Backyard Aquaponics
A place to discuss aquaponics

I'm not sure about this but I think it's one of two things -

1. Water and the ions it contains, conduct electricity more easily at some temps than others so you have to compensate for this or you'd get a false reading.

2. Electrodes (being imperfect) don't read accurately over the entire range necessary but they are consistent in how far off they are at any given temperature so you can compensate for it.

If the meter says it is automatic temperature compensated then it's measuring the temp as well as the DO, then it's adjusting based on the temperature to give you the corrected (true) DO reading. These are just guesses after doing a bit of reading so take them as such.

Hi Johny.

How's the system going?

Do you have the DO sensor in constantly? Or take it in and out?

Looks fantastic BTW

Thanks Columnmn.

It is going well. The DO probe is submerged 24*7 and I only take it to calibrate every few months.

Though having said that I have just picked up some new fish pellets but did not realize that they are sinking pellets. A real pain as the SOL gets them is they hit the bottom at all.

So a more controlled feeding is now required.

Do the results change much after each calibration? I'm just curious if the bio-film muddles up the results.

Which DO sensor did you end up getting?

Sorry Columnmn busy day. I will check on the weekend to see how it goes.

Columnmn the DO test.

Atlas Scientific DO probe & DO circuit board.
Running over 4 months now fully immersed in the trout tank 24 * 7.
DO before recalibrating : 9.03
After recalibration : 9.78

The interesting thing is that immediately after recalibration the reading was 4.89 and it took quite some time to come back up again.

The probe is sent a DO request every 5 minutes and is given the tank temp at the time of the request.

Does the DO vary during the day much? Or just a constant number?

Where did you get it from?

Thanks for the info BTW

The DO will vary by about 1.5 - 2.0 during a 24 hr period. Unless it suddenly gets really hot then it will show a larger swing.

The DO probe is from Atlas Scientific http://www.atlas-scientific.com. I have just purchased the PH probe and Multi Circuit UART Carrier Board. The board will allow 4 probes and control boards to be connected via one serial interface.

It works very well.

The prices of the PH sensors are coming down. I'm quite tempted...

But I should buy both if the postage is that much.

*ponders*

I know nothing about DO probes, but during my training the lead guy said that the probe has to be kept moving a bit to get an accurate reading. He just bobbed it up and down a few inches.

Anyone know anything about that? :raisedeyebrow:

Wow! I can not believe that I haven't at least commented on this thread so I can watch it every time there is an update! Maybe you can bring DO testing to the masses!

Could you say what units the DO readings are?

Gene the DO probe reads in mg/L straight of the probe.



Yes you need to keep water movement going past the probe. I have quite a bit of rotational water movement going past the static probe.

Once I get the PH probe I will have to pull down the the current setup for updating and will put up some photo and specs. They are quite easy to implement with just a call on the serial interface.

You've ordered the PH probe too?

Awesome, I'll let you be the guinea pig to see how well it works

Have you thought about hooking it up to the web like xively? It'll log and graph it all for you. All the libraries are there and easy enough to use also.

Columnmn you can call me paranoid if you like but I dislike sending data to third parties that includes any form of the Cloud.

All the data is stored on my server locally and can be viewed via an small program but I should get on with producing a web interface over Easter so I can see if things are working remotely.

Might a well start now.