Originally Posted by DaveInDenver
Problem is a handheld DMM is not accurate enough to really measure
I have yet to encounter a modern DMM that isn't accurate enough for general automotive applications. Even the little $4 jobs that HFT sells. They work just fine for our automotive applications. We're not measuring cold fusion here.
I spent several decades in metrology, and spent quite a bit of time up at NIST in Boulder and the Danish Institute for Fundamental Metrology in Copenhagen. I certainly know uncertainties and sources of error. The latter will get the uninitiated, but not modern DMMs' accuracy.
FWIW, "Accuracy" is a combination of precision (repeatability), and calibration to some accepted standard, such as NIST, and of course resolution. You can have resolution to however many digits past the decimal place but still have poor precision or be uncalibrated. You can have great precision and calibration but insufficient resolution. When you have all three, you are generally good, but still need to know how to apply your instruments to achieve their potential.
For milliohm measurements we always use a Kelvin connection for our milliohmmeter. Using a milliohmmeter, you can use a regular DMM in parallel and discover techniques that allow a regular handheld DMM to give you really accurate measurements, so that when you learn the techniques you no longer need the fancy milliohmmeter and kelvin connections for your automotive troubleshooting and diagnostics.