New Calibration test
This time all meters are hooked up to a single ATX power supply:
MeterVoltage
Fluke 7712.49
Tektronix 50212.49
Cen-Tech P9867412.55
Tenma 72-402512.48
Cen-Tech 9202012.46
Cen-Tech P3349912.51
Viz WD75012.58
Average is 12.51 V
Standard Deviation is 39.1 mV
Ugh. Standard Deviation got worse.