# Maths is cool - part 5by Steve Smith

The Invert option is already a built-in math channel that allows you to invert Channel A or B should it be necessary for improved analysis.

Invert built-in

This is fine if the channel you wish to invert is Channel A or B, but if you want to invert Channel C or D?

The following is a typical example where I have the current clamp (on Channel C) installed in the wrong orientation for the current flow! How often doesn’t that happen?

I know it’s a 50/50 guess but for some reason, 90% of the time I have the current clamp the wrong way round.

Incorrect current clamp orientation

Placing the minus symbol (-) in front of any channel letter will invert the relevant channel. By using the formula –(C) we can invert Channel C to read the current in the correct “positive” direction.

Inert formula

Here is the math channel –(C), now with the current flow displayed in the correct orientation.

Math channel applied

While the formula is straight forward, it can be also be applied within other formulas to reverse the value.

Negative duty cycle is a typical example where the formula “duty(B)” would present the positive duty cycle of the signal on Channel B but “duty(-B)” reveals the more typical negative duty for our applications. This forum topic covers negative duty.

This forum post contains a number of negative duty cycle math channels available for you to download.