Screens and Harvesters

Screen

A screen is one physical display.

Vojo reports facts about a screen. It doesn't tell you whether a screen is on, off or working, and there's no online status to read. Two facts tell you what Vojo has seen:

• last_evidence_at is the reported time of the newest Passport or Harvester event in the screen's latest play, or null if there isn't one. That's the time the event reports, which may not be when Vojo received it. Current Harvesters round that time down to a 10-minute bucket, and an event that hasn't been matched into a play doesn't count, so allow for both when you decide how old is too old.
• harvester and quality_bad tell you which Harvester is paired to the screen, if any, and whether that Harvester currently reports a quality problem.

Draw your own conclusion from these. For example, you might alert when a screen scheduled to be playing has had no evidence for an hour.

Harvester

A Harvester is Vojo's optical sensor, fixed to the glass of a screen. It reads the fingerprint of whatever is being shown, which gives Vojo evidence that doesn't depend on anything running on the screen's own device.

This is Proof of Display: confirmation that a creative actually appeared on the screen, not just that it was sent there.

A screen doesn't need a Harvester. Running with Passport alone is normal, but it limits how high a play can score: see Plays and verification scores.