User manual

AHHYTM_E2.2.1

14/23

Application Note

Humidity Module

HYT

4.4 Scaling of Measurement Values

raw

and RH

raw

are the digital 16 bit values submitted by the sensor.

Humidity signal (2 bytes):

The rst top bits are status bits with following relevance:

Bit 15: CMode Bit, if 1 – element is in command mode

Bit 14: Stale bit, if 1 – no new value has been created since the last reading.

To mask the 2 top status bits in a 16 bit value, it will be linked logically with 3FFF and AND. The remaining 14 bit

represents the measured value. The masked value data now have to be scaled into physical measurement units:

Humidity values will be calculated as follows:

RH [%] = (100 / (2

- 1)) * RH

raw

0x0 complies with 0 % RH

0x3FFF complies with 100 % RH

raw

= 0x0000 to 0x3FFF (Hex) or 0 to 16383 (Dec)

Temperature signal (2 bytes):

The bits 15 to 2 represent the 14 bit measured value. Bit 1 and 0 are not used. The value data now have to be

scaled into physical measurement units:

Temperature values will be calculated as follows:

T [°C] = (165 / (2

- 1)) * T

raw

- 40

0x0 complies with -40 °C

0x3FFF complies with +125 °C

raw

= 0x0000 to 0x3FFF (Hex) or 0 to 16383 (Dec)

C-Code examples are available upon request.

Example:

Byte 1 Byte 2 Byte 3 Byte 4

31 dec 109 dec 96 dec 72 dec

bin 0001.1111 0110.1101 0110.0000 0100.1000

Humidity 14 bit right-adjusted Temperature 14 bit left-adjusted

hex 1F6D 1812

dec 8045 x 100/16383 = 6162 x 165/16383 - 40 =

49.1 % RH 22.06 % °C