---
title: Adding measurements to an MQTT (JSON) collector
slug: how-tos/IeSgE1jvJ5cXOY1F5CYc0
docTags: NdAmj9E8yTRkwQ9gl8SF9,11HRbizM9olUCcNKOmSMd,db2K1XGTHf4IBn7zhpSb4
createdAt: 2025-09-24T13:00:34.872Z
---

Once the collector is connected, you can add one or more measurements. A measurement defines how data from a subscribed topic is mapped into Historian.

To create a new measurement manually, go to the **Measurements** page in Historian and click **+ Create Measurement**.

You can find JSONPath documentation online, and [jsonpath.com](https://jsonpath.com) is a useful tool to quickly test expressions against sample messages before configuring them in Historian.

**Example configuration:**
Assume your broker publishes the following JSON message on topic factory/machine1/metrics:

```json
{
 "temperature": 23.5,
 "pressure": 1012,
 "status": "Good",
 "machineId": "Mixer-01",
 "ts": "2025-09-18T09:45:00Z"
 }
```

You can configure a measurement with:

- **MeasurementPath**: $.temperature
- **TimestampPath**: $.ts
- **StatusPath**: $.status
- **TagNamesAndTagValuePaths**: \{"machine": "$.machineId"}

If the timestamp is in UNIX format, set TimestampLayout to UNIX, UNIXMILLIS, UNIXMICROS, or UNIXNANOS. Otherwise **RFC3339** is assumed.

Expected outcome:

- The measurement status changes to Good within a few seconds.
- Live values appear in the data preview panel.
- The measurement shows up in the configured measurements list.