Problems w/ pH meter

Hey there again rollitupers...

I've been using a meter based ph/light/moisture multimeter I got from lowes for around $5 for the last month or two. It's pretty unreliable, so I got a new digital pH meter recently. My new digital pH meter is also pretty eratic. I have to recalibrate it several times during usage and it's very inconsistent.

For instance, I mixed some nutes in to 7.0 distilled reverse osmosis water that had a ppm of 002 tds. I took a pH reading after adding nutes and got 4.5ish, so I added some pH up and got a 5.3 reading. I added more pH up and got 5.1, added even more pH up and got 4.6. I recallibrated several times and am consisntly getting irrational pH readings. Can someone recommend me a make and model of a reliable pH meter I could get and/or help me with this one I currently have?

how r u calibrating?
is ur battery good?

The entire unit is brand new, including the battery. I'm callibrating with 7.01pH millwauke buffer solution. I put the electrode in the package and use a knife to twist the small screw on the top until the reading is 7.01.

Believe it or not, the battery-free meter does work. Get some 5% vinegar and toss the probe in there. You should get a reading of 2.4 (or in the case of that meter, it should peg out at 3.5) after you've done that, wipe the probes off and put it in straight tap water. You should get a slightly below 7 pH (not taking into account if any sort of salts are in your lines or in your municipal water supply, just chlorine and fluoride)

I certainly have no problems with my analog meter, it just needs time to register lower pH levels because it's working by metal-ion difference to measure the pH

make sure u mix very well b4 taking a reading ....even waiting a while after ph'ing ...i found mine would change overnight...sometimes not having to ph up or not as much.
I notice if the water is moving i will sometimes get slightly different reading when settled.

Noted. I eventually got it to read about 6.1 but it took a RIDICULOUS amount of pH up, which seemed to me it might be overkill. Also my plants are beginning to sex and I'm pretty confident one of them is a male and the others all female. Since I have to kill the male off anyway, I doused it heavily in the supposed 6.1pH water, we'll see tomorrow how it does. Hehehe.

b4 i had calibrating solution i confirmed my ph ..somewhat, with my aquarium drops ph tester....which is what i originally used and worked well

Well, my question would be are you growing in soil? pH changes in soil take awhile to occur after adding anything.

i'm growing in soil, but i ph my water after adding nutes to get a @ 6.5 runoff from the soil.
Sometimes it seems the ph up takes bit of time to fully adjust the water for good reading...if ur mixing a lot.

Checking your runoff pH doesn't give you a very accurate reading of the soil. Check the soil after an hour of doing anything and let the meter sit in the soil for at least two minutes for an accurate reading. After all, it's the soil you're trying to check, not the runoff.

dont thimk these meters work in soil do they ?

Yes, they do and they work fine as long as you have the probe in moist soil over the copper and aluminum probe sleeves.

Right I'm talking about measuring water/nutes that I'm about to add ot the soil, though.

You should ph your water before and after nute addition - give the nutes about 15 minutes for full dissolving and pH adjustment, pH it, your soil, water your soil, check the pH an hour later.

To calibrate the analog probes, you simply polish the probe length with a highly-acidic (lower than 3) liquid, like vinegar, while it's set on the pH setting. If it's the copper and aluminum two-probe design, make sure both probes are being wiped at the same time with the same cloth soaked in your acidic solution.