In terms of the operating time, yes it looks quite broad once you are the 'not really instant' part of the curve, assuming the curves you have posted are for the right breaker and setting case, then I agree with your conclusion..


However, before panicking, and if you are seeing a lot of marginal fails like this on test,  and yet really there are no volt drop issues or visual signs of things cooking it is worth pointing out that an MFT, depending on the model, may or may not be accurate to tens of milliohms, even when meeting the maker's factory test spec with brand new clean and nulled leads and nice bolted joints (not scratchy probes on slightly tarnished screw heads). That back page of the meter  handbook about accuracy and tolerances  is the first thing to check, and/ or the length and cable type.



(For example This dataasheet from Megger  suggests an accuracy on lop tests of  5% of reading +/- 5 counts in the least significant digit.

So if the reading on the display was 0.080  then the real value to generate that could lie  anywhere between 0.071 to 0.089   (5% is 4 in the last place plus another 5 counts),

OK, but worse, while on a less sensitive setting , if the reading on the display was on a range such that it was showing 0.08 ohms, then that reading could be generated by a true value of anything from 0.03 to 0.13.  Neither would be  considered convincing.  Of course by you add a set of leads that have spent more than  a week in the toolbox and busbars that are no longer golden and bright, the uncertainty rises, usually on the upside.  Your meter may be better, but check.)

In terms of the operating time, yes it looks quite broad once you are the 'not really instant' part of the curve, assuming the curves you have posted are for the right breaker and setting case, then I agree with your conclusion..


However, before panicking, and if you are seeing a lot of marginal fails like this on test,  and yet really there are no volt drop issues or visual signs of things cooking it is worth pointing out that an MFT, depending on the model, may or may not be accurate to tens of milliohms, even when meeting the maker's factory test spec with brand new clean and nulled leads and nice bolted joints (not scratchy probes on slightly tarnished screw heads). That back page of the meter  handbook about accuracy and tolerances  is the first thing to check, and/ or the length and cable type.



(For example This dataasheet from Megger  suggests an accuracy on lop tests of  5% of reading +/- 5 counts in the least significant digit.

So if the reading on the display was 0.080  then the real value to generate that could lie  anywhere between 0.071 to 0.089   (5% is 4 in the last place plus another 5 counts),

OK, but worse, while on a less sensitive setting , if the reading on the display was on a range such that it was showing 0.08 ohms, then that reading could be generated by a true value of anything from 0.03 to 0.13.  Neither would be  considered convincing.  Of course by you add a set of leads that have spent more than  a week in the toolbox and busbars that are no longer golden and bright, the uncertainty rises, usually on the upside.  Your meter may be better, but check.)