Measurer (5)
(Other definitions for ruler that I've seen before include "It helps to draw straight lines" , "Sovereign - support for a firm line!" , "Monarch - straightedge" , "king perhaps" , "Measuring strip" .)
(Other definitions for meter that I've seen before include "Measuring device as for electricity consumption" , "Apparatus for measuring" , "Instrument for measuring quantity" , "Device to measure quantity used of fluid, electricity etc" , "Measuring device as for electricity usage (5)" .)