Homemade Calibration Solutions: measures not as precise as thought

[dgasmd]

Actually, I do have a homemade ORP calibration solution with bleach and RO water. I'll have to find it first.

 

[Randy Holmes-Farley]

Yes, let us know. That's been suggested to me, but I didn't think it would be very constant. Sort of like calibrating a pH electrode in an acid solution (as opposed to a buffered solution).

 

[Skipper]

Ok, the disclaimer/addendum has been added to the article.

http://reefkeeping.com/issues/2004-06/rhf/index.php

 

[Randy Holmes-Farley]

Thanks, Skipper.

 

[dgasmd]

Randy:

I found it. I got it originally from the guys at PinPoint, which I see now they have their solution on the market as well. Don't ask me about accuracy because I don't know, but they claim it is extremely accurate.

1 part bleach : 5 parts RO/DI water

That should yield a 700 Mv reading.

 

[Randy Holmes-Farley]

OK, thanks. I'll look into it.

 

[Billybeau1]

I'm gonna try that tonight. I assume since you got this from pinpoint, then they are saying its ok for diluted bleach to get on your probe.

I'll report back tommorrow.

 

[Billybeau1]

Well here are the sorry test results

5 ml clorox bleach - 25 ml ro/di

Put probe in at 7:00pm
7:00pm - 480mv
7:15pm - 520mv
7:30pm - 555mv
7:45pm - 578mv
8:00pm - 602mv
8:15pm - 611mv
8:30pm - 619mv
8:45pm - 631mv
9:00pm - 640mv
9:15pm - 645mv
9:30pm - 652mv
9:45pm - 662mv

Went to bed

Left in overnight 6:00am - 777 mv

Draw your own conclusion

 

[Randy Holmes-Farley]

Thanks for the experiment. I assume the probe was calibrated somehow?

 

[Billybeau1]

No its a Red Sea. Cannot be calibrated. However even if it was off, I think its safe to say that the ORP probes just take too long to react to anything to make a good test.

I seem to recall you calibrated your probe in 400mv solution. How long did it take to stabailze ?

 

[Randy Holmes-Farley]

Within a few minutes it was close to 400 mV, and then over the next hour or so it rose from about 400 to 409 mV.

 

[Billybeau1]

Interesting. I put the probe back in the tank at 6:15 this morning (Central) and one hour later it is only down to 460 from 777. It is dropping very slowly.

 

[Randy Holmes-Farley]

Interesting. I put the probe back in the tank at 6:15 this morning (Central) and one hour later it is only down to 460 from 777. It is dropping very slowly.

Remember my comment here: :lol:

I hate ORP
http://reefcentral.com/forums/showthread.php?s=&threadid=799138

 

[Billybeau1]

Yeah I remember :lol: