Maximum accuracy limit: Only sensors measuring
within the maximum accuracy limit band qualify for
sales. Hence, no sensors with tolerances outside the
maximum limits are shipped to customers. Furthermore,
a process capability index Cpk = 1.33 is targeted.
Maximum accuracy limits are specified for the full range
of supply voltage if not stated otherwise. In general the
specification is valid at 25°C; however, for SHT2x there
is an extended specification for temperatures 0 – 80°C.
Hysteresis
The hysteresis value is the difference of measured
values of the same sensor at a certain log point
accruing from dry environment on one hand and humid
environment on the other hand – giving enough dwell
time. With other words, humidity sensors carry some
memory of conditions experienced in recent past:
Sensors with dry history carry some negative offset
while sensors with humid history carry some positive
offset. Hysteresis appears due to composition and
design of the sensor element.
As the hysteresis does not depend on quality of
calibration but is dependent on exposure range in the
application, this value is understood to be additional to
calibration accuracy.