Hi all,
We are trying to perform some 4-probe measurements using the SMU4141 and would like to understand some limitations we have noticed. When the lead resistance is low, measurements are correct, but they start deviating when the lead resistance becomes large compared to the DUT resistance.
For instance, if we connect a 25kohm resistor between HIs and LOs and 1kohm resistors between HIs - HI and LOs - LO, then the measurement is correct. However, if we would use 25kohm resistors also between HIs-HI and LOs-LO, then the measurement would be wrong, even if we set the SMU to local sense. What would be the actual limit for the lead resistances?
We have read that there is a maximum voltage drop of 1V that the SMU can apply across the higher current output leads. However, that would not explain the deviation we measure since we see it even applying small voltages at the SMU channel output.
Also, we read in the forum that there is an internal pull resistor from each sense lead to the respective HI/LO pin. This might explain the limitation; if this is the case, what is the actual value of these pull resistors? Also we noticed that even if the sense terminals are open, the two terminal measurement is correct, is that also explained by the internal pull resistors?
Thanks in advance for your answer,
Juan
