Review on Highly Accurate and Reliable 3-in-1 Professional Water Test Meter: TDS, EC, and Temperature. Complete with Protective Leather Case. by Leroy Jacobs

You can calibrate this meter but you must cut the bezel to the left of the "Shift" button. I used a precision knife and then twisted the handle. Not too much on arrival. This does NOT come with calibration fluid. I've seen one star reviews for this reason alone; It's a standalone counter and it does what it's supposed to do. Ideal for checking water quality and/or nutrient levels. If you want the calibration button on the outside of the meter make sure you buy the newer version 2.