Designed for low cost monitoring of water conductivity. Includes 2 probes to allow for measurement in 2 places in your system, Typically you would have one probe on the feed water and one probe on the product water to show you the amount you are reducing ionic contamination in your water system. Measure 1-1000 p.p.m. with the push of a button. These economy meters are excellent for determining the condition of your Reverse Osmosis Membrane.