The NIST 30 MHz Linear Measurement System

An automated linear measurement system (LMS) has been developed to determine the nonlinearity of a tuned 30 MHz power detector over a 6.021 dB range. This detector uses a single thermistor bead design with thermal isolation to obtain nearly linear tracking over a 4:1 change in input power. The nonlinear correction for this change, determined by the LMS, is on the order of 1.00030 (+130 μB) for the detector presently in use. Initial experiments indicate an expanded uncertainty of ±0.138% (±598 μB), which is based upon Type A and Type B components.