trusting the Dano plus parameter readings?

[Ballyhoo]

I have Red Sea 90 watt LED . This dano plus par meter placed directly beneath the LED and barely submerged under any water basically at the surface reads 444. the par meter rapidly drops and you see at the rock it reads about 80 par. Is it possible that the power is that strong at the surface

down towards the bottom at the rock it's 100 par.

 

[JonoH]

I have one of these, and I measured the same as I had previously with an Apogee - however I have not been able to do a side by side comparison yet.

 

[Ballyhoo]

I have one of these, and I measured the same as I had previously with an Apogee - however I have not been able to do a side by side comparison yet.

boy you believe it to be roughly accurate?

 

[JonoH]

boy you believe it to be roughly accurate?

Yes, its within 10%

 

[Tk161900]

I work in metrology at an aerospace lab and was able to get this meter on a rail and get it calibrated. It was surprisingly within tolerance. I have the results, but it was basically within 0.2% of reading.

 

[Ballyhoo]

thank you for your results. Did you just follow the basic calibration procedure?

 

[Tk161900]

thank you for your results. Did you just follow the basic calibration procedure?

I work in the Physical lab. I don't have much experience with optical items so another tech helped me get this done. We weren't able to test the whole range at the time, but tested enough points to get a line fit on the data and due to its small non-linearity I feel comfortable extrapolating beyond the calibrated range.

The standard we used is a calibrated bulb at 5500K that at 6.9 amps provides an output which at certain calibrated distances equates to a value in foot candle units. The light meter was mounted on a calibrated rail to ensure the proper distance from the bulb was applied. I found a simple conversion from foot candles to par and used that. We could have tested higher, but didn't want to tie up working equipment for too long. 100 par was good enough for me and as stated before I have confidence in my unit to remain linear beyond 100 par. This calibration beats standing outside at noon with your light meter any day of the week...

Here is the data I took.

TI	STD
Par (mmol)	Calculated PAR
2.4	2
5	4
8.8	7
17.6	14
25.2	20
50.6	40
75.5	60
100.6	80
114.7	91.2
125.4	100

I used these values to generate a slope and intercept.

Slope	0.795914548​
Intercept	-0.029186939​

This can be applied to my unit to correct for the discrepancies(PAR Reading x Slope + Intercept). The worst error for the calculated outputs was 0.244% of reading at 40 par. I think that's pretty good for the price of this meter and decent enough for checking basic light levels like I am.

 

[oreo54]

I work in the Physical lab. I don't have much experience with optical items so another tech helped me get this done. We weren't able to test the whole range at the time, but tested enough points to get a line fit on the data and due to its small non-linearity I feel comfortable extrapolating beyond the calibrated range.

The standard we used is a calibrated bulb at 5500K that at 6.9 amps provides an output which at certain calibrated distances equates to a value in foot candle units. The light meter was mounted on a calibrated rail to ensure the proper distance from the bulb was applied. I found a simple conversion from foot candles to par and used that. We could have tested higher, but didn't want to tie up working equipment for too long. 100 par was good enough for me and as stated before I have confidence in my unit to remain linear beyond 100 par. This calibration beats standing outside at noon with your light meter any day of the week...

Here is the data I took.

TI	STD
Par (mmol)	Calculated PAR
2.4	2
5	4
8.8	7
17.6	14
25.2	20
50.6	40
75.5	60
100.6	80
114.7	91.2
125.4	100

I used these values to generate a slope and intercept.

Slope	0.795914548​
Intercept	-0.029186939​

This can be applied to my unit to correct for the discrepancies(PAR Reading x Slope + Intercept). The worst error for the calculated outputs was 0.244% of reading at 40 par. I think that's pretty good for the price of this meter and decent enough for checking basic light levels like I am.

Thanks for the work. So from the above data the basic finding is any measurement from the Danoplus can be corrected to "actual" ( calibrated standard 5500k bulb)
by multiplying by approx. .80
2.4 x .8 = 1.92 ( close enough).
And it's consistent to at least 100 par.
Well for hobbyist uses that's great


But if one does a search about actual comparisons to say the defacto standard Apogee most correction factors are greater than 1 not less. And some as high as 1.4 ,1.6. ect.

This is a bit disconcerting. Now my " thesis" here is these are going back to the old poor blue sensitivity of the orig. Apogee.
But that meter is still $379 and the Danoplus ( or unlabelled unit at AliExpress is on an " anniversary" sale for $118- ish) is like $150.

As a freshwater guy seems useable " as is" or even in horticulture.
But there is the problem ( not for here) of the horrible red response as well IF the sensor designs are similar. Also currently ? since there is no sensor spectrum response graph.


As usual, your data actually creates more questions than answers..Par for the course ( pun intended).

Hmm..