Test & Measurement

New scope offers four true differential channels

8th March 2017
Mick Elliott

The PicoScope 4444 high-resolution differential oscilloscope is launched today (March 13) by Pico Technology. This instrument features four true differential input channels and a range of accessories for measurements from millivolt to 1000 V CAT III applications. This new PicoScope addresses the perennial problem of making accurate voltage waveform measurements on circuit elements that are not ground-referenced, without the risk of short circuits that could damage the device under test or the measuring instrument.

“Building on the success of PicoScope 4000 Series high-resolution oscilloscopes, the PicoScope 4444 gives electrical engineers the freedom to make differential voltage measurements in the presence of common-mode signals,” said Trevor Smith, Business Development Manager, Test & Measurement, at Pico Technology. “The new instrument has 14-bit resolution on four channels and 256 megasample capture memory, so is ideal for precise analysis of complex waveforms ranging "from biomedical sensors to current probes and 1000 V CAT III power distribution circuits.” 

Scientists and electronics engineers frequently need to make low-voltage measurements in the presence of high common-mode noise or varying offset voltages.

Ground-referenced oscilloscopes require use of two input channels and an A–B math function to observe the differential signal of interest.

But, as well as this requiring two input channels, most scopes don’t have a high enough common-mode rejection ratio (CMRR), nor the resolution to make measurements with sufficient precision. 

Engineers working on polyphase power distribution systems need to measure phase-to-phase AC voltages, rather than phase to ground. A ground-referenced scope can’t be used as it will cause a short circuit.

External differential probes are a solution but they are quite expensive and cumbersome, with each probe requiring its own power supply.  

The PicoScope 4444 has differential inputs and a choice of 1:1 low-voltage and 25:1 1000V CAT III probes to address both of these problems. 

Furthermore, the scope has a novel intelligent probe interface that, in addition to delivering the differential signal to be measured, can also provide power for active probes such as Hall Effect AC/DC type active current probes.

The scope detects when a compatible probe is connected and sets the corresponding units and vertical settings in the PicoScope 6 software.

Compatible probes available at launch are the PicoConnect 441 passive differential 1:1 20 MHz voltage measurement probe, the PicoConnect 442 1000 V CAT III passive differential 25:1 10 MHz voltage measurement probe, the TA300 40 A AC/DC 300 V CAT III, 100 kHz current measurement probe, the TA301 200/2000 A AC/DC, 150 V CAT II, 20 kHz, current measurement probe, the   TA299 D9-dual BNC adaptor and the TA271 D9-BNC adaptor.

The PicoScope4444 is available now at distributors

 

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