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description: Feature for advanced users
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# Delta Filter Setting

In practice, it is not always possible to position your sensor with a clean, unobstructed view of the water surface you would like to measure. Additionally you may find that over time grass, weeds, or floating debris can impede the sensors view of the water.  All of these situations can result in sporadic interference with ultrasonic measurements and transmission of erroneous data. To help combat this situation we have added a configurable "delta based" filtering system to our sensors.

This feature  allows you to set a maximum “sensible" change between measurements so the sensor can reject noisy measurements caused by obstructions. The delta filter only applies a "soft" limit to the measurements. So, if the water level does change more rapidly than usual, the sensor will notice a consistent change and will transmit the measurements.

Delta based measurement filtering is available on all sensors with Firmware version 14 or newer. This can be installed over bluetooth from latest version of the mobile app.

If you are seeing sporadic erroneous measurements coming from your sensor, we recommend adjusting this setting.

To change the Delta Filter setting:

1\. [Connect to the sensor](broken-reference) from the Waterwatch mobile app.

2\. Enter the Measurement Scheduler settings and tap "Show Advanced".

![](https://3663084420-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-Lz-SWn24QYQug5Ln5Ib%2F-M3IwEE_PVsi27PAD5x8%2F-M3IwHE8leg8-SxxIipM%2FSet%20the%20delta%20value.png?alt=media\&token=f211754a-ffc5-4410-96ee-0de402fb63ed)

3\. Set the Delta value to a maximum sensible change between measurements. The default setting is 750mm which is essentially "off" for many situations. For a household water tank measuring at the default interval of 5 minutes, you may like to set the delta value to 50mm.

![](https://3663084420-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-Lz-SWn24QYQug5Ln5Ib%2F-M3IwEE_PVsi27PAD5x8%2F-M3IyNjkx2dP5ZS418UM%2FSet%20the%20Delta%20value.png?alt=media\&token=af11c179-0f53-4608-b773-58f7491ee7d4)

4\. Tap "apply" to save the setting to the sensor.
