A pressure switch does not change state at exactly the same pressure during activation and reset. This difference is called differential or hysteresis.
Activation setpoint
It is the pressure at which the electrical contact changes state according to the operation of the device.
Hysteresis
After activation, the contact usually resets at a different pressure. This prevents rapid on/off switching when the pressure is very close to the limit.
Why it matters
If hysteresis is ignored, the behavior of the pressostat during testing may be misinterpreted.
Verification
The actual operation is compared with the technical specifications of the specific model and not with general values.
