The Mark IV E-Meter is just sensitive enough at sensitivity 16 to get a pc’s rudiments in so the pc knows it and to check out a goal.
No earlier British or American meter is this sensitive.
The use of a meter which does not so register will not detect out rudiments and will not find a goal.
A pc audited on a meter even slightly less sensitive than this will have answers to rudiments questions although the meter says they are clean. Therefore the pc is nerved up with missed withholds and you get an ARC breaky or unsatisfactory session.
This is the most fruitful source of “dissatisfied” or “difficult” pcs. They are being audited with rudiments out when an insensitive meter indicates the rudiments “clean”.
The needle gets dirtier. It becomes hard to read the meter. And, due to lack of sensitivity alone, the meter will find no goals. And as the needle is wilder, goals are even less likely.
Model Session and havingness sessions which are properly run by the auditor will result in an even, clean needle. But if the meter is bad, even when auditing is good, the needle will get wilder as the ruds are actually out even when they seem to be in.
You are doing earlier auditing and Prepchecking to clean up the wildness of a needle so Routine 3GA can be run. If auditing is good and the needle is getting worse, there’s something wrong with the meter or the operator’s meter reading.
Only the Mark IV shows if a rudiment is clean. All others ruin sessions and needles and give you ARC breaky pcs.