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Portable pH Meters

pH Meter Maintenance Recommendations

1. Calibration Frequency: Probably one of the most frequent questions we get asked - and there isn't an easy answer we can give. With use pH electrodes drift and as a result you will need to recalibrate your pH meter to the electrodes new characteristics. By and large it depends how accurate you need your pH results to be as to how frequently you calibrate - if you need 0.01pH accuracy then you'll be calibrating every day, if on the other hand you are only interested in 0.1 of a pH or even less, then you need not calibrate that often.

2. Calibration Procedure: Place the instrument into calibration mode either by pressing the CAL button or pressing and holding down the ON/OFF button until CAL appears on the screen. At this point most meters will request the use of Buffer 7.01, and all meters will need to be calibrated to pH 7 buffer first. Place the electrode in to the buffer 7 solution so that the bottom inch of the electrode is submersed. Hanna meters are programmed to automatically recognise a selection of Buffers (please check the product specific specifications to find out which solutions). While the meter is waiting for the reading to stabilise a clock symbol or hour glass symbol will flash (on some of the hand held meters the reading will flash). If the meter is unable to recognise the Buffer the message WRONG will appear on the screen. Once the meter has reached a stable reading it will automatically calibrate itself. The meter will then request the use of the next buffer solution, the screen will now show ‘USE 4.01’. At this point remove the electrode from the Buffer 7 solution and rinse it under tap water (or deionised water) and then place the electrode into the Buffer 4 solution. Once again the meter will show that the reading is stabilising by either flashing oshowing an hour glass/ clock symbol.

3. Electrode Life: How long a pH electrode will last is dependant on a number of factors. How suitable the particular electrode is for the task in hand, how extreme the chemicals it is exposed to, frequency of measurement and care and maintenance of the electrode. Typically, a general purpose electrode being used to measure pH of water could be expected to give between 1-2 year life, although we have known electrodes go on for many more years than that. An electrode continuously monitoring swimming pool water, on the other hand, might only last 18 months.  Even shorter electrode life can be experienced if the substance is particulary agressive, or if the temperature of the solution is particulary high. In both of these cases careful choice of an electrode designed specifically for that purpose will result in much longer electrode life.

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