| | Calculating Electrode Impedance Using a Table
| Vm | Ze | | (mV) | (kW) | | 50 | 1000 | | 52 | 923 | | 54 | 852 | | 56 | 786 | | 58 | 724 | | 60 | 667 | | 62 | 613 | | 64 | 563 | | 66 | 515 | | 68 | 471 | | 70 | 429 | | 72 | 389 | | 74 | 351 | | 76 | 316 | | 78 | 282 | | 80 | 250 | | 82 | 220 | | 84 | 190 | | 86 | 163 | | 88 | 136 | | 90 | 111 | | 92 | 87 | | 94 | 64 | | 96 | 42 |
| | In our lab, we use this table (left) to compute electrode impedance (Ze) from a measured voltage (Vm). The table applies to measurements made using the circuit in Metal Microelectrodes for Recording in Behaving Animals and these parameters: |
| Source voltage: V0 = 100 mV pk-pk, sinusoid (100 Hz)
| Oscilloscope internal impedance: Rm = 1 megohm
| | You may wish to adapt this technique for your particular situation. To do this, create a spreadsheet using an equation to compute impedance from your setup-specific parameters. One possible variation from our setup would use a digital voltmeter instead of an oscilloscope. This substitution would most likely require you to change Rm from 1 megohm to 10 megohms as most digital voltmeters have 10 megohms internal impedance. If you decide to use a digital voltmeter, make sure you are measuring "AC volts". |
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Web Content from: Schoenbaum, G. Olfactory Learning and the Neurophysiological Study of Rat Prefrontal Function. In: CRC Series: Methods and Frontiers in Neuroscience. Edited by S.A. Simon and M.A.L. Nicolelis, CRC Press, NY, 2000.
This web page coauthored by Kevin B. Austin, PhD., Eclectic Engineering Studio, www.EclecticStudio.com 
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