measure, scales, weigh
銓 centers on the act of measuring weight or value: using scales to weigh something, or figuratively assessing and judging.
銓 combines 金 (metal) with 全, which likely contributes the sound and the idea of completeness or wholeness, suggesting a metal weighing instrument that gives a full measure.
Metal 金 on the left and 全 (whole, complete) on the right: picture a metal scale that gives a complete, accurate weight.
For セン, imagine a metal scale sending a signal when the weight is perfect: send -> セン, and the scale measures exactly.