www.sensirion.com

Version 0.8 – January 2017

8/14

5.3.3 Triggered Measurement

During a triggered measurement the sensor measures both differential pressure and temperature. The measurement starts

directly after the command has been sent. The command needs to be repeated with every measurement.

Command code (Hex) Temperature compensation

Clock stretching

0x3624

Mass flow

0x3726

Mass flow

Yes

0x362F

Differential pressure

0x372D

Differential pressure

Yes

During the 45ms that the sensor is measuring, no command can be sent to the sensor. After the 45ms the result can be read

out and any command can be sent to the sensor.

Monitoring whether or not the sensor is ready with its measurement can be done with the following methods.

Method

Available

Description

Clock stretching

Only for clock

stretching commands

The sensor starts the measurement after the triggered measurement

45ms the sensor performs clock stretching after acknowledging the

read header.

When the sensor has finished the measurement, it makes the result

available by releasing the SCL.

Polling

Only for non-clock

stretching commands

header as long as no measurement result is available.

IRQn

Always

The IRQn is always available to monitor whether the sensor is ready

with the measurement. When the IRQn is low, the sensor indicates that

a new measurement result can be read out. The IRQn is self-clearing

when the result is read-out.

sensor. In the table below the data layout of the results can be found.

Preceding

command

Consecutive read

Description

Triggered

measurement

Byte1: Differential Pressure 8msb

Byte2: Differential Pressure 8lsb

Byte3: CRC

Byte4: Temperature 8msb

Byte5: Temperature 8lsb

Byte6: CRC

Byte7: Scale Factor differential pressure 8msb

Byte8: Scale Factor differential pressure 8lsb

Byte9: CRC

After a triggered measurement command, the

results can be read out when the sensor is

finished with the measurement.

The temperature and scale factor don’t need to

be read out (every time). The read sequence

can be aborted by a NACK and a STOP

condition.