The FIT (Failures In Time) rate is the standard convention in functional safety datasheets : 1 FIT = 1 failure per 10⁹ hours. It is preferred over MTBF because typical sensor / actuator failure rates are very low (tens to hundreds of FIT) and easier to compare on a linear scale.

Enter either FIT or MTBF and the other is computed instantly, plus the equivalent in years for human-friendly reading.

Typical FIT values for safety equipment :

• Pressure transmitter (4-20 mA) : 200-800 FIT
• Pneumatic actuator + ball valve : 300-1200 FIT
• Safety PLC : 50-200 FIT per channel
• Liquiphant level switch : 70-150 FIT