I had nearly the same conversation with a client last year (greenhouse, not open field), so here’s how I ended up explaining it, mapped to what Hermetry actually has.
IoT is the bottom layer: devices, a way in, and stored data. For you that’s the ESP32 nodes on MQTT, the industrial PC on the pivots, telemetry history, and the alarm rules on the soil profile. That part you clearly have.
The “4.0” story is about three extra things on top of that:
- a model of the operation, not just a list of devices: where each thing is, what belongs to what
- closing the loop: data changing what machines do, not only charts people look at
- connecting the floor to the business side (planning, maintenance, ERP)
In Hermetry those map pretty directly. The model is Sites & Assets (Hermetry Twin): build field > pivot > zone, place the devices on it, and each place rolls up the worst status and open alarms of the devices under it. Closing the loop is the Rules card or a flow sending a command to the pivot when moisture stays low (the pivot panel would need to accept commands over MQTT for that). The business side is webhooks, the REST API or forwarding from a flow into whatever system they use.
If he asks about MES or a “production” module: Hermetry Forge is on the product list, but I couldn’t find a doc page for it, so ask sales what it covers before you promise anything in the meeting. Everything above you can build with what you already have.
The getting started overview has a decent one-page picture of the pieces if you want something to show him: Getting started.