Resolution enhance
What it does
Resolution enhance increases the effective vertical resolution of your waveforms at the expense of high-frequency detail. You can apply resolution enhancement individually to each of your captured waveforms.
The technique works when the signal contains a small amount of noise (typically noise is present in most normal waveforms) and uses a flat moving-average filter to smooth out the small steps that become visible when you try to view your waveforms with maximum (unenhanced) resolution.
How it can help you
Sometimes you only want to look at a small part of your waveform but, for other reasons, need to capture the waveform over a relatively large input range. In these situations, the smaller waveform part will be captured with a compromised resolution.
One example of this might be when you are capturing a Magneto-REsistive (MRE) wheel speed sensor output voltage, which consists of a small square wave waveform at a relatively high offset from zero volts: The offset is due to the supply voltage that powers the sensor and the square wave waveform is the output from the sensor. A problem with either the supply voltage or the sensor operation can cause an intermittent fault so you need to capture both parts in those cases, which means that the resolution available across the small square wave waveform will be reduced.
In these circumstances, you can use Resolution enhance to increase the effective resolution of your waveforms so you can see the smaller parts with more clarity.
How to use it
Click the Channel options control to open the Channel options panel for the waveform of interest. Then select the DSP tab to access and use the Resolution enhance control.
Select an effective number of bits equal to or greater than the resolution of your PicoScope Automotive oscilloscope.
The resolution enhancement value, e, changes the number of values, n, used in the technique’s moving-average filter algorithm (see the table below). The larger the number of values used, the larger the waveform’s required sampling rate. If the sample rate is too low, resolution enhancement will cause the following side effects:
- Widened and flattened impulses (spikes).
- Vertical edges, such as those of square waves, turned into straight-line slopes.
- Inversion of the signal, sometimes making it look as if the trigger point is on the wrong edge.
- A reduction in signal amplitude, or even a flat line, when there are not enough samples in the waveform.
The side-effects of resolution enhancement can be counteracted by reducing the level of enhancement, increasing the number of samples captured or changing the collection time. Trial and error is usually the best way to find the optimum resolution enhancement for your application.
The side-effects of resolution enhancement can be counteracted by reducing the level of enhancement, increasing the number of samples captured or changing the collection time. Trial and error is usually the best way to find the optimum resolution enhancement for your application.
| Resolution enhancement, e (bits) |
Number of moving average values, n |
| 0.5 |
2 |
| 1.0 |
4 |
| 1.5 |
8 |
| 2.0 |
16 |
| 2.5 |
32 |
| 3.0 |
64 |
| 3.5 |
128 |
| 4.0 |
256 |
Example
Your scope device is a PicoScope Automotive 4425A oscilloscope (resolution = 12 bits). You have selected an effective resolution of 14 bits. Therefore, the resolution enhancement is:
e = 14.0 – 12.0 = 2.0 bits
And the number of moving average values required to achieve this enhancement is:
n = 16 samples
The number of moving average values indicates the degree of the waveform filtering effect delivered by resolution enhancement.
In some operating modes, PicoScope may reduce the number of samples available in order to maintain performance.
