Automated measurements

PicoScope 7 provides many built-in, pre-defined measurements that can be applied to waveforms displayed on the graph. Advanced DSP technology ensues that the measurements are made with high accuracy and repeatability. 

Furthermore, if the DUT waveform characteristics change over time, the measurements track and display current results based on the live waveform. 

Statistics can be displayed to show Average, Mean, Maximum, Minimum and Standard Deviation values for the duration of a test. 

Advanced measurement features:

In addition to the basic measurements, the PicoScope software also provides Advanced measurement tools detailed below.

Measurements Logging: results can be recorded to a file over a defined period of time or number of waveform captures. The results log can be used to characterize circuit performance over medium or long duration tests - useful for evaluating circuit drift due to thermal and other effects. Also can be used to check device functionality against an externally controlled variable such as supply voltage etc.

Measurements limits & Actions: can be employed to do something (Beep/stop the capture/run an executable file etc.) if a measurement result violates a limit preset by the user. Unattended tests can be built and executed from within PicoScope 7 using Actions.

This article describes the factors that are common to these measurements, e.g. where to find them in PicoScope 7, how to configure them, etc.
 

Quick-Start

Measurements can be added with the 4 following steps.

1. Open Add Measurements panel
2. Select Source channel
3. Select Measurement to view
4. Configure the measurement in the settings panel

For more detail on the avaliable measurements and each step, read the full article below.

Available measurements

The measurements that are available are dependent on the Mode in which the scope is selected to operate in, Scope mode or Spectrum mode. Below is a list of all available measurements for each mode. Some of the measurements have an associated A to Z article in which you can find a detailed description of the measurement, screenshots, what it measures, how the measurement is calculated etc. Click the link to access the article. Some of the articles cover more than one measurement.

Scope mode

For Scope mode, the avaiable measurements are grouped into three categories, Amplitude, Time and Multi-Channel.

Spectrum mode

For Spectrum mode, the available measurements are in a single Spectrum catagory.

Spectrum

1. Amplitude at Peak
2. Frequency at Peak
3. Intermodulation Distortion (IMD)
4. Signal to Noise ratio (SNR)
5. Signal + Noise + Distortion to Signal ratio (SINAD)
6. Spurious Free Dynamic Range (SFDR)
7. Total Harmonic Distortion % (THD %)
8. Total Harmonic Distortion dB (THD dB)
9. Total Harmonic Distortion + Noise (THD+N)
10. Total Power

Setup and configuration

All the measurements can be found on the Add Measurements options panel. This panel is opened with the Measurements button, found under the channels or in the More... panel.

Once the Add Measurements options panel is open, all the measurements available for the current mode will be shown arranged into the appropriate categories.
Here are the measurements available for the Scope mode, arranged into Amplitude, Time and Multi-Channel categories.

The categories can be collapsed with the  button and expanded with the  button. By default, the categories are shown expanded.

To add a measurement, first select the Source channel the measurement should be applied to. This can be changed later if required, once the measurement has been added.

The Source options are the channels available for the connected device, typically A-D for a 4 channel device. Channels that are turned off are shown greyed out as these channels cannot be selected.

Once a channel is selected, select one or more measurements by clicking a measurement in the list.
 

Here are the measurements available for the Spectrum mode, arranged into just the single Spectrum category.

Adding a measurement in Spectrum mode is the same as in Scope mode, select your channel followed by your selected measurements.
 

Using the measurement

When the measurement is selected, if this is the first measurement to be added, a new Measurements panel will be created under the graph and the measurement will be automatically added to the panel. If the Measurements panel already exists then the selected measurement will just be added to it.

The measurement lozenge which is added to the Measurements panel shows the current measurement value as the most prominent piece of data.

Additional statistics data are shown on the right-hand side of the lozenge and comprise the following:

Min - The Minimum value measured.

Max - The Maximum value measured.

x̄ - Mean value measured.

σ - Standard deviation from the mean.

n - Number of buffers measured*.

On the left-hand side of the measurement lozenge is an icon depicting the type of measurement, together with a title for the measurement.

On the right-hand edge of the lozenge is a Delete button, click this to remove the measurement. If this is the last one in the Measurements panel, the panel will automatically be closed.

There is a settings cog icon, click this (or any white space inside the lozenge) to open a Settings popup window containing configurable settings appropriate to the measurement type.

Separate to the lozenges, inside the Measurements panel, is a lozenge size selector and a Reset button, click this to reset all values in all measurements.

The Size selector is used to select Small, Medium or Large style lozenges and can be used to adjust the size to find the best fit for the lozenges within the Measurements panel. There is also a splitter bar area between the graph and the Measurements panel which can be dragged up and down to resize the panel height. To accommodate a high number of measurements, the panel can even be dragged out into its own re-sizable window by dragging the Measurements panel in the top centre of the panel.

The data shown in the lozenges varies depending on the size selected. The Medium size shown above is the default size and shows the most data. Both Small and Large sizes only show the current value.

*The default behaviour is to calculate measurements over the span of a buffer. Whilst this also applies to cyclic measurements, the value is an average of the cycle calculated values. The section the measurement is being calculated over can be modified, by the graph section option, which for example can constrain the measurement to a single cycle.

Scope measurement settings

To display the settings applied to a given measurement, click either the cog or anywhere inside the lozenge. The popup shown contains the source(s) the measurement is against and the current settings.
The following popup screenshots cover all the Measurement settings available:

This first popup provides the settings which are common to most of the Scope measurements. Cycle at ruler 1, Cycle at ruler 2 and Cycle at trigger are only available for certain measurements.
Source - the channel to be measured.
Graph section - offers up to five options for targeting different sections of the graph.
Whole trace - measure the whole trace.
Between rulers - measure the section that lies between the time rulers.
Cycle at ruler 1 - measure just the  waveform cycle found at ruler 1.
Cycle at ruler 2 - measure just the waveform cycle found at ruler 2.
Cycle at trigger - measure just the waveform cycle found at the trigger point.
 

