The ESSENTIALS pH Meter is truly the most rugged glass type pH tester around. It is water and drop resistant. Even if the tester is accidentally dropped into the water, it will remain afloat. This means you are able to retrieve the meter immediately without damaging the electronics. It is easy-to-use as you can just dip the sensor into the test solution - stir and wait. This unit will deliver a stable reading in about 20 seconds. The meter has a minimum lifespan of about 1 to 3 years depending on the rate of sampling. The energy saving feature shuts off the tester when it is not in use. The unit also displays a low battery symbol to warn you before it degrades the accuracy of important readings. It has digital calibration at the push of a button and a lit screen for when under dark foliage.