Switch combinations in measuring a process variable In measuring a process variable 2 conditions
are measured one is high limit of process variable and other is low limit of process variable
In normal condition of a process variable both the high or low limit switchs are used in closed condition
Because during the normal behavior of a process variable if there is any abnormality (i.e. breakup in the wire of switch) then that state must be detected
Therefore the high limit switch’s combination is used in normally closed combination. While low limit switch is used in normally open combination