The Sentinel IIsc Fibre-Optic-Link offers a signal bandwidth of <2kHz to >1GHz. The 50 Ohm input and output means that they can be coupled to commonly used sensors and measurement systems. A range of built-in attenuators and a low noise pre-amplifier allow the user to select the gain of the system from a nominal +21dB down to -24dB (for monitoring high level signals as high as 24dBm/10Vp-p), and up to +33dB (for detecting signals as low as -136dBm in a 1kHz measurement bandwidth). The transmitter contains four electrical inputs which allow up to four sensors to be monitored in turn, without the need to completely re-configure the measurement set-up. A calibration square-wave enables confirmation of system gain accuracy, and a buffer is provided to switch the input impedance to high impedance.

A number of tests detailed in DEF-STAN 59-411 specify the use of fibre for transporting RF measurements, including:

High Level Bulk Current Injection (Section B.2.6.3)

Low Level Sweep Current (LLSC, Section A6)

Low Level Swept Frequency (LLSF, Section A9)

Swept Onboard BCM test (Section A13)

The intense fields specified in the standard would potentially corrupt any measurements if they were transported over long lengths of coaxial cable. The Sentinel IIsc platform makes these measurements possible by providing EM hardened optical transmission modules. Test times are also reduced by providing easy to access pre amplification and connection to multiple transducers. DEF STAN 59-411 is the lastest in a number of critical test standards that have recognised the importance of signal integraty and the fact that fibre based systems are the only method of achieving this requirement.

The Sentry IIsc 250 Fibre-Optic-Link offers similar performance to the Sentinel IIsc, but is optimised for lower frequency operation (40Hz to 250MHz bandwidth). This makes the unit ideal for pulse power and lightning work for example.

An important feature of a Fibre-Optic-Link is the Spurious Free Dynamic Range (SFDR) i.e. the difference between the smallest and largest signals that may be transmitted through the link at the same time, without excessive distortion or noise degradation. PPM's links offer unparalleled dynamic range. Furthermore, the selectable gain function allows the user to shift the SFDR up or down to precisely match the signals being monitored. PPM's range of Test & Measurement Fibre-Optic-Link Systems covers every requirement of EMC testing.

Technical Specification - Sentinel & Sentry

FAQ's about Sentinel IIsc and Sentry IIsc