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Reducing noise in oscilloscope measurements using PicoScope 5
For many measurement applications, noise is a big concern. A typical example in the automotive field is measuring injector current using a current clamp. The signals from the current clamp are only a few mV in amplitude, yet nearby are ignition signals of many kV.
The best way to minimize noise is to try to eliminate it at source, in the above example keep the current clamp as far away from ignition components as practical and ensure all connecting leads are screened.
Physical precautions as described above will help minimise noise pickup, simple software filtering can often be used to further reduce its effects.
PicoScope oscilloscope software has several display modes that can be used to reduce noise pickup, the differences between these modes are described below and can be selected from the settings | options menu:
Current (Unfiltered)
This is the default display mode, it takes all the data captured by the oscilloscope and maps it onto the PC monitor using a min/max algorithm. This ensures any fast transients are displayed, but will also act to highlight any high frequency noise.
Current (Filtered)
This mode applies a simple low pass filter to remove high frequency noise from the oscilloscope display. This mode would be ideal for the automotive application described.
Average
This mode build up an average trace based on all cycles captured. This is useful for removing random noise from repetitive signals.
Min, Max and Average
This displays this displays a shaded area showing the minimum and maximum of all cycles captured. In addition it displays the average trace as well. As with the average mode, noise is removed from repetitive signals, in addition the shaded area gives an indication of how noisy the signal is.
Article: KB-173
12 Oct 2007
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