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### Measurement of electronic distances.

Posted: **Fri May 03, 2013 11:16 am**

by **gary**

Apologies in advance for another obtuse question.

I enjoyed working through the electronic analysis tutorial at

http://www.neuron.yale.edu/neuron/stati ... zclass.htm using the NEURON GUI. Returning to my Python code, I am attempting to perform a similar analysis however I cannot see an obvious way to return the value of `attenuation' or `log(attenuation)'. Looking at

http://www.neuron.yale.edu/neuron/stati ... html#ratio , the impedance class' function `ratio' is the closest thing I can find. Or is the attenuation measurement not available for the programmer?

### Re: Measurement of electronic distances.

Posted: **Fri May 03, 2013 11:25 am**

by **ted**

The voltage transfer ratio is

voltage downstream / voltage upstream

and is always <= 1.

Voltage attenuation is simply 1 / voltage transfer ratio, so that a bigger number means more attenuation (makes sense, right?).

### Re: Measurement of electronic distances.

Posted: **Fri May 03, 2013 11:48 am**

by **gary**

Thanks for an incredibly swift answer!

ted wrote:(makes sense, right?)

I *think* so. You can score my responses to your reply as to whether or not I really do understand!

ted wrote:The voltage transfer ratio is voltage downstream / voltage upstream and is always <= 1.

If this refers to Impedance.ratio(x) - I interpret this as downstream voltage recorded at the CAS at location x divided by the size of the upstream voltage source located according to Impedance.loc() after calculation with Impedance.compute(freq, flag). Since voltages can't `grow', this means its value must be <=1.

ted wrote:Voltage attenuation is simply 1 / voltage transfer ratio, so that a bigger number means more attenuation (makes sense, right?).

Or: log_e(Attenuation) = -log_e(Ratio) = my measurement of electronic distance in units of nepers?

### Re: Measurement of electronic distances.

Posted: **Fri May 03, 2013 4:13 pm**

by **ted**

In discussing the potential at two points, it is convenient to use "upstream" to refer to the point that is closer to the signal source, and "downstream" for the point that is farther away.

gary wrote:log_e(Attenuation) = -log_e(Ratio) = my measurement of electronic distance in units of nepers?

A native of the realm of neuroscience would not even know such a term existed. You betray your infiltration from some other province of geekdom.