This article will discuss the difficulty of high dynamic range measurements, the role of high-definition oscilloscopes, and how they can be used effectively for high dynamic range measurements.
input signal the oscilloscope can handle to the smallest signal amplitude it can detect. Resolution is generally quantified by the number of bits in the analog- to-digital converter (ADC). The resolution is equal to 2 raised to the power of the number of bits. As such, an 8-bit converter has a resolution of 28 or 256:1. A 12- bit converter has a resolution of 4096:1, which is 16 times greater than an 8-bit converter. For years, digital oscilloscopes offered 8-bit resolution in higher bandwidth oscilloscopes. This is because of an engineering tradeoff in ADCs that makes resolution, measured by the number of bits, inversely proportional to the ADC’s maximum sampling rate. About eight years ago, Teledyne LeCroy pioneered 12-bit oscilloscopes termed high definition or ‘HD’ oscilloscopes. They have recently added the WaveSurfer 4000HD series to the HD product line. The series includes four oscilloscopes with bandwidths of 200, 350, 500, and 1000 megahertz (MHz). They all sample at 5 Gigasamples per second (GS/s) which is very respectable for a 12-bit oscilloscope. Internal mixed- signal digital inputs, DVM, function generator and frequency counter are available to round out this multi- instrument offering. The family offers all of this along with 12-bit resolution at a reasonable price point.
scope input and so will be hard to measure unless the instrument has a high resolution. The problem is that higher sensitivity in the presence of a larger signal or offset requires higher resolution scopes, and these typically are costly, especially for a quality scope with low noise inputs. Higher resolution without a lower noise floor is useless. What designers and developers need is a reasonably priced 12- bit scope with a low front-end noise floor. One solution to this need for high resolution with front-end low noise at low cost is Teledyne LeCroy’s WaveSurfer 4000HD series of high definition oscilloscopes. This article will discuss the difficulty of high dynamic range measurements, the role of high-definition oscilloscopes, and how they can be used effectively for high dynamic range measurements. Oscilloscope vertical resolution Oscilloscope vertical resolution refers to the ratio of the highest
There are many applications where designers and test and measurement engineers need to make wide dynamic range measurements to look at very small signals in the presence of large signal amplitudes. Power integrity assurance, echo location and ranging systems like radar and sonar, medical imaging systems such as nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI), as well as non-destructive testing using ultrasound, are among these types of applications. Oscilloscopes are of course the go-to tool for making these measurements in the system development and prototyping stages, but these are primarily limited by the vertical resolution of the scope’s front-end. For example, an 8-bit oscilloscope has a dynamic range of 256:1, so on a 1 volt range, the theoretical minimum signal is 3.9 millivolts (mV). When trying to view millivolt level ripple signals on a 3.3 volt bus, higher sensitivity and offset range are needed. Also, when using high attenuation probes to prevent circuit loading, signal levels will be attenuated at the
Fundamentals of 8 versus 12-bit oscilloscopes and how to use modern 12-bit scopes Written by Art Pini
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