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76 <br />• :>. Cold weather (below 15°C) causes malfunctioning of <br />the meter. <br />4. Wind causes malfunctioning of the meter. <br />5. Static electricity build up on the dial face <br />causes malfunction of the meter. <br />We have established a policy that a pH meter has to be <br />placed in as controlled an environment as possible, even <br />when it is taken in the field. Consequently, it is left in <br />a warm portion of the vehicle. and samples are taken to the <br />meter for pH measurements. Only on calm, warm days do we <br />risk taking the pH meter to the water. For most water, the <br />pH measurement will not change for a half-hour. So if you <br />can. return to--the lab within that time, field--pH measurements- <br />are unnecessary. <br />Even in a controlled environment, a pH measurement is <br />not easy. The principal culprit is the glass electrode which <br />is easily fouled. Consider the glass electrode a necessary <br />evil; most water chemists would not bother with such a tem- <br />peramental apparatus if the measurement of pH weren't important. <br />The following pieces of advice should be considered: <br />1. Always have on hand 3 standard buffers of pH 4.00, <br />7.00 and 9 or 10. In some instances a faulty system will <br />be adequate over 3 pH units to solve problems. <br />2. Never trust the battery check indicator; if there <br />is a question, check the batteries themselves. Most portable <br />pH meters require a mercury cell as a constant voltage source. <br />These batteries tend to fail abruptly and often show failure <br />E