Classified by machine function
According to the functions of the machine, the electrocardiograph can be divided into an ordinary electrocardiograph with graphic tracing (analog electrocardiograph) and an electrocardiograph with graphic tracing and analysis and diagnosis (digital intelligent electrocardiograph).
Classification by recorder
The recorder is the tracing element of the electrocardiograph. For analog electrocardiographs, the recorders used in the early days were mostly moving coil recorders with disc springs returning to zero torque. After the 1990s, position feedback recorders were mostly used. For a digital electrocardiograph, the recorder is a thermal or dot matrix printer.
1. Moving coil recorder: The structure principle of the moving coil recorder is a fixed magnetic circuit and a rotatable coil composed of magnetic steel. The output signal of the power amplifier of the electrocardiograph is added to the coil of the recorder, and a stylus is fixed on the coil. When there is an ECG signal output, the power amplifier outputs current to the coil, and the coil rotates. When the deflection angle of the coil is the same as the zero return torque of the disc spring, the deflection is stopped. In this way, the stylus driven by the coil traces the electrocardiogram waveform on the recording paper.
2. Position feedback recorder: The position feedback recorder is a recorder that does not require a mechanical return spring, and a special electronic circuit can play the role of a return spring. When the machine is powered off, the stylus of the position feedback recorder can be moved arbitrarily.
3. Dot matrix thermal recorder: The thermal recorder uses the semiconductor heating points sintered on the ceramic substrate to burn graphics and characters on the thermal paper that develops color when heated.
