Datasheet SGP40 (Sensirion) - 10

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Figure 8
Explanation of the VOC Index scale.
3.3 Built-in Self-Test
With the sgp40_execute_self_test command, users can perform an on-chip self-test for, e.g., in-line or end-of-line production testing. If this command is called when the sensor is in idle mode, the sensor returns to idle mode after the test (
Figure 9
). In case this command is called during VOC measurement mode (i.e., after calling the sgp40_measure_raw_signal command), the hotplate remains switched on thereafter. After 320 ms, the master can read a fixed data pattern (1 word + CRC byte) to check if the test was successful or not.
Figure 9
Possible ways of integrating the built-in self-test function.
3.4 Reading out The Sensor Serial Number
Every SGP40 sensor carries a unique serial number for identification purposes which is hard coded during sensor production. This number can be read out by using the sgp4x_get_serial_number command at any time in idle mode (
Figure 10
). After 1 ms, the chip responds with 3 words (each word followed by one CRC byte) which together constitute the serial number.
Figure 10
Process flow for reading out the serial number of the SGP40 sensor.
3.5 Sensor Start-up Behavior
The sensor starts powering-up after reaching the power-up threshold voltage of 1.7 V and enters idle mode after max. 0.6 ms. In this state, the sensor is ready to receive commands from the master. www.sensirion.com Version 1.1 – September 2021 10/19