Note: You can identify which is Ruler 1 and Ruler 2 using the Rulers popup visible on the graph.

This popup provides a Threshold setting.
Threshold - Select the upper and lower threshold points to be either at the 80 and 20 % points of the signal range or at the 90 & 10% points of the signal range. The default is 80/20%.

This popup provides a variation on the Threshold setting plus an additional Hysteresis setting.
Threshold - Set to Use Signal rulers to set the upper and lower threshold manually with the rulers.
Hysteresis - Sets a hysteresis around the threshold value.
 

This popup provides a 2nd signal source selector for Multi-Channel Measurements (Delay and Phase). This screenshot shows the settings for the Delay measurement which measures the time delay between the two signals.
Source 2 - Select the 2nd source signal.

This screenshot shows the settings for the Phase measurement which measures the phase difference between the two signals.
Output Range - Use this to map the output to a range of 1 or 2 cycles measured in degrees, radians or as a percentage (%).
 

Spectrum measurement settings

The following screenshots show the different Settings popup windows available for Spectrum measurements:
 

Source - the channel to be measured.

Graph section - Defines the graph section constraint for a measurement. This is effectively the analysis window of the measurement.
The options available will depend on the spectrum measurement being configured. Measurements such as Amplitude at Peak, allow measurements to be taken “At Peak”, meaning the peak with the greatest magnitude across the whole trace. “Peak nearest ruler x”, is the peak detected nearest the ruler positioned by the user.
 

Spectrum Peak Span - This allows for more control over the measurement, by defining how many bins will be evaluated around fundamental/carrier reference (which will be the highest peak).

Highest harmonic - Some spectrum measurements, for example THD, calculate values using a fundamental frequency and its harmonics. This field selects the highest harmonic to be used for these calculations. For example, when the Highest harmonic is set to Third, only the second and third harmonics will be considered for THD calculations.

Harmonic search range - This option is only available on a subset of spectrum measurements. Similar to the “Spectrum Peak Span”, this option defines the number of bins to search within. However, this range is around each of the identified harmonics.
 

Measurements logging 

PicoScope 7 allows results of measurements to be recorded to a file for later analysis. The resulting log can be used to characterize the performance of a circuit over medium or long duration tests - such as when evaluating drift due to thermal and other effects, or can be used to check functionality against an externally controlled variable such as supply voltage etc.

The maximum number of rows recorded is limited by the user set constraints or disk capacity.

Setup and configuration

To set up measurements logging

1. Open the Measurements panel
2. Select the Logging tab
3. Choose a File name and location for the results file
4. Optionally choose the Time or number of Captures to be recorded
5. Switch Logging On. Note the red dot that appears in the Measurements lozenge(s) to indicate that results are being recorded.

Settings overview

Logging

Enable or disable the logging of measurements. When disabled, no recordings will be taken. If enabled, then logging will begin during the next capture if possible.

Logging will not begin if the target disk is full or if user permissions are invalid for writing to that location.

Logging will end when either a predetermined condition is hit (see below), a disk error has occurred or the capture stops.

File name

Choose the filename and location to be used for measurements. The text field can be used to amend the name for the file. The button can be used to display a file picker and choose the name and location. A small border will be displayed if the chosen name is invalid.

Stop logging at

The following settings allow logging to be automatically disabled when a predetermined condition is hit.

Time - Logging will stop on the first capture after the specified time has elapsed. This time is recorded from the operating system time so is limited by the precision of the system clock. The maximum time allowable is 1 week.

Captures - Logging will stop after the given number of waveforms have been captured. Up to 100,000 waveforms can be specified.

Localisation

Datetime formats, numeric and list separator characters are all retrieved according to the operating system settings. Datetime format in use will also be output and displayed as part of the timestamp column header.

Measurement limits and Actions

PicoScope 7 offers Pass/Failure limits for any measurement. This will give a visual indication within the measurement lozenge whenever the signal goes above and/or below a specified value.

Pass/Failure limits can be combined with Actions to immediately alert the user or utilise other Actions when a measurement threshold has been exceeded, above and/or below set limits.
Actions include:

• Stop the capture
• Save waveform to disk
• Play a sound
• Trigger signal generator
• Run an external application or script

For example, the instant a measurement falls out of specification, measurement pass/failure limits utilise Actions to save the waveform file and trigger a debugger so that circuit failures can be correlated with specific points of program activity. This automation can also be used to streamline production testing activities, saving valuable time.

Finally, PicoScope 7 gives the option to filter captured waveforms within the waveform navigator to only show waveforms that have either passed or failed the specified measurement limits.

Setup and configuration

To set up Measurement Pass/Failure limits:

1.  Open Add Measurements panel
2. Add a desired measurement
3. Within the added measurement settings popup, enable either an upper limit, a lower limit or both:
   1. For an upper limit, specify a threshold value for the failure condition, which will occur whenever a waveform is captured that causes the measurement value to go above the specified value
   2. For a lower limit, specify a threshold value for the failure condition, which will occur whenever a waveform is captured that causes the measurement value to go below the specified value.

It’s then possible to select Actions on failures to automatically create a new Action which will be set to run whenever a measurement limit failure event is encountered. See Actions for how to set up automated actions based on set events for PicoScope 7.

Once data has been captured with measurement pass/failures applied, pressing Show failed waveforms will open the waveform navigator directly showing only the waveforms that have failed the specified limit thresholds. Only displaying the passing waveforms is also possible by using the dropdown control within the waveform navigator options panel.