www.sensirion.com / D1

Version 3.3 – November 2024

5 / 23

2

Sensor specifications

2.1 Sensitivity to compensation inputs of low-cross-sensitivity mode

The STC31-C should be provided with inputs for temperature (T), relative humidity (RH) and pressure (p) to

compensate environmental conditions – see Sections 3.3.3 to 3.3.5. Without external input, the sensor will take

its internal temperature and assume RH=0%, p=1013 mbar. Inaccurate environmental inputs affect the STC31-

C output, by an amount which depends on the selected measurement mode. The table below describes the

additional inaccuracies resulting from errors of the input parameters in the vicinity of the true values.

Condition

Selected Range

Typical additional STC31-C output error (vol.%) due to:

0.1°C error in T

1% error in RH

1 mbar error in p

T=30 °C, RH=30%,

p=1000 mbar, c=0.0%

0-40 vol%

0.025

0.0002

0.0001

0-100 vol%

0.06

0.04

0.01

The sensitivity to errors in the compensation inputs is significantly higher for the low-noise mode.

2.2 Temperature

The measured temperature is the temperature of the bulk silicon in the sensor. This temperature value is not

only depending on the gas temperature, but also on the sensor’s contact surface (PCB) and other surroundings.

See the Engineering Guide for more details. Values are determined for the measurement frequency of 1 Hz.

Parameter

Value

Measurement range

-40 °C to 105 °C

Resolution

16 bit

Accuracy

0.5 °C (25 °C to 60 °C),

1.0 °C (10 °C to 90 °C), 1.5 °C (-30 °C to 100 °C), 2.0 °C (-40 °C to 105 °C)

Repeatability

0.1 °C

2.3 Electrical specifications

Parameter

Symbol

Condition

Min.

Typ.

Max.

Units

Supply Voltage

VDD

2.7

3.3

5.5

V

Power-up/down level

VPOR

2.3

2.5

2.7

V

Supply current

IDD

Measuring

3

5

mA

Idle state

50

uA

Sleep mode

1

uA

2.4 Timings

Parameter

Symbol

Typ.

Max.

Units

Comments

Power-up time

tPU

14

ms

Time to sensor ready

Soft reset time

tSR

12

ms

Time between soft reset command or

exit sleep mode and sensor ready

I2C SCL frequency

fI2C

400

1000

kHz

Low-cross-sensitivity

concentration

measurement duration

110

ms

Measurement result is returned

together with temperature value

Low-noise concentration

measurement duration

75

ms