What is conductivity?
Conductivity measures how well water carries an electric current, in microsiemens per centimetre (µS/cm). Because dissolved salts are what conduct, it is a fast proxy for how much dissolved solid a rinse tank holds — and therefore for whether parts will dry spot-free.
A handheld conductivity meter gives an instant answer where a full water analysis takes days. On a rinse line it is used as a control limit: when the final rinse rises above the set figure, dump and refill, or increase the fresh-water feed.
It is also the standard way to prove a DI plant is still working. Resin exhausts gradually, and the first symptom is usually a slow climb in rinse conductivity — visible on a meter weeks before it is visible as spots on parts.
The same measurement is used on cooling water, where rising conductivity indicates concentrating dissolved solids and signals that blowdown is insufficient.
