A measurement indicator on the driller´s console on the derrick floor showing hook load and weight-on-bit. It contains two needles, one gives the weight hanging from the hook and the other gives the difference between the drill string off bottom and on bottom, i.e. the weight on the bit.
The weight indicator can be a) attached to the travelling block to directly measure the hook load, b) attached to the dead line and use a bend in the line to measure tension on the line, or c) a pressure transformer and indicating gauge connected with hydraulic hose.