Supakorn Surakulananta juli 25, 2018 To whom it may concern, I have a Vaisala 2 items, HMT120/130, M170. It's time to calibrate this instrument. I'm not Metrologist and not expert in a calibration. I'm a beginner in this. Please let me know how to set the maximum permissible error (MPE) of an instrument. I'm not sure it may be called "Tolerance of an instrument". Reply