a 20c-a

EDIT: Also the 150c-a I linked to says it has a ZnSe Diffuser,
Is that an issue?

Of course you can add an amplifier to get a standardized
reading but it comes back to the most common problem...

How to calibrated the readings without a Calibrated LPM.


Jerry

You can contact us at any time on our Website: J.BAUER Electronics

If the Ophir head outputs 0.3V/W, then if you set up OpenLPM with 0.3V/W and the Arduino's internal 1.1V reference you can easily get it up and running.

Trevor

I saw a datasheet for the 20c-a and it says the minimum power is 200mW
Does that mean it is just slightly less accurate below 200mW, or it actually wont work below 200mW?

Well, I've accurately measured a 2.7mW GreeNe on an Ophir head using OpenLPM. We obviously need more data points, but I'd say it's very usable.

Trevor

I think I'll stick to the "buy one from laserbee and not have to screw with all that" incentive

We've accurately measured below 5mW with a standard DMM
connected to an OPHIR 20C Thermile running on 2 standard
9V batteries..

Just remember to precisely center the Laser's beam in the 12mm
diameter Active area of the sensor or your readings will be skewed.

The surface area of the OPHIR Sensors do not give a linear output
on different areas of the active area...


Jerry

You can contact us at any time on our Website: J.BAUER Electronics

It wouldn't matter if it were calibrated at 1v/w or 3v/w though, as long as you know the value its calibrated to. A 1/3, 1/3.333 divider or 3 / 3.333x multiplier can be made to great precision without any calibration involved.

Most resistors have 1% tolerances (and usually fall well within them), but even if you don't want to rely on that, a simple voltage meter can be used to set the exact ratio with a potmeter.

Interesting, Do you know how one of these sensors works?
Im guessing they arn't based on a simple tec?
Is that how they are able to get a reading so quickly?

It's based on the same principle (a heat differential creating a voltage potential across thermocouples), but the Ophir sensors use a thin piece of graphite as the sensitive surface. It has fairly low heat capacity and is very well heatsinked, so it's quite responsive.

Trevor

Isn't it more or less a small, around active area, surrounded by a ring of thermocouples?

The operating principle is fundamentally the same, but the mechanical construction is such that it allows faster response times and more sensitivity compared to 'ordinary' TEC's where the heat has to go from the front to the back trough the thickness of the entire element?

I may be chatting with you soon...


Untitled by tsteele93, on Flickr

Nice, where did you buy it from?

It was on eBay. Super nice guy. He had purchased a laser light show and wanted to check to see if it was up to spec. He ended up not getting this in time so he ended up not using it, thus the new in bag condition.

He also sent me paperwork on how to power it, which I haven't looked through yet and he threw in a couple of 1A 12V wall warts (nib) that he had planned to use to power it.

I just need to put together the power supply and come up with a nice box and an LED display and something that will do the conversions for me from 0.3v per Watt of laser power.

In the short term I suppose a voltmeter and some 9v batteries will work and just divide the voltage readout by 0.3

I may try that tonight with my > 2 Watt 445.