A method and a current sensor for measuring a current in a conductor. The sensor comprises a non-magnetic, flexible core member having a first end and a second end. A locking head having a channel therethrough is coupled to the first end of the core member. A first sensor conductor winding layer is mounted on the core member. Wherein the second end releasably engages the locking thread in the channel and adjustably configures the core member to surround the conductor as the second end is moved through the channel. In another embodiment the current sensor includes a locking tang within the channel and a plurality of sought tooth members on a portion of the core member and configured to selectively engage the locking tang as the second end of the core member is moved through the channel.