Review on DIGITEN Digital Tachometer Proximity Mounting Test, Measure & Inspect by Christopher Clearfield

The seller claims that this tachometer has a detection distance of 10mm, but when I received the part the specs said 2-3mm. The seller called me back and said although he says 2-3mm it will work at 10mm. At the moment I did not refute because I had not tried it at that time, waiting for the arrival of the 12V DC 300mA converter. Got the voltage converter today and went to the store to hopefully see what it recognizes at 10mm. At this point I still don't know how the part is faulty!