Applications of Low Power Measurement in Humidity Sensors

Sensirion’s SHTC1 humidity and temperature sensor is suitable for applications requiring minimal power consumption. The sensor offers a dedicated low power measurement mode with a definite set of commands, as shown in Table 1. However, it should be noted that measurements in low power mode have higher noise on the physical sensor output.

Table 1. Measurement commands for low power measurement mode.

Measurement Commands for Low Power Mode
Clock Stretching Enabled Clock Stretching Disabled
Read T First Read H First Read T First Read H First
0x6458 0x44DE 0x609C 0x401A

Low Power Measurement Mode

The low power mode considerably reduces the duration of measurement and thus reduces the energy usage per measurement (Table 2).

Table 2. Characteristic values for measurements in low power mode.

Parameter Min. Typ. Max. Units
Measurement Duration   0.71 0.94 ms
Supply current during measurement   230 380 ìA
Energy consumption per measurement   0.3   ìJ
RH repeatability1   0.2   %RH
T repeatability1   0.3   °C

1 The stated repeatability is 3 times the standard deviation (3ó) of multiple consecutive measurement values at constant conditions and is a measure for the noise on the physical sensor output.

It should also be noted that the advantage of lowest possible power consumption results in reduced noise performance and repeatability of the T and RH output when compared to the traditional measurement mode, as shown in Table 2. This can be vital if the sensor signals are utilized for data post-processing. Hence, low power mode is not recommended when T and RH signals are utilized for data post-processing.

Furthermore, when low power mode is used, the 12C bus must be free of communication whilst the SHTC1 humidity and temperature sensor is measuring. During the measurement, activity on the SCL line may further impact the repeatability of the sensor signals.

Conclusion

For reduced power consumption, the SHTC1 sensor offers a low power measurement mode with an explicit set of commands.

This information has been sourced, reviewed and adapted from materials provided by Sensirion.

For more information on this source, please visit Sensirion.

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