Devices measuring either „Density “, „specific density “ or “el. conductivity” use physical measurement methods and thus show different values if water temperature changes! This is due to different density of water at different temperatures (physical effect).
Measured values of identical salt water will be :
(Try it! Gather some water of your tank and measure salinity it in a separate device. Allow ~1h for cooling down and measure again)
For measuring we have to regard that temperature in our tanks is going slightly up/down. If we don’t take care if it, salinity measured might be incorrect!