Confirm that the temperature readings are realistic, without too much variation.
Temperature is measured by a thermistor (temperature sensor) located inside the instrument head and is reported in degrees Celsius. Temperature is primarily measured to calculate the speed of sound, which is used to convert the travel time of the acoustic signal into distance. Correct temperature measurements are therefore important for determining measurement range and cell locations.
The speed of sound is also used directly when calculating current velocities (see Doppler effect). If the recorded temperature is incorrect, for example because of a malfunctioning temperature sensor, the calculated speed of sound will also be incorrect. The data can then be corrected using a speed of sound calculated from the actual water temperature. See the Speed of sound article for more details and instructions on how to correct your data using a new speed of sound.
The expected water temperature depends on the deployment location, season, water depth, and local environmental conditions. Some variation over time is therefore normal. However, the measured temperature should be realistic for the environment and should generally change smoothly. Sudden jumps, unusually large variations, or values that are clearly unrealistic for the deployment conditions may indicate a problem with the temperature sensor or the measurement conditions.
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