The PowerLab

This instrument is called an analogue to digital converter (A/D converter). It changes the continuous signals sent from the voltage clamp amplifier into digital signals that the computer can recognize.

The difference between analogue and digital here is the same as the difference between a cassette tape and a compact disc (CD). The tape has the music stored as continuous waves of sound - which is the was it is produced and the way out ears normally hear it. A CD is made of these recordings by converting these continuous waves into bits of information (1's and 0's) and then storing them. The CD player decodes this and converts it back to continuous waves so that we can understand it when it's played back.

In terms of electrophysiology, imagine that the event you're recording is an action potential that looks like this in analogue. This is a continuous wave of depolarization and repolarization.

Since computers have a hard time with continuous information this, it has to be broken down into individual points. Each of the red dots here represents one data point that's taken from the original signal.

This stream of individual points is sent to the computer which reads and displays this input, as seen at the right. If the distance between the points (which is determined by the sampling frequency) is small enough, you get a good representation of the original continuous data.

This is all you have to know about the PowerLab component of the system. There is an input from the current electrode that goes into channel one of the PowerLab and an input from the voltage electrode goes into channel 2. For the most part, you won't have to change this during an experiment.

Back to Recording Equipment page.