alpha2cen Posted January 16, 2011 Share Posted January 16, 2011 (edited) Is it possible to measure very very little current, i.c., 10 electrons per second? We can use amperemeter to measure ampere . But how can we measure very small ampere. I think this instrument might be very useful to measure bio-electrical signal and nano-pore DNA sequencing. Edited January 16, 2011 by alpha2cen Link to comment Share on other sites More sharing options...
John Cuthber Posted January 16, 2011 Share Posted January 16, 2011 Hypothetically, in ideal conditions you can measure currents that small. But it's not easy. http://www.tmworld.com/article/319701-Femtoamp_fA_measurements.php It will only work if the currents carry on for a reasonable length of time. Link to comment Share on other sites More sharing options...
alpha2cen Posted January 17, 2011 Author Share Posted January 17, 2011 Thank you for good answering. But it is useful for big currunt 1x10-15A. How about this method? Electric charge storage an emitting method. In the middle of the circuit we make some device for storage electric charge. First, few minute we save the electric charge, and emitt the saved charge. At this time we measure the current, and devide the current by the saving time. Any good opinion? Link to comment Share on other sites More sharing options...
lemur Posted January 17, 2011 Share Posted January 17, 2011 Why do you think current can be measured in electrons/second? Isn't electricity a wave that travels through electrons in a conductor as its medium? I think what you should be asking is what is the minimum amount of energy that would need to be added to a conductor to create such a wave. Is it a plank-constant that can cause a ripple through a gold wire or is more energy needed (I assume more is needed but I don't know how much or why). I think each material should have a minimum energy-wave that is related to its atomic structure, but that is just a guess. Link to comment Share on other sites More sharing options...
Xittenn Posted January 17, 2011 Share Posted January 17, 2011 Most bio-electric signals are in the form of ions not electrons as I recall :/ Link to comment Share on other sites More sharing options...
lemur Posted January 17, 2011 Share Posted January 17, 2011 Most bio-electric signals are in the form of ions not electrons as I recall :/ Meaning the ionization of a particle is transmitted as a wave through subsequent particles? Did someone else mention nerves or did you just decide to frame the issue in terms of them? Link to comment Share on other sites More sharing options...
alpha2cen Posted January 17, 2011 Author Share Posted January 17, 2011 Why do you think current can be measured in electrons/second? Isn't electricity a wave that travels through electrons in a conductor as its medium? I think what you should be asking is what is the minimum amount of energy that would need to be added to a conductor to create such a wave. Is it a plank-constant that can cause a ripple through a gold wire or is more energy needed (I assume more is needed but I don't know how much or why). I think each material should have a minimum energy-wave that is related to its atomic structure, but that is just a guess. 1A=coulomb/second, coulomb= electron number. Electron current is not different electromagnetic wave flow. Electron current is very slow in a conductor, but electromagnetic flow is very fast , it's speed is the same as light speed. Link to comment Share on other sites More sharing options...
lemur Posted January 17, 2011 Share Posted January 17, 2011 1A=coulomb/second, coulomb= electron number. Electron current is not different electromagnetic wave flow. Electron current is very slow in a conductor, but electromagnetic flow is very fast , it's speed is the same as light speed. Please explain coulomb/second. You are not differentiating between atomic electrons and waves that travel as current through the conductor? Do you distinguish between water molecules and ocean waves? Between air molecules and sound waves? Are these flawed analogies? If so, why? Link to comment Share on other sites More sharing options...
alpha2cen Posted January 17, 2011 Author Share Posted January 17, 2011 Please explain coulomb/second. You are not differentiating between atomic electrons and waves that travel as current through the conductor? Do you distinguish between water molecules and ocean waves? Between air molecules and sound waves? Are these flawed analogies? If so, why? Let us take a look this site. http://www.slidefinder.net/e/electriccurrent/13274269 slide 6 It will be sufficient for your inquire. Link to comment Share on other sites More sharing options...
lemur Posted January 17, 2011 Share Posted January 17, 2011 Let us take a look this site. http://www.slidefind...urrent/13274269 slide 6 It will be sufficient for your inquire. Does "electron drift speed" refer to the speed of the current moving through the wire or something else? Link to comment Share on other sites More sharing options...
alpha2cen Posted January 17, 2011 Author Share Posted January 17, 2011 Real electron moving speed at the atom is not so slow, but it's movement through the conductor is very slow, i.e., conductor direction moving speed is slow. My question is "Can we storage very few electrons(60,000 ~ 100,000) accurately in the any device?" Link to comment Share on other sites More sharing options...
TonyMcC Posted January 17, 2011 Share Posted January 17, 2011 Nobody is mentioning thermal noise. I feel this will swamp any current that can be counted as a small number of electrons per second. It is cerainly a problem with very sensitive equipment such as radar receivers. Link to comment Share on other sites More sharing options...
ewmon Posted January 17, 2011 Share Posted January 17, 2011 Very little in life is actually measured directly, and I doubt that any method or device exists that can actually count the passage of ten electrons over the course of one second. Instead, a device can accumulate/integrate the current over a period of time and then measure this captured charge. Or an amplifying device can amplify/cascade this current/electrons, and then, measure this magnified current/charge through more conventional means and scale it to the original current. For example, this addresses some of the OP's criteria: Recent improvements in CCD design have greatly diminished dark noise to negligible levels and reduced their contribution to total read-out noise to less than 10 electrons per pixel at room temperatures. ... Some room temperature cameras may have such a low dark signal that it can be ignored for integration periods of a second or less. CCD Sensitivity and Noise Link to comment Share on other sites More sharing options...
TonyMcC Posted January 17, 2011 Share Posted January 17, 2011 In general amplifiers also amplify the input noise as well as the wanted input. Worse than that, they introduce extra noise from their own circuitry. This results in the signal/noise ratio at the output being worse than the input. Because of its random nature it is difficult to completely cancel noise effects. I'm not too sure whether today's technology can cope with this at such low levels of current. Link to comment Share on other sites More sharing options...
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