Power quality recorders and monitors - How is the unit constructed?
What can I expect ?
Some companies pay particular attention to design and make the unit servicable. Others, may decide to coat and encapsulate the electronics. While it may sound ok at first, please note that these units cost thousand of dollars and you are installing them at the very place where other electronics have had issues.
If you spend several thousands of dollars on a unit and then find that a unit needs to be serviced after two years, you probably want it repaired. Replacing a battery, mov, and fuse does is not regarded as a repair.
Ask if the circuit boards are encapsulated by any means. Other than some conformal coatings- if the main PC boards are encapulated and can't be replaced, and it fails, it's trash. Ask if the main boards can be replaced- if the answer is no, don't walk but run away. Potting, plastic dip, and RTV are some of the ways manufacturers cover up poor mechanical designs. They are the duck tape of the electronics world.
Ever here the expression, 10 lbs in a 5 lbs bucket? The smaller the unit, the more you should ask! Creepages and clearances require absolute distances, some may rely on fish paper and the above methods to accomplish that feat. Safety must be first.