EC150 – Conductivity/TDS/Temperature Meter

I do monthly stream water quality monitoring using a very expensive YSI DSS Pro probe system. A county agency maintains and calibrates it. But in the winter I like to do more frequent monitoring of conductivity so I can track excessive use of road salt. I have been using an EC100, but needed a second for a friend. The EC150 adds total dissolved solids to basic conductivity. I do not use TDS but the EC150 tends to be easier to find on Amazon, and I just leave it set on conductivity. There are cheaper conductivity meters, around $10. They are pure junk. These Extech ECs have proper temperature compensation and are very linear. Their readings match those of the expensive YSI probe within a couple of microSiemens, and they hold calibration quite well (as long as the batteries are good). I check calibration each time I take them out, using 1000 microSiemen calibration fluid. The only time I've had bad readings was when the EC100's batteries were weak.