For the PAR inclined . Apogee upgraded sensor

[oreo57]

For those that own one..

http://www.apogeeinstruments.com/mq-...upgrade-offer/



for those that don't but may want to get one in the future:
Data sheet:
http://www.apogeeinstruments.com/con...spec-sheet.pdf

significant corrections in the blue and red response..

[theatrus]

Good find.

For those with just the sensors (why buy another special purpose multimeter), it looks like the new output is 0.01mv (100x mult), where the old one had a much higher output at 0.2mV (5x mult). Thats an order of magnitude less signal level, so if you're multimeter has a terrible low end range you may have issues.

[oreo57]

Hey, just the person to ask..
When I was researching for a DIY PAR sensor one thing always came up.
Photodiodes do not really have a good linear response in the voltage domain..
Especially when unbiased, as most seem to be..
http://in.ncu.edu.tw/ncume_ee/datash...nalsemicon.pdf
Best to use the current output. Much more linear. Of course I believe the amplification was an issue..

Thoughts???

forgive my ignorance on this or trying to simplify a complicated problem..

My original thought was to use a very fine amp meter..
http://www.electroschematics.com/653...meter-circuit/

Yea it all sort of boils down to the same thing..

sorry just a curiosity point of mine..
In other words:

Photodiodes generate a current proportional to the light that
strikes their active area. Most measurement applications
involve using a transimpedance amplifier to convert the
photodiode current into an output voltage

does one need to bother w/ the conversion and asst. problems? Can't one just measure the current alone??
http://www.analog.com/media/en/techn...gn-MS-2624.pdf

This is kind of funny..
http://amasci.com/emotor/nanoamp.html
C

ommon digital voltmeters (DVMs) can measure nano-amperes. How?!! Just misuse them: use their voltage setting to measure current.

My DVM (digital voltmeter) has a 200 microamps setting, but some sorts of electrostatic effects deal with currents far below 1uA. My old 20uA panel meter is better for this, but sometimes I want to see things which barely budge its needle. I discovered a setting on my DVM meter which is 10,000 times more sensitive! The 200mV range on my DVM is also a 20 nanoamp current meter.

Sorry far off the orig. field...

[oreo57]

bump for the Apogee part..

[theatrus]

I ordered one, will have to experiment with the response.

Photodiodes are more accurate in current mode, and I imagine the "amplified" models (not yet in the SQ-500 line) would have an integrated transimpedance amplifier.

As it stands, most (cheaper) multimeters have a 100uV resolution (and a few counts of accuracy), this puts the SQ-500 readings at about +/- 20-50 PAR due to the very low signal levels (which is a lot for a reef tank). Unless your meter has a high resolution or 10uV mode, it will need an amp. I'm working up a low cost one of those you can just strap on top of the multimeter, and read direct millivolts to PAR (which easily gets you 1PAR of resolution). If there is interest, I'm sure I'll have a few spares to send off. Apogee charges an extra $200 for their rebadged multimeter

[theatrus]

Example formfactor:



The right hand has a screw down terminal block for the sensor. The two big holes have banana jacks pointing downards. Slip it into any cheap multi-meter and go. The battery and op-amps are on the back side.

[alton]

This is awesome, thanks

[USC-fan]

They want $300 just for the sensor?

[oreo57]

Originally Posted by theatrus

If there is interest, I'm sure I'll have a few spares to send off. Apogee charges an extra $200 for their rebadged multimeter

def. have interest!!!

[theatrus]

Noodled up something this evening:

Basic overview:

MAX9617 op-amp with 100x gain. This is a chopper op-amp with low input offset voltage, at maximum specification (10uV) this is +1PAR on the output signal. Typical is rated around 1uV, so 0.1PAR.

LMV321 op-amp to make a virtual ground.

CR2032 battery. Cheap and plentiful. Lots of runtime for the amplifier.

Terminal block for the sensor.

Two banana plugs (not modeled) for the multimeter connection on standard 0.75" headers.

On/off switch (not modeled)

[gus6464]

Originally Posted by theatrus

Noodled up something this evening:

Basic overview:

MAX9617 op-amp with 100x gain. This is a chopper op-amp with low input offset voltage, at maximum specification (10uV) this is +1PAR on the output signal. Typical is rated around 1uV, so 0.1PAR.

LMV321 op-amp to make a virtual ground.

CR2032 battery. Cheap and plentiful. Lots of runtime for the amplifier.

