Determining elecrtic power (Praxis)

As declared in the previous chapter we need to determine the unknown voltage and current on the different supply points. Let´s head to the unproblematic voltage-measuring. For this purpose we just take a multimeter from Temna which delivers for one decimal exactly the same results as our calibrated reference measurement equipment. We measured voltages directly at the contacts of the PCI-Express-Slot respectively the contacts of the 6-pin and 8-pin-connector.


In case of current we used the way of contact free measuring with a current clamp - once again from Temna. In this way measuring the current flow through the 6-pin and 8-pin-connectors was not a problem at all, but determining current flow from the PCI-express-slot wasn´t that easy and we had to solder cables at the according pins to measure the current. Voltage drop generated by the inserted cables is in a negligible range, as we confirmed by measurement of overall system-power before and after modification.


The Temna-device is a True-RMS-clamp-meter. This is necessary because the graphics card isn´t purely ohmic but a reactance with transients. This current clamp was calibrated using a Fluke 9100 Universal Calibration System (Standard calibration like described in DIN EN ISO 9000 / 9001 referring to DIN EN ISO/ IEC 17025 (ISO Guide 25). Measuring Tolerance: up to 30A: +-0,08% +2mA, up to 105A: +-0,08% +11mA.