pH Meter ADWA Says -2.0 When I Calibrate! Need Help ASAP!

[xxxskunkxxx]

Thanks for helping me out!

I was taking readings from my dwc bubblers and it was working great, then I got to the last bubbler and when I dipped it in the water it started displaying -2.0 with the little pH sign next to it.

Its ridicoulus to think my nutrient solution is -2.0 ph when the plant is perfectly healthy.

So I tried to calibrate it and I followed the normal procedure (this works been doing it for the last 6 months):

1. Turn on and dip in 7 ph calibration solution press "Cal", wait till stablized and then press "Cal" again
2. Its supposed to ask for 4 ph calibration solution now but it just says "-2.0 pH", where the fuck do I get -2 ph calibration solution?!?
IF it did work normally I would continue like this:
3. Rinse with distilled water.
4. Dip in 4 ph calibration solution and press "Cal", wait till stablized.
5. Turn off and rinse with distilled water, ready to use.

Its an Adwa "AD-100" pH meter, the distributor website says it measures from -2ph to 14ph.

Is "-2.0 ph" some error message?

Been googling for 2 days and cant find any help. Please lend a hand, my plants need 5.5 ph water!

 

[MASHUP]

How old is the meter? Have you always maintained moisture for the probe's tip? The tip may not dry out, this effects performance and accuracy. Left dry too long and kiss it goodbye.

Sadly, I've been through countless meters over the years and you come to accept them for what they are. Temporary.

Best results have been with a HANNA all in one, just replacing the probe when need be.

 

[MASHUP]

Also, a little eye opener since you seem to be stressing over the PH to the .1 increment.

Plants are plants. There's a fairly wide window of PH for access to certain minerals. Use these numbers from companies as a guide to where you should be. I personally (along with everyone I know in DWC) will mix up my nutes and not adjust the PH.

The PH will rise naturally. When it gets close to 6.5, sometimes even 7 I will then adjust. This assures your plants have had access to all of the needed minerals. If you force 5.5 24/7, how do they access the nutrients slightly above and below?

Ultimately let the plants tell you what they need. We both know that PH isn't 2.0, but you said the plant is healthy. Don't fix what isn't broke.

 

[xxxskunkxxx]

After every session I always spray the probe and bottom of the meter with ph 7 water and rinse the cap, so it has never dried out.

The meter is 6 months old.

Once ive mixed up my solution in the big reservoir the ph is at 9 or so because of Rhizotonic (very alkaline stuff), so I always make sure the ph is 5.5 before I give it to the plants.

Of course the ph rises naturally and I adjust it every 24 hours, it goes from 5.5 up to 5.9 - 6.2 so the plants are getting access to all they want, they are very healthy and have lush growth so don't worry about them Worry about the ph meter!

 

[MASHUP]

Given all of that. It seems like your probe/meter may have failed on you. Only step before trying to replace it would be to give it a 30min bath in a probe specific cleaning solution to help break down any residues potentially interfering with its operation.

Best of luck, stay green.