Set the gain so the signal fits the range. Inputs must stay between ground and the supply voltage.
What the message means
The converter reports raw counts. The gain setting decides the full-scale voltage and the size of one count.
Fix it in this order
- Run an I2C scan and note the address set by the ADDR pin.
- Choose the gain for your signal, such as 4.096 V full scale.
- Convert counts to volts with the matching step size.
- Keep every input between ground and VDD.
- Use single-ended channels with a common ground.
- Average readings to reduce noise.
Why it happens
The ADS1115 returns raw counts, and the voltage per count depends on the gain setting. With the default range of about 6.144 V a count is 0.1875 mV, and a different gain changes it. Its address depends on the ADDR pin: ground gives 0x48 and VDD gives 0x49. An input must stay within the supply range.
Set the gain to match your signal, convert counts with the right factor, and run an I2C scanner to check the address.
If you see this, do this
| You see | Do this |
|---|---|
| Reads full scale | Gain too high for the signal. |
| Not found | Address or wiring. |
Related
Last reviewed: November 2026. These are the usual causes and the order that finds them fastest. Test on your own board; clones and cables differ.