PicoScope 7 Automotive Scope School Part 1 – Introduction
by S Smith

The introduction of a PC based oscilloscopes revolutionized the automotive diagnostic process for technicians across the world. Combined with dual, high-resolution monitors, multiple scope channels, lightning speed capture rates, large sample memories, and an abundance of analysis features, the once “undiagnosable” issues can now be caught, displayed and shared for all to see. 
 
However, without intuitive software to complement the hidden potential of an oscilloscope, such an immense diagnostic tool is soon left to gather dust!
PicoScope 7 Automotive software has been designed from the ground up with ease of use in mind. Combined with our BNC or PicoBNC+ range of scopes, you can be assured of success when acquiring that first capture.

What is an oscilloscope? 

An oscilloscope will allow you to graph your chosen signal against time, allowing you to observe changes in the signal behaviour. For ease of use, PicoScope 7 Automotive has grid lines that divide the graph view into 10 divisions. The input signal level is displayed along the vertical axis, while the time is plotted along the horizontal axis
In the waveform below, we have used PicoScope 7 Automotive to capture and plot a camshaft position sensor signal (voltage) against time. 

Note how the measured signal over time changes between 5 V and 0 V and the entire capture time equates to 10 x 20 ms/div = 200 ms (0.2 of second).
 
The image above immediately highlights the power of an oscilloscope as we can now observe changes to the camshaft sensor signal under any running condition, a feature that is not available with a multimeter.

Acquiring that first capture 
Connecting the scope to the vehicle and acquiring a measurement does not have to be daunting or anything to fear. The initial connection is identical to that of connecting a multimeter, however, we now have the distinct advantage of visualising the signal over time. 

Taking the process “one step at a time”, PicoScope 7 Automotive has been designed to allow easy configuration of the scope channels by using a single Channel options button. 

Below you can see how we clicked on Channel A to open the Channel options menu for Channel A. 

Voltage setting 

As you would set the input range on your multimeter for the expected signal voltage, the same process applies to PicoScope. Click on the Channel options button to reveal the Channel options menu and select the desired vertical input range.

In the image below, we have chosen an input range of ±10 V from the Vertical tab in the Channel options menu for Channel A. The setting will now configure your scope to display any voltage that falls between +10 V and –10 V.

Note how each division on your vertical axis now has a value of 2 V and how 0 V appears in the centre of the graph view.

Probe setting (standard BNC probes) 

Following on from the Vertical tab in the Channel options menu, we then have the Probes tab. Selecting the correct probe is essential, as this informs PicoScope of the type of measurement you are about to take and amends the scope input scale and measurement units accordingly. The x1 probe is the standard option for the majority of voltage measurements and this is conveniently selected as the default probe. With the x1 probe selected, PicoScope sets the scale and unit values for voltage measurements. However, if you select the 30 A current clamp from the probe menu, PicoScope would adjust the scale and unit values to correctly display a current measurement (i.e., amps instead of volts).

Probe setting (PicoBNC+ probes) 

For owners of the 4x25A PicoBNC+ scopes, the probe setting could not be any easier as probe selection, configuration and auto-zeroing are taken care of automatically when you connect a PicoBNC+ probe to the scope.

In the image below, you can see that PicoScope has automatically detected that a PicoBNC+ 60 A current clamp has been connected to Channel A, and it has configured the probe options for that channel accordingly.   

Time setting

Selecting the time setting for a measurement with a conventional multimeter has never had to be considered. The value displayed on your meter screen is an average over a pre-set time. With PicoScope, we can specify the time that spans across the entire graph, which gives us a crystal-clear view of the ever-changing input signal regardless of the speed of change.
When clicking on the Time button the Timebase menu opens and you can select the time displayed across the graph view by using time per division units.

Below we have opted for 20 ms/div, which equates to 200 ms across the entire capture.

