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Medi-Stim, Inc.
217 Industrial Court
Wabasha, MN 55981

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Product Support F.A.Q. Ordering Info About Us

Frequently Used ModalitiesElectrode Placement ChartElectrotherapy GlossaryAbout Waveforms

About Waveforms

Parts of a Waveform

A waveform is the visual shape of a pulsed electrical current. It includes the following components:

Amplitude: The magnitude or intensity of the current. Measured in peak mA.

Phase Duration: The time elapsed from the beginning to the termination of one phase of a pulse. Measured in microseconds (µsec.)

Pulse Duration: (Pulse Width) The time elapsed from the beginning to the end of all phases plus the interphase interval within one pulse. Measured in microseconds (µsec.)

Interphase Interval: (Intrapulse Interval) The time between two successive components of pulse when no electrical activity occurs. Measured in microseconds (µsec.)

Interpulse Interval: The time between two successive pulses.

Pulse Rate: The number of pulses per measure of time (one second). Also referred to as frequency. Measured in hertz (Hz).

Symmetrical Biphasic Asymmetrical Biphasic
Symmetrical Biphasic Asymmetrical Biphasic


Most TENS units utilize an asymmetrical biphasic waveform. With biphasic waveforms there is not the problem of producing a net skin charge which could lead to possible burns.

Asymmetrical biphasic waveforms have two phases, an active phase and a balancing (usually passive) phase. In the active phase the positive going current travels through the positive electrode into the tissue, and during the balancing phase the current returns out the negative electrode. A mirror image of the waveform at the positive electrode occurs at the negative electrode.

Neurons depolarize more readily to negative current.



Types of Waveforms

Type Clinical Uses Waveform
Monophasic Waveforms
Direct Current 4(DC) or Galvanic Iontophoresis, wound healing, denervated tissue Galvanic DC
Pulsed Galvanic or Interrupted DC Edema reduction, wound healing, innervated muscle contraction Interrupted DC
Interrupted DC2
Biphasic Waveforms
Symmetrical AC Pain suppression, innervated muscle contraction Symmetrical AC
Asymmetrical AC Pain suppression, innervated muscle contraction Asymmetrical AC
Triphasic Waveforms
Unbalanced Triphasic Edema reduction, pain suppression Unbalanced Triphasic

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