I purchased this voltmeter on Amazon to the charge state of my car battery to check. The unit came after 1.5 weeks delivery time for me to well packaged. I have checked the voltmeter is equal and it is working properly. A comparison with a calibrated professional unit (price almost 1300 euros) showed a deviation of + 0.2 volts. This deviation was linear and is completely at this price okay. One can just expect a professional unit at this price, but to check the charging voltage of Alternator absolutely useless.