
2022-05-11.

In response to our own sadness of having not taken the EIS further down the frequency range (and the reviewer's comment on the same issue) we went further. 

To save time, it was done by using the IDAX directly, with a big capacitor (66 uF) just to block the battery from driving DC. 
This was not as good as the plan of using a real HV source and smaller capacitor so as to make close to a constant current source.  

The file controlling the IDAX ('icf') had lines inserted to make single-point measurements at a list of voltage&frequency combinations, with voltage*frequency product constant where possible within the range of source voltage (max 200V, reasonable min several mV or preferably more, given that it's 32bit +-10V and thus ~0.3 mV quantization). 

The range was 460---0.01 Hz.  

The results actually overlapped surprisingly well with most of the ones from the earlier EIS measurements that used an oscilloscope and signal generator and covered 10Hz--30kHz.  Those ones were poor on the lower end, with weak signal, so 400 Hz was used as the joining point for plotting the two sets together. 

Note that the batteries used on the two occasions were different ones, though from the same batches.  That was because the original ones had been used for short-circuit tests, so it was wondered if they might be somewhat changed.  That the curves anyway fitted so well is pleasing for the generality of results. 

The alkaline battery's loss was the main detail that showed a marked difference between the two measurement sets.  Possible explanations are different current (the alkaline battery was seen to show nonlinearity in these IDAX tests; the first batch of tests used tens of mA most of the way, whereas this second batch by IDAX aimed for 1 mA and were generally below that, particularly with the alkaline at low frequency), or the different batteries. 





