Pro Mariner Corrosion Meter
 

Picked up a Corrosion Test Meter (analogue) and manual at a Boat
jumble over the weekend and it seems to be OK. It seems to work OK
testing my steel hull - there was no change when AC shore power was
switched on/off and disconnected - which is reassuring - but what
readings should I get on a steel hull, painted with magnesium anodes
in fresh water.
On my hull I got 390mv and a neighbours hull 440mv.
I would also like to check all is well with the meter - I put both the
Ag electrode and neg into a glass of fresh water and the meter
stabilised at 150mv.

I know the PM do a digital meter version which is better for fresh
water - but what is the difference in the digital meter they sell and
any other digital meter??

Any tips would be appreciated - the manual is OK but could be better.

TVMIA