Electronic – How to measure salinity

In order to compensate for temperature drift, you need to place your accelerometer in a temperature chamber (e.g. these) and concurrently record both temperature and raw acceleration values while slowly changing the chamber temperature over the range of interest (ideally about ~1°/minute). If your accelerometer is well placed, you know that the true value you should be measuring is [0, 0, -9.81 m/s] and any deviation has to be due to temperature drift. Based on this, you can apply some kind of fit to the measured data to build a calibration that you subsequently use to predict the drift based on the measured temperature.

My experience is the following:

• A polygonal fit of order 3 is enough to implement the calibration. Depending on the temperature performance of your particular sensor (I haven't tested it), a linear fit may be sufficient.
• The sensor gain (the factor that convert from raw value to G) is relatively immune to temperature, but the sensor offset (additive value) is temperature dependant.
• For sensor types that are prone to temperature drift, there is a high degree of sample-to-sample variation. You should thus consider calibrating every single parts.
• More recent parts, such as the LIS3DH, exhibit much lower temperature drift as older parts. This particular one could go without temperature calibration for most applications but the most demanding.

You're confusing the operating specifications of the chip with the readout format.

Basically, the Electrical characteristics specify the range of temperatures at which the IC is guaranteed to work properly. This is a physical characteristic of the device. As the datasheet says Operating temperature range, e.g. this is the temperature range over which the IC is supposed to work properly. It has no relation to the theoretical range of the register containing the measurement value.

The temperature sensor readout is specified as "-1 °C/digit". Therefore, each increment of the temperature output equals one degree C. My guess would be that the value of the temperature readout would probably directly correspond to the actual IC die temperature in degrees C, though you should verify this.

The two specifications are unrelated. It's like a car speedometer. My car's speedometer goes up to ~150 miles/hour. However, it's not intended to actually be driven at those speeds. As such, the readout range (0-150 Mph) significantly exceeds the intended operating conditions (~0 - ~85 Mph), as they're different characteristics.