• Reducing the time base setting (e.g., 20 ms/div) will allow for easier detailed viewing of a single event such as one camshaft rotation in the graph view.
• Increasing the time base setting (e.g., 200 ms/div) will allow for detailed viewing of multiple events such as numerous camshaft rotations in the graph view.

Trigger setting

When capturing input signals that change rapidly over time, they will appear to shift or jitter about the graph. This makes them very difficult to view and analyse in real-time. To overcome this issue, we can introduce a set of “Trigger conditions” that have to be met before the signal is displayed in the graph view. This provides convenient means to stabilise the signal of interest.

While there are numerous trigger features and conditions available in PicoScope 7 Automotive, we will cover and describe the following options which you can access by clicking the Trigger button:  

• Auto Trigger Mode
• Simple Edge Type
• Trigger source
• Pre-trigger
• Trigger Threshold 
• Direction

Trigger Mode

The first trigger condition is the Trigger Mode and for this example, we will select Auto. Selecting Auto will force the scope to wait for the trigger conditions to be met before displaying the waveform on the screen. However, if the conditions are not met within a set time, PicoScope will display the waveform regardless. This is a great feature when using triggers for the first time, as it will allow the scope to display a waveform, even if you have set your trigger conditions outside the values for the signal being measured.

Trigger Type

The second trigger condition is the Trigger Type. Here we are asking the scope to trigger on a “Simple Edge” (a transition from high to low or low to high) present in our input signal. 

Trigger source

The third trigger condition surrounds the channel upon which you wish the trigger settings to be applied. In our example below, we have chosen Channel A as the Source for our trigger conditions.

Pre-trigger

The fourth condition refers to the Pre-trigger settings, i.e., where on the graph do you wish the trigger to be placed (left to right) specified as a percentage of the horizontal axis? Each division on the graph represents 10% and, in our example below, we have opted for a pre-trigger of 30 %. This setting will indicate the signal before the firing of the trigger when all the specified conditions have been met.

Trigger Threshold

The fifth trigger condition is the Threshold, i.e., the voltage level that has to be crossed before the input signal is displayed. Below we have opted for a threshold voltage of 2 V.

Trigger direction

The sixth and final condition is the Direction, i.e., do you want the trigger to capture the signal when it is increasing (Rising Edge) or decreasing (Falling Edge)? In the case of our square waveform below, we could use either of these options as we know our signal has both rising and falling edges.

To recap

In the image below, an auto-trigger mode has been applied, where PicoScope will wait for a simple edge signal present on our specified source (Channel A) to cross a threshold of 2 V in a rising direction at a pre-trigger point in the graph view of 30%. Since we selected the auto-trigger mode, PicoScope will display the waveform regardless if these trigger conditions are not met within approximately three seconds. 

PicoScope utilises a yellow trigger diamond in the graph view to denote the trigger type, pre-trigger and threshold settings. Please note that you can click and drag the trigger diamond to a new location in the graph view to edit the settings above. 
You now have a solid foundation to apply when setting up your scope to capture virtually any signal, but don’t worry if this all seems like information overload as help is at hand.

When you open PicoScope 7 Automotive, you will see our Automotive Guided test menu. In this menu, you can access over 150 specific tests focusing on components you may want to test. More importantly, the Guided tests will configure your PicoScope to capture your chosen signal, automatically taking care of all of the settings described above.

In addition to our Guided tests, the DON’T PANIC! button will guide you to a host of additional support material in the form of tutorials, case studies, videos and our incredibly useful “A to Z of PicoScope”.  
Should you wish to go at it alone, and set PicoScope manually, go ahead. However, if the waveform does not appear as expected, or worse still, does not appear at all, further help is at hand. Clicking the Auto setup button will automatically configure the scope settings to capture the signal under test.

Alternatively, you can click on the More button in the left-hand tool panel and then the Reset configuration button. This will return the PicoScope 7 Automotive software to the default scope settings (more on this in Scope School part 2).