Did you know that you can filter out noise from your signals and increase the effective voltage resolution of your oscilloscope with a technique called oversampling? This is built in to the PicoScope software and works with all Pico PC Oscilloscopes in the ADC-200, 2000 and 3000 Series.
Oversampling works by collecting at least twice as many samples as you requested, then replacing each group of two or more adjacent samples with the average value of that group. This process preserves the signal while rejecting noise, and can squeeze a few extra bits of resolution out of your converter. For example, in the presence of noise, an oversampling factor of four is typically equivalent to increasing the resolution of your converter by one bit, and a factor of sixteen is equivalent to two extra bits.
Normally, PicoScope sets up oversampling to get the best out of your oscilloscope so you don’t have to worry about the details, but there are some adjustments you can make if you need to. In the PSW.INI file installed in the program directory, you can add two parameters called MaxOversample and MaxScopeOversample. MaxOversample applies to the ADC-200 series of converters, and MaxScopeOversample applies to the PicoScope 2000 and 3000 Series. For example, you can boost the resolution of a PicoScope 3224 or 3424 from 12 bits to 16 bits, under suitable signal conditions, by adding the line:
You can use other oversampling factors in the range 1 to 256. It is best not to use a higher oversampling factor than necessary, because this can slow down the refresh rate of the PicoScope display and can sometimes lead to ‘aliasing’. There are more details in the reference manual included with your PicoScope software: click ‘Help’ and look for ‘initialisation settings’ and ‘aliasing’ in the index.
Finally, make sure that the 'Maximum samples per scope trace' setting in PicoScope under Settings | Options | Advanced is not too high. This setting multiplied by MaxScopeOversample must be less than the buffer size of the oscilloscope to enable PicoScope to oversample by the requested amount.
The PicoScope 2104 and 2105 scope–in–a–probe PC Oscilloscopes are attracting a lot of attention in the electronics press. Alex Mendelsohn has just written an independent review for eeProductCenter, in which he describes the new PC Oscilloscopes in detail and points out numerous advantages, such as their low cost, ergonomic design and fast equivalent-time sampling.
New Real-Life Diagnostics article: “Misfire Most Severe”
In this month’s article in the Real–Life Diagnostics series, Nick Hibberd of Hibtech recounts how he solved the case of a misfire in a high–performance engine that was blowing smoke. The trouble code pointed to an injector problem, but Nick needed an automotive oscilloscope to find the exact, and surprisingly simple, cause of the fault.
New reference waveform: crankshaft and camshaft
This month we have added a new reference waveform to our library: a dual-trace crankshaft and camshaft waveform from a Fiat Coupe 2.0. The crankshaft waveform shows an obvious problem, indicating a damaged sensor, flywheel or crankshaft.
Send us your waveforms!
We are grateful to you, our customers, for sending us your waveforms, and we encourage you to keep sending them, preferably as matching pairs of ‘before repair’ and ‘after repair’ examples. If you wish, we will identify you as the author of any waveforms that we publish.
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