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Version 3.3 – November 2024

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Product revision notice

The development the STC family has resulted in major advances and a new

measurement mode with superior cross sensitivity performance is introduced with

the 2024 release of the STC31-C.

The STC31-C can be identified visually by the laser marking on the package: STC31

”C”. The previously available version of the STC31 was marked with an “A”.

Changes are:

•

Introduction of the new standard measurement mode (low-cross-sensitivity) with significantly reduced

cross sensitivity to changes in the humidity and oxygen content of the air. The legacy measurement

mode (low-noise) is still available with unchanged measurement command for backward compatibility

(see below).

•

Applies to the new standard low-cross-sensitivity measurement mode:

•

General improvements of the temperature and pressure sensitivity.

•

Improved characterization of the impact of concentration, temperature, humidity and

pressure on the measurement accuracy. See section 1.1.

•

Characterization of the sensitivity to errors in the compensation inputs (T, RH, p). See section

2.

•

Extension of the low concentration range from 0-25% to 0-40% CO2.

•

The new standard measurement mode (low-cross-sensitivity) has more noise on the individual

measurement than the low-noise measurement mode. This can be resolved by averaging

multiple measurements or using the filter setting.

•

Detailed characterization of the temperature sensor accuracy. See section 2.2.

•

Increased absolute minimum and maximum temperature ranges. See section 2.7.

•

In contrast to STC31, STC31-C’s center pad is not connected to ground, and it is recommended to

solder it to ground and not let it floating.

Backward compatibility:

•

The STC31-C is fully backward compatible to the STC31.

•

There are no changes in the physical properties of the component and shipping package.

•

There are no changes in the electrical interface or digital communication.

•

The new standard measurement mode (low-cross-sensitivity) is now available under a new

measurement command argument (see section 3.3.2) and does not overwrite the legacy measurement

mode (low-noise).

•

The low-noise measurement mode remains available with the same measurement command argument

and there is no change of the communication required to continue using it when transitioning from

STC31 to STC31-C.

•

The new measurement mode (low-cross-sensitity) seems to perform better for all applications known

to us. We recommend all customers to evaluate it. However, no end of life of the old measurement

mode is planned.

•

The unchanged specifications for the low-noise mode are provided unchanged in section 1.2.