Anonymous
Anonymous asked in Science & MathematicsBiology · 2 months ago

# Why is 100 mV the best range to be selected on an electrometer?

I am running a test using an Ussing chamber to determine membrane potentials.

I have been asked why 100 mV us a good range to use?

BSc Biology

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• Zirp
Lv 7
1 month ago

Well, that depends on what you use it for.

For the electricity that runs your household-appliances such a range would be useless

• 2 months ago

Typical membrane potentials are between -40mV and -80mV.  The 100mV range maximises the display precision for these values.

If that’s not clear, here’s a more detailed explanation.

Consider a 4 digit display.  Ranges usually change in factors of 10. Suppose the potential is 51.23mV.

The 10mV range is too small.  The display can only show values from 0 to +9.999mV or 0 to -9.999mV An ‘over-range’ symbol will be displayed is -51.23 is outside the possible range.

A range of 1000mV (=1V) will work but you lose 1 digit precision.  The display will show -051.2 so you only get 1 decimal place. (The leading may be shown as a blank.)

But using the 100mV range the display is -51.23 which gives 2 decimal places.

• 2 months ago

Probably because some grad student or undergrad spent a summer figuring out what worked best.  Check the literature for the paper(s) that were written by that "team."