In an effort to evaluate simple and accurate display for my various Power projects a little while back including my analogue DC load , I found and bought some panel meters from aliexpress here
http://www.aliexpress.com/item/Blue-R...
on initial examination hey seemed to have issues when used for all but the basic systems but......

on receint examination I discovered that they use a seperate differential input ADC chip to read the current that has markings "CA2P" and had shorted the negative input to the 0V rail of the power / Voltage sense input with a zero ohm value resistor negating its differential ability and in the processess limiting its flexability.

I will show you here how to Hack it back to a differential input and how I integrated it into a DC Load

Now these displays have a whole new lease on life...