Tek’s IsoVu 1-GHz b/w, optically isolated probing system now shipping
We first covered the IsoVu system in March 2016 and reported its appearance at the PCIM show, 2016. Tek is now shipping the system, with pricing that starts at $12,000. [article edited to include;] EDN Europe asked Tek for some more insight into pricing; the base cost gets you a 200 MHz bandwidth TIVMO2 probe with CMRR of over 120 dB at DC, 120 dB at 100 MHz and 110 dB at 200MHz. A complete “typical setup” might comprise a single probe to look at a half-bridge circuit, or two for a full-bridge; plus, you’ll need a Tektronix scope with a VPI (probe) interface, if you don’t already own one; say €30-40k for the assembly. This, Tek re-afirms, gets you a measurement CMRR some 100,000-times better than any other alternative. Pricing scales towards the headline performance point of GHz signal capture.
The IsoVu platform uses an electro-optic sensor to convert input signals to optical modulation, electrically isolating the device-under-test from a Tektronix oscilloscope. The system incorporates four separate lasers, an optical sensor, five optical fibres, and sophisticated 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. Tek has filed ten patent applications for the technology embedded in IsoVu.
A critical advantage this technology offers for designers, such as those working on power devices involving GaN and SiC technologies, is superior common mode rejection that makes signals previously buried in common mode noise visible for the first time. IsoVu offers 1 million:1 (120 dB) common mode rejection (CMRR) up to 100 MHz and 10,000:1 (80 dB) CMRR at 1 GHz. By comparison, competitive solutions at 100 MHz offer approximately 20 dB CMRR at 100 MHz, making IsoVu 100,000 times better.
“The feedback we received from designers at [the US trade show] APEC was overwhelmingly positive, with many of them facing a critical need for the design insights IsoVu now makes possible,” said Chris Witt, general manager, Time Domain Business Unit, Tektronix. “Currently there is no measurement system on the market with IsoVu’s combination of high bandwidth, 2000V common mode voltage range and breakthrough common mode rejection ratio.”
The exemplar application that Tek cites is that of observing detailed switching behaviour of the power semiconductor device in, say, a high-power inverter, where millivolt-scale waveforms are of interest but they are “on top of” a voltage level of several hundred Volts. As well as being able to make such measurements, IsoVu brings a major safety benefit with total isolation of the measurement system from the system under test; with the optical fibre links, the oscilloscope (and the engineer) can be outside a fully-screened enclosure when needed.
Using IsoVu, engineers can accurately measure small differential signals (5 mV – 50 V) in the presence of large common mode voltages from DC to 1 GHz. IsoVu is the first signal acquisition product where the common mode voltage capability does not de-rate over bandwidth. IsoVu technology is available in six models of the TIVM Series Isolated Measurement Systems with 200 MHz, 500 MHz and 1 GHz bandwidth configurations with either 3-metre or 10-meter fibre optic cable lengths. The 10-metre cable option offers the same performance specifications as the 3-metre option and allows users to move their test system away from the interference and radiated emissions of the device under test. With this option, IsoVu is well-suited for such applications as remote testing and EMI validation.
Tektronix; www.tek.com/isolated-measurement-systems
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