The Quad Current Meter is a tool for matching servos on giant scale aircraft flight surfaces.   Any of us who have set up a GS plane know what a pain it can be to set up servos.  

Listening for servo buzzing, using a volt meter to measure each servo, feeling linkages for binding.  The most used method by far is the use of a Digital Volt Meter set and configured to measure amperage.   Jumping from servo to servo and then back again as you make smaller and smaller adjustments.  

Enter the QCM.   With a single unit you can now plug in all 2, 3, or even 4 servos and measure their individual current on the same screen.    

Picture 3 - is a picture of QCM screen shots of a "4 servo group" of servos being manipulated with a QCM connected.