Math channels

What it does

You can use Math channels to calculate new waveforms from your captured waveforms and gain more insight into your test results.

You are free to create as many Math channels as you need and each one can be the result of one or more operations performed on one or more of your original waveforms.

Math channels waveforms are created after each waveform buffer (the part of the oscilloscope’s memory that stores a chunk of data) has been filled; you will not see them until after the buffer is full.

Example Math channels operations are:

  • Invert a waveform.
  • Add, subtract, multiply or divide waveforms.
  • Transform a waveform to a running estimate of its frequency.
  • Calculate a running estimate of a waveform’s positive or negative duty cycle.
  • Convert an analog or digital Crankshaft Position (CKP) sensor output waveform to a running estimate of crank speed (RPM).
  • Filter your waveforms using highpass, lowpass, bandstop and bandpass filters.
  • Apply many other scientific and trigonometric functions to your waveforms.

You can adjust the settings (parameters) related to each operation to suit your needs.

You can also create custom Math channels that perform a selected set of operations, with predefined settings (parameters), that might be specific to your typical applications.

How it can help you

Sometimes you cannot directly measure the physical quantity you are interested in. Instead, you can measure related quantities and use Math channels to calculate them.

A typical example might be circuit resistance and power consumption where you could measure the circuit voltage on one oscilloscope channel (A), its current on another (B) and combine them both in two separate Math channels: A / B gives you the circuit resistance and A * B its power.

Another example is an engine’s crank speed, which can be calculated from a measurement of a CKP sensor’s output voltage using the Math channels’ Crank operation.

With its extensive set of processing tools, Math channels allow you to crack open the insights hidden in your waveforms and fix diagnostic problems that are not easily solved using other tools or processes.

How to use it

Select Math channels. Then select a predefined channel or make your own to create a new onscreen waveform derived from your measured waveform.

The example below shows you how to create a waveform that shows the running negative duty cycle (equivalent to the Pulse Width Modulation percentage) for a Common Rail Diesel Quantity Control Valve (also known as an Inlet Metering Valve), calculated from the control circuit voltage (on Channel A).

An animation showing how to use the Math channel feature in PicoScope 7 Automotive