Product review (1 stars): Not what is shown in the image
I just received this unit and within seconds after opening it, I am returning it. The main reason I went with the unit is because it showed a location on the back for calibration. In the advertisement the back panel even reads calibrate with NaCI and had a spot for making adjustments. However when I received my unit it had no marking on the back and no adjustment screw inside the adjustment hole. The unit probably works fine but from what I read over time the lower end models all need adjusting to ensure they read accurately and I want a unit I can adjust. For a few dollars more I am going with a HM which not only shows the image of a model that can be calibrated but also mention it in the description as well.