Kenometer Pro Review

[heroic]

yep, i am totally pulling things out of my ass

this is really all there is to a bee1

Well, just from looking at it:

- the op amp and AREF are on a separate power/ground plane from the micro
- they are connected through either a resistor or an inductor (your photo is too fuzzy to tell which)
- looks like a good quality, dimensionally stable FR4 board
- notice all the low tolerance metal film lasertrim resistors? I did
- at least 1.5 oz copper
- bridge input resistors look to be intentionally soldered to the hilt, to improve tolerance and eliminate solder degradation
- bridge input resistors placed above their own groundplane (can see it through the FR4 if you mess with the curve on the image in iPhoto)
- Small outline 6-pin device- is that a precision voltage reference? or is it the ADC? I like how it's far from the microprocessor.
- I like the decoupling design you have here.
- Layout keeps the analogue section far from the serial port and LCD drive; this helps

These are some of the things your design does not have.

[Phredy1]

yep, i am totally pulling things out of my ass

this is really all there is to a bee1

It has to look like a bowl of colored noodles to be good?

[MarioMaster]

i wish i had a better resolution image to work with

[lasersbee]

Why would you block out the Serial Number....
we have nothing to hide...

Jerry

[Kenom]

Why would you block out the Serial Number....
we have nothing to hide...

Jerry

Maybe the person who supplied the pictures didn't want to get involved?

[heroic]

Maybe the person who supplied the pictures didn't want to get involved?

I'm guessing it was you or one of the other folks in your little group, and you didn't want Laserbee to know you'd taken the meter apart and looked at it.

For reference, in future: ADCs can be really small these days. And really accurate. Like the Cirrus CS5513, say. Literally thousands of times more accurate than the crap built into the AVR, and it's a SOIC8.

[Mario]

IMHO, as an electronic engineer those meter should be not be put on sale because they are attempt of DIY design and they will not comply any international standard regarding the field of application.
As a laser hobbyist I really appreciate the effort and the passion those guys has put on the realization of these measurement equipment.

I like very much the idea of using the ophir sensor and I dislike the use of TEC glued on the heatsink.

As a suggestion try to keep the electronic as simple as possibile avoiding the use of A/D conversion especially those A/D emebedded on MCU. A cheap low drift, low noise op-amp with a galvanometer for readout (or if you like a DMM) will do the job with an accuray suitable for hobbyst usage.

Just my 0.01 € though :-)

- M

[heroic]

As a suggestion try to keep the electronic as simple as possibile avoiding the use of A/D conversion especially those A/D emebedded on MCU. A cheap low drift, low noise op-amp with a galvanometer for readout (or if you like a DMM) will do the job with an accuray suitable for hobbyst usage.

That's no good for measuring time series power readings, for example to determine stability.

You can get 24-bit metrology ADCs in SOIC8s for less than 5 euro a piece. You can put them on a separate power and ground plane, far from the uC, and you can optoisolate them. They have integrated digital filters that will reduce noise to below measurable limits. They are far, far more accurate than any galvo movement at ten times the price, and they never need to be recalibrated as they never drift. (They do need temperature compensation, but you can do this easily with a couple of ten cent temperature sensors.)

The world of metrology is a digital world now. Mostly, it's better for it.

[Things]

This is a $400 hobbyist meter! If you want your .0000001% accuracy then go splurge on one of the $>1500 meters!

@laserbee: Just saying your ADC is "Propriety" doesn't help your side, did you have THEM custom produced too??

To be honest, I don't really give a crap whether my meter reads 100mW on a laser that is doing 100.1mW, and if I did, I would be paying more than $400 for it.

I agree there is some hardware issues that could be fixed, but pointing out all these accuracy issues on a hobbyist meter is stupid IMO.

If you really care that much about your phone giving you an extra +/-2mW or whatever on your reading, then turn it off, or dont have it sitting on your meter. Sheilding is barely required, as the amp is INSIDE THE THERMOPILE. If you had the amp and thermopile seperate, then yes, use sheilding, but it's not really a problem. You may induce 1mV into the line, big deal, your reading is off by 1mW, that could even be a speck of dust that happens to be in the beam when you measure it.

I don't see why so many teeny issues are being brought up on a hobbyist meter. If you don't want to buy a Kenometer, fine, then don't, but if you don't own one, you don't really have any grounds to say what they can't do and that they don't work.

Whats the point of the enclosure? Maybe it's to make it more durable by not having WIRES hanging out everywhere? Maybe it's to make it look neater? This depends on individuals.

Sure, we can use a higher precision ADC, but why? Who gives a crap if your reading is off by .1mW.

I know I'm going to get slammed for this, but It's really unfair how all this crap is being slammed on the meter, and Kenom explaining everything, yet laserbee can sit there and say his meter circuitry is "propriety". Stop hiding behind the curtains and tell us what you are using, if you think your meter are really that special. Otherwise, I see no proof that you aren't using an internal ADC either.

[heroic]

To be honest, I don't really give a crap whether my meter reads 100mW on a laser that is doing 100.1mW, and if I did, I would be paying more than $400 for it.

5% of 5W is 250 mW, and I'd be really surprised if this thing's error stackup was even as small as 5%.