First off, I know these are called "barrel connectors" but also go under other names. So, I am referring to these:
Great, I suppose I could use a micrometer to measure the outside of the connector, but what about the thickness of the center terminal that goes in the hole on the connector. How do you measure them? Worse yet, how do you measure the inside of the hole on the rear of a device that needs one of these connectors? (such as on the rear of a radio that needs a wall wart)?
Over the years, I have used the trial and error method. Take the device to the store and begin plugging them in until one of them fits. But these days, if I go to Radio Shack for example, they are all packaged in sealed plastic and the store manager wont just let me open all the packages. Worse yet, trying to order them online....
Is there any system or method to this madness of sizes? I was told that they are sized according to voltage of the wart on the other end of the cord. It does appear that the higher voltages have thicker and larger connectors, but I have seen variances in the sizes for the same voltage, such as 6 volt ones that may be 5.5mm or 8mm, or ????? Sometimes the outer part will fit, but not the pin in the center. More than once I have drilled out the center holes to make them fit.
This all seems like a jungle of chaos. Is there any way to easily measure and determine what is needed (for both the male and the female parts).
Thanks