Sound Card based Test & Measurement System

Almost every PC or Pocket PC have a built-in sound card. Sound cards are usually treated as an audio input and output devices for recording, synthesizing, and replaying speech, music and songs. However, sound cards can do more than that.

From instrumentation and control point of view, a sound Card is a dual-channel A/D and dual-channel D/A device, which has a flat frequency response in audio frequency range and have a sampling rate of up to 192kHz, sampling depth of up to 24 bits. Even without any external attenuation circuit, it is able to measure a signal from down to 1 uV to 1V, thanks to its built-in gain control (like Mic Boost, Mic Volume and Line Volume).

Measurement accuracy depends on its hardware quality. Normally, an internal standalone sound card is better than an on-board sound card (chip), and an external sound card is the best. Professional grade sound card is better than consumer grade sound card. In terms of price, even the professional grade sound card is much cheaper (a few times normally) than its peers in A/D and D/A cards.

Using an external sound card can avoid the interference within the enclosure of the computer casing. A professional sound card can be as good as a professional AD or DA card for test and measurement in audio frequency range. A good article in "Test & Measurement World" (http://www.tmworld.com/article/CA187380.html) has conducted a comparison test between an old 16-bit, Creative Labs Sound Blaster AWE-32 and a 16-bit ADC National Instruments PCI MIO-16XE-10, the result shows that in the THD measurement which requires high precision and accuracy, the results measured by both cards are comparable.

The accuracy of the clock reference is 0.00x% typically for an ordinary sound card. For example, a 0.002%'s inaccuracy in a sampling rate of 44100 Hz means an error of only 0.88Hz. The noise level of a good sound card can be below -110dB, THD below 0.001%.

So, what can be measured by a sound card. Well, it can measure any signal perfectly within audio frequency range, like vibration signal, rotational speed, heat and Lung sound, ECG....., depending on the sensor used, and of course, depending on the software used. A good one can be found at: http://www.virtins.com. It is FREE to download and try.

Product Website: http://www.virtins.com
Download PC version: http://www.virtins.com/MIsetup.exe
Download Pocket PC version: http://www.virtins.com/PocketINSSetup.exe
Video Demo:





Multi-Instrument is a powerful sound card based multi-function virtual instrument software. It features a specially designed data acquisition approach, which is able to monitor the input signal continuously without missing any trigger event before a frame of data is collected. It has a very fast screen refresh rate (typically greater than 50 frames per second). It supports sophisticated triggering method including pre-trigger and post-trigger,level trigger and differential trigger. It Supports 8, 16, 24 bits and multilingual user interface, including English, French, German, Italian, Spanish, Portuguese, Russian, Simplified Chinese, Traditional Chinese, Japanese, and Korean.


A comprehensive range of functions are provided, including:

(1) Oscilloscope
Dual-trace waveform, Waveform addition and subtraction, Lissajous Pattern, transient/long-time signal recording, voltmeter. Various digital filters are supported.


(2) Spectrum Analyzer
RMS amplitude spectrum, relative amplitude spectrum, octave analysis (1/1,1/3,1/6,1/12,1/24), frequency compensation, frequency weighting (A,B,C,ITU-R 468), peak hold, averaging, measurement of THD, THD+N, SNR, SINAD, Noise Level, IMD, Bandwidth and Crosstalk, phase spectrum, auto correlation function, cross correlation function, coherence function, transfer function (Bode plot), impulse response. Support 55 window functions and window overlap.


(3) Signal Generator
Function generation, multitone generation, arbitrary waveform generation, burst tone generation, MLS generation, DTMF generation, musical scale generation, white noise and pink noise generation, and frequency/amplitude sweep.

Synchronized operation between the signal generator and the oscilloscope is supported.


(4) Multimeter
voltmeter, sound pressure level meter(dB, dBA, dBB, dBC), frequency counter, RPM meter, counter, duty cycle meter,
F/V converter. The counter trigger level and hysteresis can be adjusted.


(5) Spectrum 3D Plot
It is used to trace the spectrum variation with time. Two types of plots are provided: waterfall and spectrogram, with adjustable tilt angle of T axis, adjustable height of Y axis, and selectable color palettes.


(6) Data Logger
It provides long time data logging function for 93 derived variables, including RMS value, Peak Frequency, Sound Pressure Level, RPM, THD, etc. Up to eight data logger windows can be opened and each window can trace up to 8 variables. The logged data files can be reloaded into the data logger for review.


(7) LCR meter
It is used to measure the value of an inductor, a capacitor or a resistor, or the impedance of a network of them.


(8) Device Test Plan
Device Test Plan provides a mechanism for you to configure and conduct your own device test steps. It takes the advantage of the sound card's capability of simultaneous input & output, to generate a stimulus to the Device Under Test (DUT) and acquire the response from that device at the same time. Different stimuli can be generated and the response can be analyzed in different ways. It supports 13 instructions with corresponding parameters.


System Requirement

PC or Laptop with 8, 16 or 24 bit Windows compatible sound card, Microsoft Windows95 or greater, Microsoft NT or greater. Screen resolution is recommended to be greater than 800 x 600 pixels.