SI7020-A10 Datasheet, PDF (22/34 Pages) Silicon Laboratories – Excellent long term stability

Si7020-A10
5.1.1. Measuring Relative Humidity
Once a relative humidity measurement has been made, the results of the measurement may be converted to
percent relative humidity by using the following expression:
Where:
%RH = ¹----²---⁵----^-₆--^R-₅---^H-₅---₃-^_--₆-^C----^o----^d---^e-- – 6
%RH is the measured relative humidity value in %RH
RH_Code is the 16-bit word returned by the Si7020
A humidity measurement will always return XXXXXX10 in the LSB field.
Due to normal variations in RH accuracy of the device as described in Table 4, it is possible for the measured value
of %RH to be slightly less than 0 when the actual RH level is close to or equal to 0. Similarly, the measured value
of %RH may be slightly greater than 100 when the actual RH level is close to or equal to 100. This is expected
behavior, and it is acceptable to limit the range of RH results to 0 to 100%RH in the host software by truncating
values that are slightly outside of this range.
5.1.2. Measuring Temperature
Each time a relative humidity measurement is made a temperature measurement is also made for the purposes of
temperature compensation of the relative humidity measurement. If the temperature value is required, it can be
read using command 0xE0; this avoids having to perform a second temperature measurement. The measure
temperature commands 0xE3 and 0xF3 will perform a temperature measurement and return the measurement
value, command 0xE0 does not perform a measurement but returns the temperature value measured during the
relative humidity measurement.
The checksum output is not available with the 0xE0 command.
SequencetoreadtemperaturevaluefrompreviousRHmeasurement
S
Slave
Address
W A

0xE0
A Sr
Slave
Address
R A
MSByte
A LSByte NA P
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Rev. 1.1