The AA501 Distortion Analyzer provides measurement of level, total harmonic distortion plus noise (THD+N). Operation is made simple, select the mode and the rest is automatic! The fundamental frequency range is 10Hz to 100kHz, with harmonics measured out to 300kHz. The distortion ranges are auto (100%), 20%, 2%, 0.2%, and dB (autoranging). The unit allows readings to be expressed in true rms or average response and rms calibrated. Any one of four built-in frequency-weighting filters may be switched into the signal paths for preconditioning of the signal to be measured. Provision is also made to permit the use of a user-selected filter as well. The digital voltmeter has input range of 200 ?V to 200 V (10 steps) plus auto range and will display signal level in volts, dBm, or dB ratio. Other features include input monitor, function output, and auxiliary input connectors. It utilizes 2 slots in a Tek TM-Series Power Module (sold separately).