Weighing would only be slightly better than a simple parity check (a one-bit hash). It misses common errors like transposing two adjacent characters. However,

Weighing would only be slightly better than a simple parity check (a one-bit hash). It misses common errors like transposing two adjacent characters. However, you can get any number of additional bits by suspending the punch card from various locations along its perimeter, and measuring the angle at which it hangs.