A Basic Biomedical Recording System

Recorders provide permanent visual trace or record of an applied electrical signal. The most basic electronic recording system consists of 3 important components:

• Electrodes/Transducer
• Signal conditioner
• Writing system

The electrode picks up the bioelectric potentials whereas the transducer converts the physiological signal to be measured into a usable electrical output.

The signal conditioner converts the output of the electrode/transducer into an electrical quantity suitable for operating the writing system.

The writing system provides a visible graphic representation of the quantity of the physiological variable of interest.

In medical recorders, the signal conditioner usually consists of a preamplifier and the main amplifier. Both of these amplifiers must satisfy specific operation requirements such as input impedance, gain and frequency response characteristics for an effective reproduction of the input signal.

To make the signal from any transducer compatible with the input signal required for the driver amplifier of the display or recording system, it is usual to arrange to normalize the electrical signals produced by each transducer. This is done in the signal conditioner which adjusts its output to a common signal level e.g. one volt. The necessary adjustments of gain and frequency response are provided by the signal conditioners. This means that, it is possible to interchange the signal conditions to record any one of the physical or bioelectric events on the same writing channel.

You can also read: The Basics of a Biomedical Instrumentation System

The writing systems which are available in many forms constitute the key portion of the recording instrument. Examples of commonly used writing system include: The Inkjet recorder, Galvanometer type pen recorder, Potentiometric recorder, etc.