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Version 3 – August 2020

11/23

4.6 Measurement Commands for Periodic Data Acquisition Mode

In this mode one issued measurement command yields a stream of data pairs. Each data pair consists of one 16-bit

temperature and one 16-bit humidity value (in this order).

In periodic mode different measurement commands can be selected. The corresponding 16-bit commands are shown in

Table 9. They differ with respect to repeatability (low, medium and high) and data acquisition frequency (0.5, 1, 2, 4 &

10 measurements per second, mps).

The data acquisition frequency and the repeatability setting influences the measurement duration and the current

consumption of the sensor. This is explained in Section 2 of this datasheet.

If a measurement command is issued, while the sensor is busy with a measurement (measurement durations see Table

4), it is recommended to issue a break command first (see Section 4.9). Upon reception of the break command the

sensor will abort the ongoing measurement and enter the single shot mode.

Condition

Hex. code

Repeatability

mps

MSB

LSB

High

0.5

0x20

32

Medium

24

Low

2F

High

1

0x21

30

Medium

26

Low

2D

High

2

0x22

36

Medium

20

Low

2B

High

4

0x23

34

Medium

22

Low

29

High

10

0x27

37

Medium

21

Low

2A

e.g. 0x2130: 1 high repeatability mps - measurement per second

Table 9: Measurement commands for periodic data acquisition mode

(Clear blocks are controlled by the microcontroller, grey blocks by the

sensor). N.B.: At the highest mps setting self-heating of the sensor

might occur.

4.7 Readout of Measurement Results for Periodic Mode

Transmission of the measurement data can be initiated through the fetch data command shown in Table 10. If no

measurement data is present the I2C read header is responded with a NACK (Bit 9 in Table 10) and the communication

stops. After the read out command fetch data has been issued, the data memory is cleared, i.e. no measurement data

is present.

S

W

I2C Address

1

2

3

4

5

6

7

8

9

Command MSB

1

2

3

4

5

6

7

8

9

Command LSB

10 11 12 13 14 15 16 17 18

16-bit command

I2C write header