A Simple Test for Phase Characteristics of Chart Recorders

A method for quantifying the relative phase shift characteristics of chart recorders is presented. A test signal of the form (cos wot + A cos 3wot) is used, which when normalized for unequal responses at the two frequencies, provides an independent quantitative measure of relative phase shift which can be detennined from examination of the output record. Ihe ease of implementation and interpretation suggests the potential application of this test as both a compliance and quality assurance technique for evaluating the performance of medical chart recording systems.