Abstract: A method and apparatus for measuring node voltage on an integrated circuit is diclosed herein. A sensing needle 10, which is connected to supply voltage 20, is positioned directly above node 12 on integrated circuit 14. Tunneling or field emission current 30 is produced in sensing needle 10 due to the difference in potential between sensing needle 10 and node 12. Supply voltage 20 is adjusted to set current 30 to an initial value. When the voltage on node 12 changes, the current 30 will also try to change. When a change in current 30 is detected, a signal 28 is generated to adjust supply voltage 20 such that current 30 returns to its initial value. Consequently, the change in supply voltage 20 mirrors the change in voltage on node 12.