Set up · tab 3
Tags and signals
The gateway lists the tags it can see; in Nexa you pick the ones that matter and say what each one is. A tag becomes a signal of a machine only once it is linked.
Send the tag list
On tab 3. Tags:
- Pick the Server, if the gateway reads more than one.
- Optionally type part of a path in Only paths containing, such as the machine’s name in TOP Server, to keep the list short.
- Click Browse the server. Each tag is listed with its current value, up to 5,000 tags.
- Click Send to Nexa. With rows selected, the button sends only those (Send 12 selected); otherwise it sends them all.
Sending the list does not start any data flowing. It only lets Nexa show the tags so you can choose.
Link tags to the machine
In Nexa, back on the machine’s Live tab, under Machine link settings:
- Under 2. Tags found on the plant’s OPC UA server, click Refresh if the list is empty. Each tag shows the value it had when it was read, which helps tell similar tags apart.
- Click Link on a tag, then choose What it is (see below), give it a Name people will understand, and a Unit for measurements. Click Save.
- The tag moves to 3. Signals linked to this machine.
The gateway picks up new links within a minute, with no restart, and starts reading those tags.
What a tag can be
What it is tells Nexa how to read the tag. Choose carefully for running, fault and the counters: they drive the machine’s state, its alarms and its production counts.
What the machine does
| Role | What it means |
|---|---|
Runningrunning | On while the machine produces. Drives running and stopped time. |
Faultfault | On, or a non-zero code, while the machine is in fault. Each fault becomes an alarm in Nexa, and opens an unplanned downtime. |
Good parts countergood_count | A counter that goes up by one per good part. Nexa receives the parts made each minute. |
Rejected parts counterreject_count | The same, for rejected parts. |
Cycle countercycle_count | The same, per machine cycle. |
Temperaturetemperature | A measurement. Nexa keeps the minimum, maximum, average and last value of each minute. |
Pressurepressure | A measurement, as above. |
Speedspeed | A measurement, as above. |
Vibrationvibration | A measurement, as above. |
Energy (kWh)energy_kwh | An energy meter reading. |
Other measurementother | Any other number worth a chart. |
Operating context
Settings rather than measurements. Each change of value is logged as a setting change and marked on the machine’s chart, so a drift can be traced back to the change that caused it.
| Role | What it means |
|---|---|
setpoint | A numeric setting, such as a target temperature or speed. |
recipe | The active recipe or program, as a number. |
mode | Automatic, manual, setup… as a number. |
flag | A configuration switch, such as a quality check being enabled. |
A good first set
Start small and add later. For most machines, these four tell you most of what you need:
- Running, so Nexa knows when the machine produces.
- Fault, so stops are recorded with their cause.
- Good parts counter, and the rejected one if the PLC has it.
- One measurement that tends to drift before a failure, such as a motor temperature.
Then decide what may leave the network in Sending rules, or go straight to Run and monitor.