Hello,

Why My digital voltmeter counts and shows me several digits changing by time while I touch it by my hands?
My professor told me it's because our body has voltage??!

What about when it acts like an Antenna?

 

True.
A good digital voltmeter set to its lowest range can usually pick up the small electrical potential variations form place to place going through our skin when muscles are contracting and relaxing.
Try using two damp electrodes placed at different places on your arm and then flex different muscles. With a bit of testing and practice you can repeatedly and accurately raise, lower and reverse the polarity of the tiny voltages present on your skin.

Use an amplifier circuit to bring that voltage up high enough and you can use it to control simple circuits just with the correct muscle movements!

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"Your impossibility may just be my day to day routine." -- tcmtech

 

That sounds like too much work. Just eat a few tins of baked beans then point ya rear end towards a small wind genny. The only muscle used there is quite soothing after a few tins of baked beans.

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" The only way to avoid human error is to avoid the use of humans"

 

Thanks, So it is due to Muscles of human body right?

What about the ability of humans body to act as an antenna?

 

W.R.T electroman 1st post
I had also observed the same phenomena on my digital multimeter.I thought it is because each part of our body sends electric pulses to brain as a result of which we sense & perform.So is that voltage due to electric pulses??

 

W.R.T electroman 1st post
I had also observed the same phenomena on my digital multimeter.I thought it is because each part of our body sends electric pulses to brain as a result of which we sense & perform.So is that voltage due to electric pulses??

 

No, my understanding is that voltages you may read on your skin are from charges due to our body's capacitance. We store potentials on the surface of the skin and discharge them frequently. This can fluctuate due to humidity and environmental conditions. This is why solid state devices made with field effect technology are especially vulnerable to our touch and should be handled with ESD techniques. Tiny discharges of hundreds of volts can leave our body when we touch objects without us even being aware.

This is also why we have an effect on antennas, it is called capacitive coupling.

 

The body can act as an antenna since the body is conductive and any conductive material can be an antenna.

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Carl
Curmudgeon Elektroniker

 

The human body's capacitance is sometimes responsible for changes in electrical potential, but all points in space in the entire universe have electrical potential. If you had a meter sensitive enough, you could measure the voltage between two points in air. However, this voltage is usually so small that your run-of-the-mill meter can't even come close to detecting it.

To answer the OP directly:

Yes, the human body has voltage, and sometimes this voltage is measurable. The voltage generated by the flexing of muscles is sometimes measurable, as is the voltage generated by neurological processes. Even single cells in your body have a voltage, but that voltage is usually too small to show up on meters.

 

ke5 modern meters have input impedance of at least a megaohm, he could be reading real voltage.
Nerve impulses are chemically influences but electrical in overall nature.

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Yes, I know that digital meters have high input impedances. And I never said he wasn't reading real voltages. Why wouldn't the potentials present on the human body be real?

 

Not so much that it wasn't real, but that it wasn't from within the body. The human body has the potential to create voltages not just as a passive capacitive device, I thought you were saying that when you started the sentence with no. Especially considering that the electrical impulses to muscles are just that, chemically derived potential differences followed by current flow triggering cell reaction. Mind you the muscle reaction itself isn't directly actuating muscles but triggering them to actuate. I thought you were infering than any voltage read from the human body was of an external origin and we were merely passive components.

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Ah, I do not disagree with you that the human body creates its own voltages (micro and milli)...of course, we wouldn't be able to think or control or sense our tissues. But these are internally produced and the epidermal layer, when clean, has a resistance of at least 500 to millions of ohms.

The voltages you can read on your body with your electricians voltmeter are AC coupled voltages from power lines and all the AC sources surrounding us.

 

A run-of-the-mill fluke meter does a fine job of picking up voltages coupled to your skin from the surrounding environment.

 

AC coupled voltages read in DC mode?

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