Is my Hanna PH/EC combo pen shot? Frustrated!

[TwinTurboGuy]

Hey all,

I have a Hanna PH/EC combo pen part # HI98129. My plants started to show some lockout and twisty leaves because of PH issues.

I only had it for about a year and its giving me a hard time. I noticed a problem with the PH readings I let it self calibrate in 7.01 calibration solution, and it read 7.6-7.7. The PPM readings were way off as well. I tried to calibrate it in 1500ppm calibration solution and it read around 750ppm. Then I tried to adjust it with the 900ppm solution and it read between 600-650ppm.

I figured that the PH electrode was done for so I ended buying a replacement probe since that is more important as I can easily dilute nutes by measuring the amount of water. After I added the electrode, I tried adjusting it again with 7.01 solution then it read out to 7.27 after a few hours.

Is this reading close enough or is my pen shot? Anyone have experience with these? I grow in coco and I keep my PH between 5.8-6.0 (according to my pen). But for some reason, it seems to be showing symptoms of PH problems.

Any takers?

 

[Strawberrycough]

sounds like the PH meter is shot. PH pens like to stay we and PPM dry ... so next time get 2 separate pens.

 

[FreezerBoy]

My homework suggested that pH pens are a crapshoot at best. Milwaukee sucked least, followed by Oakton with Hanna bringing up the rear. I stuck with the $5 test kit from the aquarium store. I spent my money on a Bluelab EC truncheon. 5 year warranty, no calibration, extraordinarily low maintenance (wash the tip once a month)

Have you kept a journal? That would tell you what 0.1 ml of pH down does to a gallon of nutes and you can extrapolate from there.

 

[petemoss]

Good advice, FB! I had a Hanna Grochek continuous PH/TDS meter and the PH probe dried out after a year. The hydro store guy told me that the PH probes often go bad after about 6 months! They wanted $70 for a replacement probe with a 6 month warantee. I said "no thanks" and bought a $5 cheapo PH tester and have been using that for over a year. I'm pissed that I wasted so much money on the Grochek. With all the calibration solutions and storage solutions and cleaning solutions, they got me for over $200. Never again!

 

[ItsGrowTime]

The ph electrode is dead after about a year. I had to replace my electrode right at one year on the dot. Just replace the ph electrode and youll be back in business. $40 or so online.

 

[T.Baggins]

the calibration of any pH meter is dependent on the quality of the pH buffer being used. the pH calibration process is done to standardize the changes to the glass electrode to a known reference. for instance a pH electrode at 25*c theoretically generates 0 mV in a pH 7.01 buffer and + 177.48 mV in a pH 4.01 buffer.the tolerances for new probes are +/- 10 mV in a ph 7.01 and have a range difference from +168.6 to 186.35 mV(95-105% slope) in the voltages generated in 7 and 4 buffer. the calibration of the pH probe is done to standardize the meter by telling it what voltage, which changes over time, is being generated in a solution with a known pH value.

what impacts the voltage that a pH probe will generate in a pH buffer? there are a variety of influences on the voltage potential will be from a pH electrode. these include the specific characteristic, at that moment in time, of the electrode and the potential for errors during the calibration process. here are some influences on the probe potential:

1) hydration layer of the glass sensing portion. an electrode that is dry will generate a different voltage in pH 7.01 buffer than the same electrode that has been allowed to hydrate in a solution for a couple of hours. all glass electrodes should be stored wet in a solution to maintain the hydration layer. the ideal is to use an electrode storage solution. if you choose not to use then a pH 4.01 or 7.01 buffer should be used. never store a pH probe in purified (r.o., distilled or ion exchange) water. it will cause it to enter by osmosis.

2) build up on the glass sensing portion. an electrode that is clean will generate a different voltage in a pH 7.01 buffer than the same electrode with a build up on the glass bulb. a dirty electrode could be disastrous if a precision measurement is needed.

3) a physical change to the buffer. the calibration of the pH electrode is only as good as the buffer being used. lets say that a pH probe generates a 0mV in a fresh pH 7.01 buffer. the meter is calibrated daily using a beaker that has pH 7.01 buffer. if after a few days the voltage of the same electrode is recorded and is found to be generating +25 mV, it could be possible that the voltage changed due to the electrode being dirty, or it could be that the pH 7.01 buffer is no longer 7.01. if the probe is still working but is generating +25 mV due to a contaminated buffer then the error in measurement is going to be about a 1/2 pH unit off.... good lock

 

[hazey4]

My homework suggested that pH pens are a crapshoot at best. Milwaukee sucked least, followed by Oakton with Hanna bringing up the rear. I stuck with the $5 test kit from the aquarium store. I spent my money on a Bluelab EC truncheon. 5 year warranty, no calibration, extraordinarily low maintenance (wash the tip once a month)

Have you kept a journal? That would tell you what 0.1 ml of pH down does to a gallon of nutes and you can extrapolate from there.

I just bought a bluelab ec truncheon and was wondering which of the ppm readings I should use the 500X or 700X?

 

[FreezerBoy]

Neither. PPM, TDS and CF are all EC readings converted to nonsense.

You have the real thing. You have an accurate EC reading. There's no need to convert it to nonsense unless speaking to someone unlucky enough to have your level of equipment. Note that there are other nonsense conversions as well, including but not limited to: x640, x650, x768. If I had to guess, I'd say x500 is the most common

Stick to EC.

 

[hazey4]

Thanks was just wondering since other people usually talk in terms of ppm rather than EC.

 

[pezoholic]

EC is the way to hands down, unless you can get a cF meter LOL which is big $$$

Calibrate/check PH AT LEAST ONCE A MONTH
TDS/EC/PPM AT LEAST EVERY 3 MONTHS

Also PLEASE DO A dual point calibration...aka 4.01 and 7.01.....gives the meter a way to check itself. Make sure to keep BOTH OF THE PROBES nice and clean, keeping them stored in either the storage solution or 4.01

Proper maintenance is key and those who cant get them to last more than 6 months are doing something wrong/not taking care of there investment. Also whatever hydroshop you went to is weak, I can R/A just about anything with the hanna name on it!

btw I own the 129 as well.

 

[badugi]

Never again will I use pH pens. Only time one really came in handy was when I was trying to calibrate my eyes to which GH liquid pH tester color meant roughly which pH.

 

[FreezerBoy]

EC is the way to hands down, unless you can get a cF meter LOL which is big $$$

He's already got one built in to the Truncheon. CF is ECx10. The least offensive of the conversions, it's still a conversion.

Truncheons require no calibration. Far as I know they can't be. The electrode pads do need to be cleaned occasionally. 2-3 drops of soft scrub bleach once a month.