Timeline for Avoid cross talk between recording electrodes
Current License: CC BY-SA 4.0
9 events
| when toggle format | what | by | license | comment | |
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| Apr 18 at 21:52 | comment | added | Fabio Barone | Excellent news. If you have high-impedance volt meters to measure the electrode voltages independently, then it would be interesting to plot the reported difference voltage WE_out (& RE_out) vs the common-mode voltage at the INA121 inputs (the average of the two voltages at WE_1 & WE_2). Ideally, if WE_1 & WE_2 are connected together, & connected to a node with an adjustable voltage (lets call this voltage Vcm), then WE_out should remain at 0mV while Vcm remains within the common-mode range of the INA121 (which is stated on the datasheet). | |
| Apr 18 at 13:49 | comment | added | Potatoconomy | Thanks Fabio for your input. I removed the resistors connecting the non-inverting inputs to AGND and simply connected AGND with a physical electrode (I did forget the R2 10k resistor but that can be done later). Doing this immediately allowed me to read values that mostly agreed with other high impedance voltmeters from the electrodes. I say mostly agreed, because depending on the electrode type used for this connection, a different DC bias (on the scale of 0.5-1 mV) was introduced in the amplifier/ADC read out. | |
| Apr 18 at 13:49 | vote | accept | Potatoconomy | ||
| Apr 14 at 9:30 | comment | added | Fabio Barone | Excellent, looking forward to seeing your results. Note that the value of R2 is rather arbitrary here; it can probably be reduced to zero, however, leaving it as 10k may be useful as a means of measuring the current flowing into the conducting fluid from the ground connection. | |
| Apr 13 at 12:44 | comment | added | Potatoconomy | Thanks Fabio, I will try this next week and report back here what happens. | |
| Apr 13 at 2:10 | comment | added | Fabio Barone | The app note associated with the INA121 may be quite relevant. SBOA503, Importance of Input Bias Current Return Paths in Instrumentation Amplifier Applications | |
| Apr 13 at 2:05 | history | edited | Fabio Barone | CC BY-SA 4.0 |
Added note about INA121 having 36V supply rail.
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| Apr 13 at 1:55 | history | edited | Fabio Barone | CC BY-SA 4.0 |
added 165 characters in body
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| Apr 13 at 1:46 | history | answered | Fabio Barone | CC BY-SA 4.0 |