conversion question
conversion question
(OP)
Hi,
Is it possible to convert from picoAmps to Hertz? If not, what is the relationship?
Thanks,
Glenn
Is it possible to convert from picoAmps to Hertz? If not, what is the relationship?
Thanks,
Glenn





RE: conversion question
RE: conversion question
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If we learn from our mistakes,
I'm getting a great education!
RE: conversion question
Are you just trying to measure picoAmp currents?
Depending on measurement period allowable, the following approach may be of interest. At a company I worked for some years ago we needed to measure this sort of current very accurately. We used the technique of passing the current into a precision air-spaced dielectric capacitor for a known time (30-40 seconds), then measured the voltage with a very high input impedance (electrometer input)DVM.
The simple calculation I = C.dv/dt gives the current.
RE: conversion question
There are many articles about voltage to frequency converters and there are IC's just for this purpose.
Yes there are other manufactures of operational amplifiers and resistors that will work. Also there are other circuits that will work.
Good Luck
RE: conversion question
RE: conversion question
RE: conversion question
I am curious as to what you were actually trying to do or think about. Where was the current coming from and what was the reason for wanting to scale this to frequency?
RE: conversion question
RE: conversion question
Hertz = cycles/sec
therefor the convertion is (1)pA= (1)Hz* (1)picocoulomb/cycle
or (1)pA=(1)Hz*(1)coulomb/(1)Gigacycle.
Obvious I thought.
RE: conversion question
RE: conversion question
I'm not actually attempting to build or design anything. I was looking at two graphs. One had a y-axis in pA and another had a y-axis in Hz. I was attempting to compare the two on level ground.
RE: conversion question
Unless the two are related by some other factor - capacitive leakage current increasing with frequency springing to mind as one example - there is no implicit relationship between the two.
davidbeach - you were right all along!
GOTWW - you have me confused, or you are confused. I am not sure which!
----------------------------------
If we learn from our mistakes,
I'm getting a great education!
RE: conversion question
Im sure that the conversion could be done. Think about this:
if they can use voltages to convert to frequencies (Voltage controlled oscillators), then it makes sense that you can do the same with current.
its been a long time that i've dealt with op-amps, but I think that there might be a configuration out there that takes a current input and gives an amplified voltage output.
(Current to voltage amplifier). But, theres a problem with such a small current signal--noise. You must clean up any noise. If this could be done, then use the current to voltage amplifier, then use the voltage output to drive a VCO. The output of the VCO is a sinusoid (Sine wave), whose frequency changes according to the input voltage.
Good Luck.
RE: conversion question
RE: conversion question
"if they can use voltages to convert to frequencies (Voltage controlled oscillators), then it makes sense that you can do the same with current."
That does not mean there is any inherent relationship between the units being discussed. If you use a circuit to convert from current to frequency, the conversion factors are dtermined by the circuit and the values of the components. If you change the value of a particular capacitor, for instance, you change the conversion factor.
RE: conversion question
This thread left reality almost from the beginning. You brought it back to terra firma. I certainly hope that this ends it.
RE: conversion question
When using SI base units one should be careful since, for example, in radioactivity the Bq = 1 decay/s, is expressed as s-1, the same as for frequency.
RE: conversion question
I guess it is back to the old issue of making sure that you don't confuse the map with the terrain.
Bung
Life is non-linear...