Medical Device Simulators

ESU

Ideal electrical relationships in electrosurgical waveforms and electrode contact area.

Module 01

Waveform & power

Ideal load resistance500 ΩContinuous sine peak200 VPacket duty cycle30%Energy interval2.0 s

Electrical calculation example: 500 kHz. The display uses a normalized, slow-motion timeline and is not shown at the calculation frequency.

Why these controls?

These sliders are the electrical inputs of the two ideal waveforms. Move them to see how RMS voltage, average power P = V²RMS/R and energy E = P·t respond — and how the duty cycle bridges the continuous and packeted cases.

Continuous sine

Peak: 200.0 V
RMS: 141.4 V
Avg. power: 40.00 W
Energy: 80.00 J

Packeted sine

Peak: 200.0 V
RMS: 77.5 V
Avg. power: 12.00 W
Energy: 24.00 J

Continuous sinePacketed sine

Model equations

Continuous: V_RMS = V_peak / √2

Packeted: V_RMS = V_peak √(D/2)

Power: P_avg = V_RMS² / R

Energy: E = P_avg · t

The curves are idealized sinusoids, not exact waveforms for any real cut or coagulation mode. Equal average power does not guarantee equal tissue effect.

Module 02

Electrode area & current density

Total RMS current300 mAContact area5.0 cm²

Average current density

60.0 mA/cm²

J = I / A = 300 mA / 5.0 cm²

If the area is halved to 2.50 cm², J doubles to 120.0 mA/cm².

Why these controls?

Current and electrode area decide current density J = I/A. Move them to see why the same current becomes a much higher density on a small electrode — the principle behind large dispersive return pads.

Conceptual current-path schematic only — not an electric-field solution and not to scale.