read data from the sensor it always shows 1023 values
The TL084 amplifier on the board is powered by the +- 9V rails. This means that the output (SIG) could be above the 5V that are powering the arduino (1023 is the highest value from the ADC).
You should use the trimpot to reduce the gain, and even better, use some additional circuit to protect the arduino ADC (clamping the maximum voltage).
More than 5.5V or less than -0.5V applied to the arduino pins may damage the microcontroller:
The product page has an important warning regarding this (source):
"Warning: This sensor’s output signal can be as high as the supply voltage (Vs). If you are using a supply voltage higher than the rest of your system can handle, we recommend using the gain potentiometer to adjust the sensor’s maximum output to an appropriate voltage before connecting the signal line to the rest of your system. Alternatively, you could lower the output voltage using an external circuit such as a voltage divider before connecting it to your microcontroller."
Here is something you can do (assuming the arduino is not damaged):
- Change your code using the analogReference function to use the internal 1.1V reference
- Do not connect the SIG pin directly to the ADC input. Use a voltage divider as shown below
- Use the board trimpot to adjust the gain accordingly
Note that in this application you may get saturated readings occasionally, so take this properly into account as required (it may or not be acceptable for your intended use). The R2 value is conservative (to allow readings below 1023) but you may need higher values (1k2, 1k5) as the battery is used or if you get a saturated analog signal.