Calibration

This page explains what you can adjust on WallSense and how to make a good comparison. In the current firmware you can correct temperature and humidity and recalibrate CO2. Radar tuning will follow with release firmware.

Note: This page describes the current firmware, a WiFi test build. Names and behavior can change until release.

What You Can Adjust

How to Make a Good Comparison

In a wall box, temperature depends on the installation. Compare after hours of stable running, with a reliable reference.

1. Let WallSense run for hours without changes. Do not judge it right after a start.
2. Keep the rear LEDs off, because LEDs that burn brightly for a long time give off some heat.
3. Hold or place a reliable thermometer and hygrometer next to the front, in the same air.
4. Keep the room stable: no open windows, direct sunlight or people right next to the sensor.
5. Note a few readings of both over some time and use the average difference.
6. Set the offset, wait until the reading is stable and compare again.

Temperature and Humidity

The SHT45 is the primary climate sensor. Correct this one first.

The four offsets run from -20 to +20 in steps of 0.1, start at 0 and are kept after a restart. They are added on top of the factory correction. You can set them in Home Assistant without reflashing.

Offset = reference minus reading. Two examples:

• SHT45 Temperature shows 22.4 °C and your reference shows 21.6 °C: set SHT45 Temperature Offset to -0.8.
• SHT45 Humidity shows 48 % and your reference shows 52 %: set SHT45 Humidity Offset to 4.

Correct temperature before humidity. The firmware converts the SHT45 humidity using the corrected temperature, so a new SHT45 Temperature Offset also changes SHT45 Humidity.

The SGP41 uses the SHT45 readings for compensation, so a correct SHT45 helps VOC and NOx too.

SCD41 Extra Temperature Offset and SCD41 Humidity Offset only change the temperature and humidity shown by the SCD41. They have no effect on CO2 or on the SHT45 entities.

CO2

The SCD41 runs in low-power periodic mode with a new value every 30 seconds. Automatic self-calibration is on, so you normally leave the CO2 reading alone.

CO2 Manual Calibration forces the reading to 426 ppm in fresh air. Use it with care, because a press in stale air shifts the readings that follow.

1. Ventilate the room well for at least 3 minutes.
2. Make sure nobody is in the room.
3. Wait until SCD41 CO2 is stable.
4. Press CO2 Manual Calibration on the device page.

VOC and NOx

The SGP41 gives indices from 1 to 500, not ppm. There is nothing to calibrate. After a start or a move, allow several hours of normal operation before you judge the readings, and look at trends instead of single values.

Ambient Light

Illuminance is the only lux value in the current firmware. There is no separate corrected value and no offset. Choose the thresholds for your automations from what Illuminance shows in your own room, by day and in the evening.

Radar

The current firmware has no settings for the radars. The modules can do more than the firmware shows today. These will follow with release firmware:

What you can do today:

• Check the position. Most radar problems are about placement, see the placement advice.
• Read the energy values. LD2412 Moving Energy and LD2412 Still Energy show what the radar sees in an empty room. High values point to something moving or reflecting.
• Restart the radar. LD2412 Restart restarts the module without restarting WallSense.
• Delay your automations. Use for: in a trigger, so a short gap in presence does nothing.
• Build a zone in Home Assistant. See Zone Around the Sofa.

LD2450 Coordinates

        Sensor (0,0)
           |
    -X <---+---> +X
           |
           v
       +Y distance

Y is the distance straight into the room. X is the distance left or right of the sensor. Both are in millimeters.

Related

• Sensor Definitions
• Usage
• Troubleshooting