Sunday, December 28, 2008

Choosing the right Mixed Signal Oscilloscope for you

Over a decade ago, the 1st Mixed Signal Oscilloscope (MSO) was introduced by Hewlett Packard by combining 16 digital acquisition channels with 2 analog Digital Storage Oscilloscope (DSO) channels creating the 1st 2+16 MSO. Since the inception of the MSO, all major oscilloscope manufacturers have created various versions of the initial idea of analog channels combined with digital channels on the same screen and correlated in time.

Today we find that all major oscilloscope manufacturers offer MSO’s with various performance, price and features that can make choosing a complicated endeavor. In this article I will review the initial concept that MSO’s were based on and how they have evolved over the past decade and into the future.

The fundamental thinking behind MSO’s in the 1990’s was elegant in its simplicity:

There are a very large number of engineers working on designs centered on using 8 and 16 bit microcontrollers. These engineers shared some common traits:

  1. Their designs were always “Mixed Signal” in that they needed to work with both analog and digital signals on every board. This is true of most engineers.
  2. These engineers did not have significant digital problems in their designs thus did not want to learn or relearn how to use a Logic analyzer when trouble ensued.
  3. They often did not have the budgets for test equipment like the high end computer and communications design work going on at the same time.
  4. The signals used in these designs were typically slower in terms of clock rates typically less than 30 MHz.

The solution was obvious in hindsight but insightful in the early 90’s. Create a single viewing tool that was as easy to use and the scope that all engineers used and provide a time correlated digital waveforms on the same display.

The 1st MSO was introduced in 1990’s by HP. It was a 2+16 MSO with the top analog bandwidth of 200 MHz and maximum sample rate of 400 MSa/s and was sold for ~ $3000 USD making it a perfect fit for the customers described above.

Overt he past 10+ years we have seen a dramatic expansion of the performance available from the top manufacturers. Today you can find MSO’s with Analog bandwidths from 25 MHz to 2 GHz

RIGOL Technologies offers 2 MSO’s models with 2 + 16 digital channels with up to 1 GSa/s, 1 Meg of memory, Great display and 50 MHz and 100 MHz models for $1,195 and $1,595 this providing the lowest priced full range MSO’s on the market today.

posted by Rigol @ 11:33 AM