My beloved ordered a BP & Pulse monitor last week as he likes to check his pulse before he takes his medication.
It arrived today so he unpacked it immediately, he fitted some batteries and put it on his finger.
'It's not working' he said 'what a waste of money, it's not working I'm going to send it back' he ranted, ripping the offending article off his finger.
I intervened 'It shows the speed of your pulse in beats per minute' I explained 'I suggest you put it back on your finger for at least 30 seconds to give it a chance to do some counting!'
He did, it works just fine.