How do you test wire connectors?

Question

Assume you start with a 12 inch piece of 16guage stranded automotive wire for each connector test.

You then check continuity and resistance for the wire.

Then you cut the 12 inch piece of wire in half and try reconnecting one end of each wire with following methods.

1) Soldered ends together

2) male/female spade connector

3) ring terminal bolt ring terminal

4) twisted ends together w/ twist cap

Then you check continuity and resistance for each different type of connector.

How can you tell if you have connected the two wires properly? i.e. soldered correctly, or crimped the spade connectors snug enough, or twisted the ends properly or tight enough?

How do you do this with a multimeter?

Answer 1

set your multimeter to the ohms position. If you have good continuity the meter should almost zero, if there is a bad connection the meter will read infinite.

Answer 2

It sounds as though you're trying to measure the difference between the various types of connections.  Is that right?

One difficulty is that multimeters, unless they're laboratory-grade, aren't very accurate at measuring very low resistance values. I don't think you'll get any meaningful results doing continuity and resistance measurements.

An accurate way to determine the resistance in a connection is to measure the voltage drop across the connection.  To do this, you'll have to connect a power supply and a resistive load in series with the connection.  You'll also need an ammeter so you can tell how much current is flowing through the circuit.  Set your multimeter for volts, and place one probe on each side of the connection.  The voltage reading represents the amount of voltage lost through the junction.   With the voltage and current measurements, you can use Ohm's Law to calculate the resistance in the connection.

However, if you find a resistance, there's no easy way to tell whether it's due to an error in making the connection, or an inherent loss in the type of connection itself.  Probably the only way is to repeat the test several times for each connector type, discarding any results that are significantly different from the average.  

Given that all of these connection types are used very commonly in car or home wiring, I don't think you'll find much of a significant difference in each of them in terms of resistance.  There are other factors that make each of them a good or bad choice in various wiring situations.