Man, it's strange but I ran a Bluelab truncheon for 7 or 8 years with no problems at all. Finally had to replace it, and now I've gone through 3 replacements for it, through warranty, because all of them began giving false readings in short order. Seems to me they aren't as bulletproof as they once were. That, or my luck is truly terrible.Just tested a bluelab truncheon. You might think why? with an auto-calibration meter. However, it missed by a third.
1g of table salt, in 1 liter of water, is 1000ppm on the 500 scale.
Or my meter was right, and it's me that's broken