Explanation · for Engineers, Developers
Devices, profiles and tags
What a device, a device profile and a tag are in Proxus, how they relate, and what the data types and quality of a value mean.
Three objects describe every machine Proxus reads: the device (this machine), the device profile (how to talk to machines of its kind) and its tags (the values to read). Splitting them this way lets you describe a kind of machine once and add the tenth one in a minute.
Device
A device is one machine, PLC, robot, meter or sensor that Proxus reads. It holds what is particular to that one machine:
| Part | Meaning |
|---|---|
| Device name | Unique in the installation. Most plants use site, line and equipment, such as LYS_MIXER_03. |
| Address | Where the machine is on the network (IP address and port), and the reading interval if it differs from the profile. |
| Gateway | The one edge gateway that reads it. |
| Device profile | The one profile it uses. |
| Place | Enterprise, Site, Area, Process cell and Equipment module. All optional. The place sets the device's path in the Unified Namespace and how lists group devices. |
| Device type | What the machine is (Mixer, Pump, Filler / Packaging...). It sets the icon and how the Operations Center shows the device. You choose it; Proxus does not guess it. |
| Outbound targets | Where its values go besides the historian. |
| Active | Whether the gateway reads it. Clear it to stop reading without deleting the device. |
A device belongs to exactly one gateway and one profile. To read the same machine from two gateways, add two devices.
Device profile
A device profile says how to talk to a kind of device:
- the protocol (Modbus TCP, Siemens S7, OPC UA, MTConnect, the simulator...);
- the connection parameters of that protocol (byte order, unit ID, rack and slot, security...);
- the list of tags.
Many devices can share one profile. A change to the profile, such as a new tag, applies to every device that uses it; the profile's Used By list shows which ones. The device setup wizard creates a profile when you add a device, under the Profile name you give it, and offers it under Start from the next time.
Tag
A tag is one value read from a device: a temperature, a speed, a counter, a state. Each tag in a profile has:
| Field | Meaning |
|---|---|
| Name | The name the value has everywhere in Proxus: on the device page, in trends, in the UNS topic. |
| Address | Where the value is in the device, in the protocol's own form: a register (x=3;0 for Modbus holding register 0), a Siemens address (M10), an OPC UA node, or a range such as [0,100] for the simulator. |
| Type | The data type the device holds the value in. See the table below. |
| Unit | The engineering unit (°C, rpm, %), shown next to the value and published with it. |
| Polling interval | A reading interval for this tag only. Empty or 0 uses the profile's interval. |
Data types
The data types a tag can have. The first name is the one used in Proxus, the second the IEC 61131-3 name a PLC programmer uses.
| Type | IEC 61131-3 | Size |
|---|---|---|
| Bool | BOOL | 1 bit |
| Short | INT | 16 bit |
| UShort | UINT | 16 bit |
| Int | DINT | 32 bit |
| UInt | UDINT | 32 bit |
| Float | REAL | 32 bit |
| Long | LINT | 64 bit |
| ULong | ULINT | 64 bit |
| Double | LREAL | 64 bit |
| String | STRING | variable |
| Bytes | ARRAY OF BYTE | variable |
| DateTime | DATE_AND_TIME |
Choose the type the device stores the value in, not the type you would like to see. A Float read as Int gives a wrong number. To convert or scale a value, use a pipeline.
Quality
Every value carries a quality, shown in the Quality column of the device page and stored with the value:
| Quality | Meaning |
|---|---|
| Good | The gateway read the value and it is current. |
| Bad | The read failed. The value field holds the reason, for example a wrong address or a timeout. |
| Uncertain | The tag failed several reads in a row, so the gateway set it aside. It tries the tag again from time to time, and the value shows the last error. |
A tag with Bad or Uncertain quality does not stop the other tags of the device; they keep being read. When the whole device does not answer, the gateway marks the device as not connected and tries it again at growing intervals.
What's next
- Add a device with the setup wizard.
- Device profiles explains how to edit a profile and its tags.
- Wrong values or bad quality helps when tags do not read well.
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