Review on 🔬 FORENSICS O2 Detector: NIST Calibration & Certificate, Dust & Explosion Proof, USB Rechargeable, Sound/Light/Vibration Alarms, 0-30% Oxygen by Andy Tran

Unit looks good overall but the calibration (calibrated late April 2019, purchased mid-May 2019) was very different by a few %. This is frustrating for one of two reasons: either a) the calibration performed by the company was not performed correctly (or not performed at all) and therefore the calibration certificate is incorrect, or b) the calibration has been greatly delayed in less than a month, which means , that most likely the block is defective. But I don't know which one. So I will return it.