Tektronix previews 1 GHz b/w optical isolation for power measurements

March 16, 2016 // By Graham Prophet
Power electronics designs using new, fast semiconductor switches in GaN or SiC technology are among the target uses for measurement technology disclosed by Tektronix, which offers complete galvanic isolation for oscilloscope signal connections, and CMRR of up to 120 dB.

IsoVu provides galvanic isolation between a device under test (DUT) and an oscilloscope through the use of electro-optical sensors. It will, Tek says, be the first measurement solution capable of accurately resolving high bandwidth differential signals in the presence of large common mode voltage. The technology will also offer immunity to external interference and radiated emissions, minimising the impact of EMI on measurements.


Tek asserts that engineers working on power device designs involving GaN and SiC technologies and other high-speed applications have had no way to accurately visualise differential signals when common mode interference is present. Engineers also face challenges making measurements in noisy environments or those that have high EMI.


The IsoVu technology employs an electro-optic sensor to convert the input signal to optical modulation, which electrically isolates the device-under-test from the oscilloscope. IsoVu will incorporate four separate lasers, an optical sensor, five optical fibres, and feedback and control techniques. The sensor head, which connects to the test point, has complete electrical isolation and is powered over one of the optical fibres.


IsoVu technology offers greater than 120 dB common mode rejection from DC to 100 MHz which Tek asserts is around 90 dB better than previously available measurement systems. At 1 GHz, it will provide 80 dB (10,000:1) common mode rejection at 1 GHz, which is more than a thousand times (60 dB) better than previously available measurement systems.


Using this technology, engineers will be able to accurately measure small differential signals (5 mV - 50V) in the presence of large common mode voltages less than 2 kV from DC to 1 GHz. This will be the first signal acquisition product, Tek adds, where the common mode voltage capability does not de-rate over bandwidth.


Tektronix plans to offer a 10m fibre optic cable option with the same performance specifications as the 3m option to allow users to move their test system away from