SIL1 figures for Signal Conditioning

Omniflex have released reliability data for their Omniterm range of universal input signal transmitters, current loop isolators and trip amplifiers, for SIL calculations. The results show that calculated PFD complies with IEC61508 SIL1 requirements. The OMNITERM TXB is a 24Vdc-powered universal-input transmitter, which accepts mA, Volts, thermocouple and RTD inputs and provides universal output, selectable between milliAmps (4-20 or bipolar), volts or pulses (frequency). The product is designed for SIL1 safety loops and achieves the reliability parameters specified by IEC61508 for this level. For any use in safety-related applications: * The TXB must be used within its electrical and mechanical specifications. * The EMC environment must be typical industrial environment (IEC61000-4-4 Level3 or IEC61000-4-3 Class3). * To maximise diagnostic coverage, input must be used in configuration such as 4-20mA, 1-5V or TC with burnout detection where signal loss can be detected as a fault (see product configuration advanced settings). * Output to be used in configuration such as 4-20mA or 1-5V where signal loss can be detected as a fault. The OMNITERM TTB is a dual trip amplifier, which accepts mA or Volts input and provides two trip relays with changeover contacts. The unit provides wire-break detection function, which will de-energize both relays when input signal is lost. For any use in safety-related applications:. * The TTB must be used within its electrical and mechanical specifications. * EMC environment must be "typical industrial environment" as specified in IEC61000-4-4. * The relays must be set as "de-energized to trip". * The output circuits must be connected to the Normally Open contacts (closed when output relay is energized). The OMNITERM LPI is a loop-powered isolator. It accepts mA input in the range 4-20mA. The output current is equal to the input current, within limits of product specification. The unit provides internal precision 250 Ohm resistors to convert 4-20mA current signal into 1-5V voltage signal. For any use in safety-related applications:. * The LPI must be used within its electrical and mechanical specifications. * EMC environment must be standard industrial environment. * Low output current <3.6mA must be detected as a fault and this condition must result in actuators being placed in a safe state. The datasheets available from Omniflex provide reliability figures only. In safety-related applications it is the user responsibility to comply with all the other requirements of IEC61508 which may be applicable to the safety system in question.

For more information on SIL1 figures for Signal Conditioning talk to Omniflex UK Limited