Thermo Fisher Scientific Alpha pH 2000 - Manual (Page 51)

11.3 Appendix 3 –Simple explanation on the function of hysterisis
4 . 0 4.5 9.5 1 0 . 0 7.0
R E L A Y O F F
H Y S T E R E S I S B A N D
( D E F A U L T = 0 . 5 p H )
F O R W A R D D I R E C T I O N
R E V E R S E D I R E C T I O N
S P 1 S P 2
R E L A Y O N
S P 1 S e t t o L O
S P 2 S e t t o H I
The controller relay activates when the set-point is reached. In the reverse
direction, it does not de-activate when the value reaches the set-point.
Instead, it continues to be active till the value reaches the amount set by the
Hysteresis band.