Audio analyzing and total harmonic distortion DMMs
DIGITAL MULTIMETERS & SYSTEMS
www.keithley.com
1.888.KEITHLEY (U.S. only)
A GREATER MEASURE OF CONFIDENCE
2015, 2015-P,
2016, 2016-P
61⁄2-Digit THDMultimeters
61⁄2-Digit Audio Analyzing Multimeters
The Models 2015-P and 2016-P Audio Analyzing
Digital Multimeters and the Models 2015 and 2016
Total Harmonic Distortion Multimeters combine
audio band quality measurements and analysis with
a full-function 6
1
⁄2-digit DMM. Test engineers can
make a broad range of voltage, resistance, current,
frequency, and distortion measurements, all with
the same compact, half-rack measurement instrument. The Model 2016 and 2016-P have twice the
sine wave generator output of the Model 2015 for
applications that require test signals greater than
8Vrms. The Model 2015-P and 2016-P offer additional processing capacity for frequency spectrum
analysis.
Frequency Domain Distortion Analysis
For applications such as assessing non-linear distortion in components, devices, and systems, DSPbased processing allows the Models 2015-P, 2015,
2016, and 2016-P to provide frequency domain
analysis in conventional time domain instruments.
They can measure Total Harmonic Distortion (THD) over the complete 20Hz to 20kHz audio band.
They also measure over a wide input range (up to 750Vrms) and have low residual distortion
(–87dB). The THD reading can be expressed either in decibels or as a percentage.
In addition to THD, the Models 2015, 2015-P, 2016, and 2016-P can compute THD+Noise and Signalto-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. (See Figure 1.)
APPLICATIONS
• Wireless communication device
audio quality testing
• Component linearity testing
• Lighting and ballast THD limit
conformance testing
• Telephone and automotive
speaker testing
• THD, THD+Noise, and SINAD
measurements
• 20Hz–20kHz sine wave
generator
• Fast frequency sweeps
• 2015-P, 2016-P: Identifies peak
spectral components
• 2015, 2015-P: 4Vrms single-
ended or 8Vrms differential
output
• 2016, 2016-P: 9.5Vrms single-
ended or 19Vrms differential
output
• Individual harmonic magnitude
measurements
• 5 standard audio shaping filters
• 13 DMM functions (6
1
⁄2 digits)
Figure 1. Frequency Spectrum of 1kHz Square Wave
Figure 1 shows a plot of a square wave’s harmonics (frequency components) computed and
transmitted to a personal computer by the Model 2015 or 2016. A square wave’s spectral content
consists of only odd harmonics whose magnitudes are (1/harmonic number × the magnitude of
the fundamental). For example, the magnitude of the third harmonic is
1
⁄3the magnitude of the
fundamental.
0.35
0.3
0.25
Ratio to
Fundamental
0.2
0.15
0.1
0.05
0
23456789101112131415161718192021
Harmonic
www.keithley.com
1.888.KEITHLEY (U.S. only)
A GREATER MEASURE OF CONFIDENCE
Audio analyzing and total harmonic distortion DMMs
DIGITAL MULTIMETERS & SYSTEMS
Optimized for Production Testing
The Models 2015, 2015-P, 2016, and 2016-P can perform fast frequency sweeps for characterizing
audio-band circuitry in production test systems. For example, the instruments can execute a single
sweep of 30 frequencies and transmit both rms voltage readings and THD readings to a computer in
only 1.1 seconds. With that data, a complete frequency response analysis and a harmonic distortion
vs. frequency analysis can be performed in a very short time. Thus high speed testing of the audio
performance of a high volume device such as a cellular telephone can be performed without reducing the number of tests or reducing the measurements in each test. With these instruments, which
are optimized for production testing, test engineers can lower test times, in comparison to test
speeds achievable with general purpose audio analyzers, without sacrificing production test quality.
Dual Output Source
The Models 2015, 2015-P, 2016, and 2016-P include an internal audio band sine wave source for generating stimulus signals. A second output, the inverse of the first output, is also available, simplifying
the testing of differential input circuits for common mode or noise cancellation performance.
Figure 2. Total Harmonic Distortion
Analysis and Frequency
Response of a Portable Wireless
Telecommunication Device
Figure 3. THD and 2nd, 3rd, and 4th Harmonics as a Function of Frequency
Figure 4. Frequency Response
Figures 2, 3, and 4 demonstrate how the
Model 2015, 2015-P, 2016, or 2016-P can provide both time domain and frequency domain
measurements in a single test protocol. Figure
2 shows a sample test system schematic with
a telecommunication device in a loop back
mode test. The Audio Analyzing DMM’s source
provides a stimulus frequency sweep, and the
Audio Analyzing DMM measures the response
from the microphone circuit. Figure 3 shows
the resulting frequency domain analysis of the
THD and the first three harmonics as a function of frequency. Figure 4 shows the time
domain analysis of microphone circuit output
voltage as a function of frequency.
2015, 2015-P,
2016, 2016-P
61⁄2-Digit THDMultimeters
61⁄2-Digit Audio Analyzing Multimeters
Ordering Information
2015 Total Harmonic
Distortion 6
1
⁄2-Digit
Multimeter
2015-P Audio Analyzing DMM
2016 Total Harmonic
Distortion 6
1
⁄2-Digit
DMM w/9V Source
Output
2016-P Audio Analyzing DMM
w/9V Source Output
These products are available
with an Extended Warranty.
Accessories Supplied
Model 1751 Safety Test Leads,
User Manual, Service Manual.
Device Under Test
0
–10
–20
–30
–40
Relative
Output
–50
Level
(dB)
–60
–70
–80
–90
–100
100 1000 10000
10
5
Frequency (Hz)
THD:
Levels relative to fundamental:
2nd harmonic
3rd harmonic
4th harmonic
Output
Transducer
Source
Output
Model 2015, 2015-P, 2016, or 2016-P
2015 MULTIMETER
Input
Transducer
Signal
Input
0
Relative
Output
(dB)
–5
–10
–15
–20
100 1000 10000
Frequency (Hz)
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