Field notes

Things worth writing down after the van is packed.

A reference meter settles arguments

Bring one, clamp it alongside the installed sensor, log both for an hour. Half of the "your system is wrong" calls in the first month are answered by a photograph of two traces lying on top of each other, and the other half are real and worth finding early.

Buffer sizing is a calendar problem, not a storage problem

Nobody loses a link for four hours. They lose it over a public holiday, when the only person with a key is away. Size the buffer to the longest plausible gap in the site's staffing calendar and the storage cost stops mattering.

Label the loop, not the wire

Wire colours get reused when a panel is repaired. A printed loop number on both ends survives the repair and the person who did it.

Alarm fatigue is a threshold problem

A limit set at the datasheet maximum will fire on every startup transient. Set it from a fortnight of the site's own data, then explain the number to the operator who will be woken by it. If they cannot repeat the reasoning back, it is the wrong number.