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THD and Audio Analysis Multimeter

Our audio analyzing multimeters combine audio band quality measurements and analysis with a broad purpose 6½-digit DMM—all in one half-rack instrument. They can measure total harmonic distortion (THD) over the complete 20Hz to 20kHz audio band and can compute THD+Noise and signal-to-noise plus distortion (SINAD). The 2015‑P and 2016-P directly identify peak values of the frequency spectrum. The 2016 and 2016-P have twice the sine wave generator output of the 2015 for applications that require test signals greater than 8Vrms.


  • THD, THD+Noise, and SINAD measurements
  • 20 Hz–20 kHz sine wave generator
  • Fast frequency sweeps
  • 2015-P identifies peak spectra components
  • Sine wave generator maximum ampitude: 4 Vrms single-ended or 8 Vrms differential output
  • Individua harmonic magnitude measurements
  • 5 standard audio shaping fiters
  • 13 DMM functions (6. digits)
  • GPIB and RS-232 interfaces

Frequency Domain Distortion Analysis

For applications such as assessing non-linear distortion in components, devices, and systems, DSP-based processing allows the 2015 and 2015-P to provide frequency domain analysis in conventional time domain instruments. They can measure Total Harmonic Distortion (THD) over the complete 20 Hz to 20 kHz audio band. They also measure over a wide input range (up to 750 Vrms) and have low residual distortion (–87 dB). The THD reading can be expressed either in decibels or as a percentage.

In addition to THD, the 2015 and 2015-P can compute THD+Noise and Signal-to-Noise plus Distortion (SINAD). For analyses in which the individual harmonics are the criteria of greatest interest, the instruments can report any of the (up to 64) harmonic magnitudes that can be included in the distortion measurements. The user can program the actual number of harmonics to be included in a computation, so accuracy, speed, and complexity can be optimized for a specific application.

Dual Output Source

The 2015 and 2015-P include an internal audio band sinewave source for generating stimulus signals. A secondoutput, the inverse of the first output, is also available,simplifying the testing of differential input circuits forcommon mode or noise cancellation performance. The2015 and 2015-P have a 4 Vrms single-ended output and8 Vrms differential source output.

Wide Selection of Audio Filters

Five industry-standard bandpass filters are provided for shaping the input signal for audio and telecommunication applications. Available filters include the CCITT weighting filter, CCIR filter, C-message filter, CCIR/ARM filter, and “A” weighting filter (see Figures 5a–5e). The 2015 and 2015-P provide programmable, high cutoff (low pass) and low cutoff (high pass) filters. Furthermore, the two filters can be implemented together to form a bandpass filter. The programmable filters can be used to filter out noise generated by electromechanical machinery on the production floor or to simulate other types of system transmission characteristics.

Broad Measurement Flexibility

In addition to their THD, THD+Noise, SINAD, and individual harmonic measurement capabilities, the instruments provide a comprehensive set of DMM functions, including DCV, ACV, DCI, ACI, 2WΩ, 4WΩ, temperature, frequency, period, dB, dBm, and continuity measurements, as well as diode testing. This multifunctional design minimizes added equipment costs when configuring test setups.

Wide Band or Narrow BandNoise Measurements

The 2015 and 2015-P are capable of measuring both wide band noise and narrow band noise. Alternatively, these instruments’ DSP (digital signal processing) capabilities allow users to make frequency domain measurements of RMS voltage noise over the 20 Hz–20 kHz frequency audio band or a narrow portion of the band. Furthermore, noise measurements can be extracted in the presence of a stimulus signal for fast signal-to-noise computations.

Spectrum Analysis

The 2015-P has internal computational capabilities that allow it to characterize an acquired signal spectrum. This instrument can identify and report the frequency and amplitude of the highest value in a complete spectrum or within a specified frequency band. It can also identify additional peaks in descending order of magnitude. The 2015-P’s onboard capabilities make it simple to obtain a thorough analysis of a frequency spectrum more quickly and with little or no need for external analysis software.


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