What you have there is an EC meter,used to measure ppm(nutrient levels)in resevoirs or DWC buckets,not a ph meter,CF (conductive Factor)tells you when the the levels are proper, low or high,when to add,most nutrient manufactures have a reccomended level for different growth phases,nice piece of equipment,learn to use it,I dont condone stealing,but if your concience allows,maybe after a successful grow or two you can donate one back to the school (anonymously of course )just consider it a temporary loan,just my patriarchal instincts kicking in(Ward Cleaver)....bonbon