ph electrode wont calibrate

[my03]

hey guys i have the tunze ph meter with co2 controller but can someone tell me why when i calibrate thr 7.00 solution it wont go beyond 6.00.

i have diped the elctrode in 7.00 calibration fluid for a week and the ph will calibrate to 6.5 now,

im assuming the probe is gone, is there any way to fix it?

thanks

 

[rvitko]

Have you calibrated the high end? Are you sure the electrode is clean and the solutions are uncontaminated, ideally new. In general when they are bad they are much further off than this. I would calibrate the 9 and then do 7 again and use a fresh solution- dipping in RO water and wiping down with a soft towel between solutions.

 

[my03]

thanks roger, im not sure what you mean by 9 and 7, because on my controller they only provide the 5 and 7 solution, the problem is the 7 solution dail wont go beyond 6.5

sorry to be stupid but what do you mean by the high end?

 

[rvitko]

5 and 7 are used if you have a plant tank or are measuring effluent, if you are measuring a marine aquarium use 9 and 7. I think they usually come with 5 and 7 as the most common uses are calcium reactor effluent and CO2 injection. It won't be as accurate but it should calibrate the same, do the 5, thenn the 7 and back and forth until you get it. In general a bad electrode gives a reading like 3 or 11 in the 7 solution.

 

[my03]

hi roger, sorry to bother you again, but i have just realised that the ph9 dail is actually the 5 dail as well, this is not the calibration tuner i am having trouble with, though it is reading quite on the low side (same as the ph7 that i am having trouble with) this sugest the probe is gone doesnt it? is there any way i can rehydrate the probe? i have notiuced the tip of it is dry, its not a smooth glass like the other parts of the probe, is there any way to reverse this?

thanks

 

[my03]

sorry mate one more question is does the tunze controller need to be replaced by the tunze elctrode? 0or can they be replaced by any electrodes? what is the difference between glass and plastic? and where is a cheap source of replacement electrodes that will ship[ to australia? they cost about 150 + USD so i may want to get them from the states.

thanks

 

[rvitko]

They are about $120 for the glass electrodes here. You can use any electrode but I really don't think your electrode is gone.

I will tell you how to recharge the electrode by PM but I waive all liability, it is a fragile operation and best left to someone who has experience. In my experience bad electrodes are way off. You can quatitatively test the electrode quality with a volt meter, the reading from the tip to the shell of the BNC should be 100mV, at about 80mV they don't work.