Terminal block for the sensor.

Two banana plugs (not modeled) for the multimeter connection on standard 0.75" headers.

On/off switch (not modeled)

Sign me up.

[Webmanny]

Why not make your life simpler and get their USB version? No need for meters or calculations. Just plug it to your laptop or Windows tables and wait for the software to show you where you are.

http://www.bulkreefsupply.com/usb-sm...szOBoCHgfw_wcB

[theatrus]

Originally Posted by Webmanny

Why not make your life simpler and get their USB version? No need for meters or calculations. Just plug it to your laptop or Windows tables and wait for the software to show you where you are.



http://www.bulkreefsupply.com/usb-sm...szOBoCHgfw_wcB

It's not the new SQ-500 sensor which corrects for blue (and red) LEDs.

[theatrus]

Of course nothing precludes strapping a Bluetooth frontend to this if a phone interface is more appealing. When working in a wet environment where I may drop things at any time, I tend to prefer a ruggedized multimeter type system.

[oreo57]

Originally Posted by theatrus

Of course nothing precludes strapping a Bluetooth frontend to this if a phone interface is more appealing. When working in a wet environment where I may drop things at any time, I tend to prefer a ruggedized multimeter type system.

STOP it.. now you have me dreaming of a wireless PAR sensor, w/ autologging...
small flashing LED on board that tells you when data was sent....

[dread240]

So i'm looking at this chart... and it seems that it weighs 375-450 more (uv range) and puts less emphasis up around 650nm?

am I reading that right?. Super curious as to the data we may find with this sensor in regards to LED and halide and T5 dramamamamas

[oreo57]

Originally Posted by oreo57

STOP it.. now you have me dreaming of a wireless PAR sensor, w/ autologging...
small flashing LED on board that tells you when data was sent....

I suppose a built in altimeter is out of the question.. LOL

[dread240]

Originally Posted by oreo57

I suppose a built in altimeter is out of the question.. LOL

I'd like a tachometer personally

[gus6464]

Stop calling 400-430nm UV. It is not UV. It is just violet. Manufacturers need to stop it with that nonsense. There is no UV to be found on pretty much every mass produced aquarium LED light out there.

[dread240]

isn't 375-400 uv? Seems everything I can find online specifies those wavelengths as UVA

[gus6464]

Yes 390nm and below is UVA but it's kinda irrelevant since there are no LED fixtures out there that use these diodes. MH PAR will go up though as it has decent output in 390nm range.

At the end of the day though people who use 420nm actinic T5 bulbs will see their PAR number go way up since the old sensor was off by a boat load in this range.

[AZRippster]

This is a very good article to use as a reference in these types of discussions:

http://www.advancedaquarist.com/2014/5/aafeature

[dread240]

considering royal blues are the bulk of almost all fixtures there's a big step in that 450 range too.

[oreo57]

Originally Posted by gus6464

Yes 390nm and below is UVA but it's kinda irrelevant since there are no LED fixtures out there that use these diodes. MH PAR will go up though as it has decent output in 390nm range.

At the end of the day though people who use 420nm actinic T5 bulbs will see their PAR number go way up since the old sensor was off by a boat load in this range.

Par meters, by definition stop measuring at 400nm...so "numbers" won't go up.. (or are not supposed to).. though yes photosynthetically active photons do "exist" past that.. just hard to quantify..

funny how the new sensor will measure "blue" more accurately yet cut off more "UV"(sub 400nm)..

Arguably 405 or 410nm "violets" have a UV component..

The Radion Pro's have 4 405nm leds, and 4 415nm leds.

Buildmyled.com has 400nm "UV" LEDs. (discontinued)

BUT.. I TOTALLY agree on the absolutely poor use of "UV" and 400-ish nm LEDs.....
for reference:


Technically any light a Li-Cor measures on a sub 400nm LED is NOT uv either..
just measures what dribbles into the "purple" range, w/ some wash..

well I guess it is a matter of definition...
In which case you are absolutely right..

On the visible spectrum of light, violet light is at the end, with the lowest wavelength of 380-450 nanometers[4] (in experiments under special conditions, people have so far seen to 310 nm).[5][6][7] Light with a shorter wavelength than violet but longer than X-rays and gamma rays is called ultraviolet.

My bad..always cut UV at 400nm..

[dread240]

my reefll pucks have 400's in them too that show output in the 385 or so range as well