A few basic rules for test equipment:
- Clean and inspect test leads after each use. If you spot a problem, don't try to fix it. Replacing suspect test leads costs less than labor time spent on repair attempts, and repair attempts are seldom effective.
- If someone steps on a test lead or rolls a cart over it, assume the insulation has been damaged. Replace the test lead.
- Always apply test leads one at a time to terminals rather than applying two leads simultaneously, as this prevents arcing between the leads.
- Know what environment you're measuring in. A DMM rated as CAT II isn't safe to use on a service panel.