Persistence is a graphing mode that overlays incoming waveforms on top of each other so that you can see how or whether they with time.
Persistence mode groups all the waveforms into one line. If you want to be able to separate them out again afterwards, take a look at memory buffer overlays too.
How it can help you #
Persistence is useful for capturing and analyzing events that occur infrequently or for viewing the behavior of signals over an extended period. It can be used for capturing glitches in repetitive signals that typically remain fixed during normal operation. i.e. Fixed duty or frequency actuator control signals.
How to use it #
Click on the More button located in the side panel and select the Instrument button.
With the Instruments dialog open, select Persistence.
Select Persistence mode whilst using a Repeat Simple Edge Trigger on channel A to stabilize the incoming square wave signal.
The default configuration for Persistence mode utilizes Fast and Scatter which draws sample points as unconnected dots. For more information, please refer to Persistence Controls.
Select the Persistence lozenge, the newly opened Persistence tab will reveal the configuration options: Fast, Time and Frequency.
In this example we have modified the default Persistence controls as follows:
Persistence type Frequency
Saturation 50%
Decay intensity 0%
Line drawing Phosphor
For more information please refer to Persistence Controls.
We have introduced a fault condition which has been captured and highlighted using the colour blue. The color red is used for the most frequent data whilst the least frequent data is represented successively by the colors yellow and blue.
Using the Zoom feature, we can see how the repetitive incoming signal has been interrupted, resulting in a phase shift.
Persistence Controls #
Selecting the Persistence lozenge will reveal the Persistence configuration, which includes Timebase and Persistence settings. In the example below, we have the time-based setting. Please note, the maximum time-based setting for Persistence mode is 20 ms/div.
Clicking on the Persistence tab, followed by the Information button, will provide an explanation of the Persistence types.
Persistence types #
Fast: Comes with simplified display options to enable the fastest possible update rates
Time: Uses color intensity to indicate the age of the waveform data. The latest data is drawn at full intensity in the selected color for that channel, with older data being represented by paler shades of the same color
Frequency: Uses a range of colors to indicate the frequency of waveform data. Red is used for the most frequent data, and less frequent data is represented successively by yellow and blue.
Please note: The Frequency option has been used as an example in this article.
Fast persistence #
This is the default persistence type, providing a reduced configuration and simplified display options to enable the fastest possible update rate. The PicoScope draws this data on the graph using a color-coded scale to indicate the densest parts of the waveform in red and the infrequent glitches and waveforms in blue.
This mode is ideal for quickly detecting rare events and glitches hidden in otherwise repetitive waveforms that may not be caught using the standard scope modes.
Frequency persistence #
Similar to the fast persistence type, Frequency mode uses a range of colors to indicate the frequency of waveform data. Red signifying the most frequent data, yellow to blue representing less frequent data.
Frequency persistence provides more configuration than fast mode, allowing the user to change the Saturation and Decay intensity to adjust the visibility of the least frequent waveform data.
This mode is useful for capturing frequent glitches and spikes in a visual format.
Time persistence #
Dissimilar to Fast and Persistence mode, Time uses color intensity to indicate the age of the waveform data. The latest data is drawn at full Saturation in the selected color for that channel, with older data being represented by paler shades of the same color.
This mode allows the user to adjust the Decay time of the oldest waveform data, in seconds. If changed to Infinite, the data will not decay. Alongside this unique setting, Time persistence also features configuration to change the Saturation.
Line drawing mode #
In Time and Frequency persistence modes, the line drawing mode can be adjusted between Phosphor, Constant or Scatter. These modes change how a line is drawn between samples that are adjacent in time.
Phosphor: Joins each pair of sample points with a line whose intensity varies inversely with the slew rate. Emulating a traditional Phosphor display.
Constant: Joins each pair of sample points with a line uniform in color.
Scatter: Draws sample points as unconnected dots, providing the user with raw data points.