Hysteresis does not include temperature, humidity, etc.
ASME B40.100 defines hysteresis in pressure gauges as:
"error, hysteresis: the difference between increasing pressure
and decreasing pressure readings at any point on
the scale obtained during a pressure cycle after friction
errors have been eliminated by tapping
Hysteresis can be determined
from the data obtained in the two pressure cycles.
It is the difference at each test point between
increasing pressure and decreasing pressure readings
taken after tapping, at the same test point, approached
from both increasing and decreasing pressure directions;
in a single pressure cycle, expressed in percentage of
span."
The hysteresis tolerance of a gauge is included in the specifications (if there is one).
For digital gauges "Accuracy error includes hysteresis, linearity, and repeatability error."
