Elaborate explanation on weighing and resistance measurement of the coils for the stator alternator. Closes #8

5.Let's-build/Alternator/Alternator-Stator.md

@@ -26,7 +26,13 @@ Once you have set up your Coil Winder, start making the first coil. Our coils ha
 
 ## 3. Weigh and measure the resistance of every single coil
 
-All coils must be similar in order to have a constant load. To achieve this, use a scale to compare the weight of the coils and measure the resistance with a multimeter.
+All coils must be similar in order to have a constant load. To achieve this:
+
+1. Use a scale and measure the weight of the coils. They weight should be consistent within around +/- 5%.  If it is to heavy it either indicates a counting error or it is wound very loosly.
+
+2. Measure the resistance of each coil with a multimeter set on resistance measurement. More accurate resistance results are obtained by using a DC power supply and run a defined current of e.g. 5 A through the coil while measuring the voltage drop with a multimeter set on voltage measurement on both ends of the coil. You can then calculate the resistance of each coil by R = U/I. 
+
+If one coil differs a lot from the others in weight or resistance it´s better to reject this coil and either straighten the wire of this coil or use new wire to wind a new one.
 
 ## 4. Draw a template