Reaction Times of Safety Functions

Block diagram of safety functions

Several boundary conditions are involved in calculating a safety distance.

Determination of the reaction time in the case of external commands
If an E-STOP pushbutton acts upon an evaluation device, its reaction time is added to the reaction time of the drive-integrated safety function. It will also be necessary to add the time needed to bring an accelerated axis to standstill:

• treac = tmulti + tPMC + tramp
• tmulti = Reaction time of the evaluation device is approx. 20 ms
• tPMC = Reaction time of the drive-integrated safety functions to external signals is 6 ms
• tramp = Ramp time to standstill depends on the moved mass, speed and other application dependent
  data

Determination of the reaction time when limit values are violated

If a monitoring circuit on a drive-integrated safety function is activated, it will be necessary to add the time needed to bring the accelerated axis to standstill. 

• treac = tPMC + tramp