An analog instrumentation for estimating dimensions of chaotic dynamical systems has been developed. The technique employs time series of the Poincare´ points successively displayed on the screen of an oscilloscope. It provides a rapid way to estimate the pointwise dimension from a single variable directly in an experiment. The instrumentation is easy to build and is convenient to employ. We have tested it by applying to periodic and quasiperiodic oscillators, and have verified by means of the fractal two‐dimensional Poincare´ map, simulated from the Duffing–Holmes differential equation. The measured values well agree with the computer calculated ones.