pH and Conductivity/Temperature Probes require maintenance at least once a month to maintain accuracy and reading response speed. Everything you need to clean and test your Conductivity (ppm/EC)/Temperature Probe Manual2x 20ml Disposable Bluelab 2.77 ec Conductivity Standard SolutionPlastic BeakerBluelab Conductivity Probe CleanerBluelab Conductivity Instrument Cleaning Kit) The instrument is only as accurate as the probe is clean. Accurate readings simplify crop management and provide improved growth. Proper ppm/EC probe maintenance also ensures that you maximize the life of the probe and instrument. The probe surface is where the instrument takes its reading of the solution. If the probe surface is dirty or contaminated, the readings may be inaccurate. Much like the windshield of a car, if it is dirty, you can't see it! If the probe surface is dirty, it can't read the solution.