Answer on how to measure intensity value with oscilloscope

Question

Since the oscilloscope only represents voltage, we know that a formula is applied to find the intensity, but it does not match that of the stimulator.

Can you refresh us on the concepts and the formula in case we make mistakes?

Answer

The formula is:

V / R = I

The voltage value in the intensity wave must be read and the intensity resistance measured with a multimeter (without current passing). For this, the load resistance that simulates the patient does not count.

A cause of the possible failure can be found in an incorrect value of R or also in the value of V and where it is taken from.

I suggest that you do the measurement with the galvanic current to compare it with that of the stimulator. If this causes failure, something is wrong with the stimulator's measurement system (as long as 5% error is exceeded). If the result is acceptable with galvanic, proceed to test with a perfect square current with pulse times of about 5 ms and rests of about 5 ms; They can be other time values, but the same for pulse and for rest. The stimulator in CC.

Read the voltage value at the plateau of the quadrangular pulse and divide by the current resistance (with its real value); the result should match that of the stimulator (with a certain margin of error).

If the stimulator gives a value half the result of the formula, the stimulator does not read the peak intensity, but it does read the effective intensity.

This does not normally occur in standard and professional stimulators, as they are designed to measure peak intensity in pulses (especially scanning currents). Unless the stimulator indicates in some way, what type of intensity it signals.

If with the square waves everything was correct, it can be repeated with triangular and sinusoidal waves; With these waves, depending on the height at which the voltage values are taken, the intensity will also correspond to that height in the wave.

I suggest you see in the book PRÁCTICAS DE ELECTROTERAPIA, in the 2nd chapter, the epigraph HOW TO MEASURE THE INTENSITY WAVE IN A SIMPLE WAY..

I also suggest you read these two links:

http://electroterapia.com/onda-de-intensidad.php

http://www.iontoforesis.com/medidor-onda-intensidad.php

With these three references, you will surely end up mastering the subject and will be able to answer any questions about it.

You will already tell me about the results obtained, because I am also interested in knowing about your conclusions and findings.

Posted on 06/03/2021

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