Rise/Fall time in the PicoScope Software

Rise/Fall time trigger, can also be referred to as Slope or Slew rate trigger. This trigger measures the time the signal takes to transition between two voltage thresholds: from a lower threshold to an upper threshold in the case of rise time, or the opposite in the case of fall time.

The scope triggers when the measured transition time meets a user-specified time condition: greater than, less than, inside a range or outside a range of times. Unlike window pulse width trigger, rise/fall-time trigger allows you to trigger specifically on rising edges or on falling edges which meet a time condition. This can be useful if the expected slew rate of rising and falling edges is different in your system. 

<< All advanced trigger modes

Slow rising edge example

In this example the rise time trigger was set to trigger on rising edges which transitioned from -500 mV to +500 mV in greater than 100 ns. It ignored the rising edges which were faster than 100 ns, and the falling edges regardless of their rate, and triggered only on the slower rising edge.

How to set up Rise/Fall time trigger

In this example we’re testing a square wave signal with varying, exaggerated rise times provided by our Mixed Signal Oscilloscope Training and Demo Board. The standard rise time for this signal is around 170 μs from 300 mV to 3 V.

To find a long rise slope, we’ll switch to the Rise/Fall time trigger type in the trigger lozenge by clicking .

Once the trigger mode is changed we’ll define our constraints. First, we’ll set our voltage thresholds, this tells the PicoScope what the start and end rise time will be. As we’re looking for the slope between 0.3 and 3 V we’ll use those as our threshold. 

We’ll then keep the Time Condition as Greater than and set the Time 1 to 180 μs. Once the PicoScope is running again, we can see it locks onto a rise time which, using a rise time automated measurement, comes to around 245 μs.

This trigger measures the time the signal takes to transition between two voltage thresholds

Expanding on this, we can capture a smaller rise time or fall times by changing the trigger configuration. Using the same demo signal, try switching the Time Condition to Less than to capture smaller rise times. Or switch the Direction to Fall time to capture the falling edge of the demo signal. 


Compatability

The rise/fall time trigger type is only avaliable from scopes with the following designation:

2000 Series - designations 'B' and onwards
3000 Series - designations 'D' and onwards
4000 Series - designations 'A' and onwards
5000 Series - designations 'D' and onwards
6000 Series - designations 'E' and onwards