Cycle time of the internal diagnostics
Every SIL approved measuring device has an internal diagnostic routine that detects up to 95% of all possible faults in the device and, if necessary, reports them to the safety system by switching the device to the fault current.
Many devices of older development date still need 30 - 60 min for the internal diagnostics, i.e. in case of a malfunction of the safety function, the error would remain undetected for up to 60 min. In the meantime, the cycle time of the diagnostics could be reduced to 30 seconds to two minutes, so that these devices are even approved for the highest specified operating mode "Continuous Mode".
Electromagnetic flowmeter for safety instrumented systems (SIS) and high-accuracy requirements