MARTYN F. CHILLMAID / SCIENCE PHOTO LIBRARY MARTYN F. CHILLMAID / SCIENCE PHOTO LIBRARY
Measuring pH levels. Hand holding a pH sensor in a beaker of acid while connected to a datalogger through a wire (upper right). Here, the sensor will measure a low pH (between 0 and 7), which indicates that an acid is present. The pH reading is recorded by the datalogger, and the variation in pH over time can be plotted.
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