How to change a number from payload

General
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Hi!, i'm struggling with my DHT22 sensor. If i do the calibration, the sensor is 5% humidity to high according from 2 other callibrated measuresment tools. Now i thought, maybe i can change the value from the sensor -5. Is there someone how did this or knows how to do this? This is my current situation in node-red

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2

You could use a change node as follows -

[{"id":"5e31270904648203","type":"change","z":"624963ed82f87a01","name":"","rules":[{"t":"set","p":"payload.humidity","pt":"msg","to":"payload.humidity -5","tot":"jsonata"}],"action":"","property":"","from":"","to":"","reg":false,"x":1390,"y":280,"wires":[["e6ef0f9ea7d918ec"]]},{"id":"4d3938590c6cf87d","type":"inject","z":"624963ed82f87a01","name":"","props":[{"p":"payload"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","payload":"{\"temp\":5,\"humidity\":10}","payloadType":"json","x":1190,"y":280,"wires":[["5e31270904648203"]]},{"id":"e6ef0f9ea7d918ec","type":"debug","z":"624963ed82f87a01","name":"","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"true","targetType":"full","statusVal":"","statusType":"auto","x":1570,"y":280,"wires":[]}]
3

Here is a link to an interesting article about these sensors:

Which may be helpful to understand these devices.

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