They say that a trimeter is only as effective as the probe is clean. Depending on your water source you should clean and calibrate your tri-meter every week as a minimum.
All of this information came with my tri-meter. Here is the probe, the probe "cleaning tool" and the cleaner. The probe goes into the end of the cleaning tool after you have put a small Amount of cleaner in it, give it a few twists, and then (Sorry I am not going to try and spray itr and take a picture at the same time thank you) rinse it off well, with fresh tap water. The cleaning solution can be used on the face of the ec probe as well, it doesn't take much, it does come out fast, may want to use a q-tip to dip a little out. I will next time.
So now we have a clean in accurate probe, and we need to fix or 'Calibrate' that. Sounds intelligent, after you do it a few times its not all that impressive. Here is the calibration kit I use, the little veils don't hold much, I think Earl estimated less than 50cents/ week.
First put your probe in the ph 7 solution. It reads 7.2, see told you its inaccurate now, we know the ph 7 solution is ph 7 (duh) so now we need to tell the meter that it is 7. SO..this is really intense now. we push and hold the buttonm that says ph calibrate until it flashes and clears the reading and then..... we push the button that says ph7, telling the trimeter, hey stupid this is ph 7. Now the next step goes the same way except for the solution we use, the buttons we push are the same either way. If your water tends to have a ph above 7 then you will want ph 10. Mine is below 7, I use ro, so I use ph 4. Same process either way. Put your probe in the ph 10 or 4, let the reading stabilize, see its wrong again. No stupid ph calibrate, flash. then ph4/ph 10 calibrate. Bang, ok you are right its really ph 4. now leave me alone for a while, put me back in that nice 'fresh' tap water til you need me again. VV