The value for Rmemb is correct, when a test pulse is running. Why then does the Rmemb value appear to be meaningless, when I turn the test pulse off or switch to the oscilloscope window?
The Rmemb value is computed in two ways: When a test pulse is running, Rmemb is computed as: Rmemb = dU / d I = Test Pulse Amplitude / ( CurrentTestPulseSegment 1 – CurrentTestPulseSegment 2) When no test pulse is running, Rmemb is computed as: Rmemb = Vmemb / Ipip = Measured Steady StateVoltage / Measured Steady State Pipette Current The first formula estimates Rmemb by the relative current change evoked by the voltage jump in the test pulse. This kind of Rmemb estimation is insensitive against leak currents, a possible reversal potential, and uncompensated amplifier offsets. Also, the applied test pulse amplitude as well as the evoked current can be measured with good precision. The second formula has some major shortcomings. It is sensitive to leak currents, a possible reversal potential, and uncompensated amplifier offsets. Also, precision artifacts can occur, especially when holding the cell at zero holding potential or when the measured current is very small. In most situations i
