Guaranteed inaccuracy! No fun

Hi I have purchased this product and of course aufem directly schützenfest tested it came so implausible results this rumm I sent the item back and the money could have recovered.
For example, I have 10 drinking beer after waiting 20 minutes and had to blow 0.000% for another time I had then suddenly 0.3000% blown right out again and get 0.0000%.
I can not recommend this device I dunno where the good review come or whether I have simply received a defective production ka. I buy these products but a second time.