rtorsvik

Hello! I am developing a board for the AD3, and I want to utilize its positive and negative power supply to provide +5V and -5V for an op-amp. This works mostly fine, but in some cases, my board loses power, and I suspect it is due to the AD3 limiting its output. Is there some way I can adjust the power limit using the SDK, just as I can adjust the power limit with the WaveForms application? This is how I activate the power supplies today. def activate_supply(self, master_state=1, positive_state=1, negative_state=1, positive_voltage=5, negative_voltage=-5): """ turn the power supplies on/off parameters: - device data - master switch - True = on, False = off - positive supply switch - True = on, False = off - negative supply switch - True = on, False = off - positive supply voltage in Volts - negative supply voltage in Volts """ log("Activating power supplies...", "info") # set positive voltage positive_voltage = max(0, min(5, positive_voltage)) dwf.FDwfAnalogIOChannelNodeSet(self.device, ctypes.c_int(0), ctypes.c_int(1), ctypes.c_double(positive_voltage)) # set negative voltage negative_voltage = max(-5, min(0, negative_voltage)) dwf.FDwfAnalogIOChannelNodeSet(self.device, ctypes.c_int(1), ctypes.c_int(1), ctypes.c_double(negative_voltage)) # enable/disable the positive supply dwf.FDwfAnalogIOChannelNodeSet(self.device, ctypes.c_int(0), ctypes.c_int(0), ctypes.c_int(positive_state)) # enable the negative supply dwf.FDwfAnalogIOChannelNodeSet(self.device, ctypes.c_int(1), ctypes.c_int(0), ctypes.c_int(negative_state)) # start/stop the supplies - master switch dwf.FDwfAnalogIOEnableSet(self.device, ctypes.c_int(master_state))

Hi @attila, thank you so much for your feedback. Based on your answer I have done some more research and now I have some follow-up questions. I added some buffer stage opamps with high input impedance such that I should not have to take voltage drop over the 1M internal pulldown resistors into account. Also, this should limit the current through the pick-up electrodes in the middle. Now, all the current going through the current carrying should go to GND and I should be able to calculate impedance Z as Z(ω) = ΔV(ω) / I(ω), where ΔV(ω) is the Fourier transform of ΔV(t), the voltage drop over the membrane, and I(ω) is the Fourier transform of I(t) So the questions regarding this solution: If you set the WaveForms impedance tool mode to "Constant Current" and a current to for instance 1mÃ, this will give me a sinusoidal excitation where the peak or RMS currents are 1 mA? ( i.e. W1 = 1mA*sin(ωt) ) Are you able to get/read the internal data from the wave generator so that I can actually process the data? (using the script tool maybe)

Hello! I am looking into making a 4 wire setup for impedance measurement over a membrane as shown below (left). I was thinking I could use the BNC adapter and connect wavegen 1 and channels 1 and 2 as follows (right) and then use the WaveForms Impedance Analysis tool to do the measurements. However, after some experiments with the software, it seems that WaveForms bases its impedance calculations on what reference resistors you chose, which I don't have in my setup. Is there any way to get around this? The four-electrode system is interesting because the measuring electrodes ch1+ and ch2+ do not carry any current as they are separated from the electrodes applying a voltage to the electrolyte solution. Hence there should be no buildup of material, electrolysis, or electrode polarization impedance at the measuring electrodes. Some similar topics were touched upon in this thread https://forum.digilent.com/topic/16915-ad2-as-a-electrochemical-impedance-meter-is-possible/ Best regards rtorsvik