It is recommended that they should be calibrated every 6 months for theoretical "100% accuracy", however 100% is bullshit for these handhelds, so I compromise and get mine every year... though it's not that often I want (or have the need) to drive after a session and need to be tested...
I don't flip a coin when I'm near the 0.05 mark... c'mon, whatcha expect from,
If your first cut is too short... Take the second cut from the longer end... LBD
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