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3.4.4 set_rht_compensation

External relative humidity (RH) and temperature (T) compensation values can be written through the

set_rht_compensation command when the SHT4x is not controlled by STCC4 through the dedicated I2C

controller interface (see Section 2.5). The RH and T values must be provided from the same RHT sensor. The

written RHT values are utilized for RHT compensation after a maximum of one measurement interval. The

default or last written values are used for RHT compensation until overwritten. Power cycling resets the values

to the default values of 25 °C and 50 %RH. See Section 3.5 for the signal output and input conversion. Do not

use the set_rht_compensation command when an SHT4x is controlled by STCC4 through the I2C controller

interface.

Command

Command

Hex Code

Argument

Consecutive

Read

Execution

Time (ms)

Description

set_rht_com

pensation

0xE000

Byte0: Temperature 8msb

Byte1: Temperature 8lsb

Byte2: CRC

Byte3: Relative humidity 8msb

Byte4: Relative humidity 8lsb

Byte5: CRC

-

1

Writes the RHT values for

compensation.

Example for 25 °C and

50 %RH:

[0xE0, 0x00, 0x66, 0x66,

0x93, 0x72 0xB0, 0xDC]

3.4.5 set_pressure_compensation

External pressure values can be written through the set_pressure_compensation command. The written pressure

value is applied for pressure compensation after a maximum of one measurement interval. The default or the

last written value is used in pressure compensation until overwritten. Power cycling resets the sensor to the

default value of 101’300 Pa. See Section 3.5 for the signal output and input conversion. Input values are clipped

to a range between 40’000 – 110’000 Pa.

Command

Command

Hex Code

Argument

Consecutive

Read

Execution

Time (ms)

Description

set_pressure

_compensat

oin

0xE016

Byte0: Pressure 8msb

Byte1: Pressure 8lsb

Byte2: CRC

-

1

Writes the pressure value.

Example for 101’300 Pa:

[0xE0, 0x16, 0xC5, 0xDA, 0x83]

3.4.6 measure_single_shot

The measure_single_shot command conducts an on-demand measurement of CO2 gas concentration.

Command

Command

Hex Code

Argument

Consecutive Read

Execution

Time (ms)

Description

measure_sin

gle_shot

0x219D

-

-

500

Performs a single shot

measurement.

Recommended operation sequence:

1. Wake the sensor up from sleep mode to idle mode with the exit_sleep_mode command (Section 3.4.8).

2. Send the measure_single_shot command and wait for the specified execution time.

3. Send the read_measurement command (Section 3.4.3) and wait for the specified execution time.

4. Read out the measurement data.

5. Set the sensor to sleep mode with the enter_sleep_mode command (Section 3.4.7).

6. Wait before the next measurement. A sampling interval between 5 s and 600 s (10 minutes) is recommended

to ensure proper operation of the ASC algorithm.

7. Repeat steps 1-5 as required by the application.