> For the complete documentation index, see [llms.txt](https://docs.datacake.de/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.datacake.de/lorawan/payload-decoders/access-measurements.md).

# Access Measurements in LoRaWAN Decoders

## Concept

The global `measurements` object allows you to access the device's current measurements. It is structured like this:

```javascript
{
  "BATTERY": {
    "field_name": "BATTERY",
    "timestamp": "1600378287",
    "value": 3.301
  },
  "SOIL_CONDUCTIVITY": {
    "field_name": "SOIL_CONDUCTIVITY",
    "timestamp": "1600378287",
    "value": 121
  }
}
```

### Code Example

```javascript
function decoder() {
    
    // get current value from field in Database
    var field_in_db = measurements.FIELD_IN_DB.value;
    
}
```

## Building Counters

If you want to build absolute counters you can use the database access on a decoder in order to read the currently stored value, add a new count and store back the new and updated count. We show you how you can do that.

```javascript
function decoder(bytes, port) {
    
    // relative change between messages will reset to zero with every sensor uplink
    var relativeNumber = bytes[0]; 
    
    // get current value from field in Database
    var absoluteNumber = measurements["ABSOLUTE_CHANGE"].value;
    
    // add relative change to absolute number
    absoluteNumber = absoluteNumber + relativeNumber;
    
    // store back absolute number
    return [{
        field: "ABSOLUTE_CHANGE",
        value: absoluteNumber
    }]
    
}
```


---

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