The requirements for cylinder pressure measurement for mechanical load, imep, and cycle analysis are developed. Methods for determining errors in transducers are presented, and the results are shown. The tests include passage error, hysteresis, nonlinearity, mounting strains, thermal strain, and twist in the crankshaft. Theories are developed to predict errors due to time or phase delay, passage, and thermal strain. The theory of the balanced pressure indicator is developed and the minimum delay and pressure error are calculated. Read-out systems are evaluated. Areas needing improvement are pointed out and specifications for the ideal pressure transducer are presented.