This video shows how to calibrate an Elmeco pH-meter. Take the probe from the pH-meter. Rinse the probe in demineralized water and wipe it with a cloth or tissue. Turn on the pH-meter, adjust the buffer temperature with the left knob and wait 1 min. Then pour a little pH7 buffer liquid into a cup. Put the probe into the liquid and stir briefly You will now see that the pH-meter shows a value of around 7. Use the center knob to set the value to 7.00 exactly. Rinse the probe again in demineralized water and wipe it with a cloth or tissue. Then pour some of the pH4 buffer liquid in a different cup. Put the probe back into the liquid and wait 1 minute. Use the right knob to set the value to 4.00 exactly. Rinse the probe once again in demineralized water. Then fill the holder with some probe care and put the probe back into the holder.