Oscilloscope: The screenshot shows that the waveform trigger point is right at the upward 0.2 V (Trigger Edge =Up, Trigger Level=20%). The refresh time of the data was measured to be 15 frames/second.

Spectrum Analyzer: It is in Relative Amplitude Spectrum Mode with both X and Y axes in linear scale. The peak frequency measured was 991 Hz. The measurement error of 9 Hz is within the FFT frequency resolution dictated by the equation: (Sampling Frequency)/(FFT Size)=44100/1024=43 (Hz). The frequency resolution can be improved by increasing the FFT size. Note that although decreasing the sampling frequency can improve the frequency resolution, the highest frequency that can be measured will also be decreased which in turn may cause the spectral aliasing problem. Decreasing sampling frequency can be used only if you are very sure that the highest frequency in the signal under test is below half of the sampling frequency (Nyquist Sampling Theorem).

Spectrum Analyzer: The three frequency peaks are displayed correctly at 1kHz, 2kHz and 4kHz.

Signal Generator: The signal was generated using the multi-tone function of the Signal Generator.

Spectrum Analyzer: It indicates that a 1 kHz square wave consists of a fundamental frequency of 1 kHz and a series of odd harmonics, e.g. 3 kHz, 5 kHz, 7 kHz…. The amplitude of harmonics decreases very fast (in the ratio 1/N) as the frequency goes up.

Demo 6: 500 Hz triangle wave generation and measurement triggered at downward -0.3 V

Spectrum Analyzer: It indicates that a 500 Hz triangle wave consists of a fundamental frequency of 500 Hz and a series of odd harmonics, e.g. 1500 Hz, 2500 Hz, 3500 Hz…. The amplitude of harmonics decreases more rapidly than that of a square wave (in the ratio 1/N²) as the frequency goes up.

Spectrum Analyzer: It indicates that a 2 kHz saw tooth wave consists of a fundamental frequency of 2 kHz and a series of harmonics, e.g. 4 kHz, 6 kHz, 8 kHz…. The amplitude of harmonics decreases quite slowly (in the ratio 1/N) as the frequency goes up.

Spectrum Analyzer: It indicates that a 1 kHz "Heartbeat" wave consists of a series of frequency peaks at 1 kHz, 2 kHz, 3 kHz, 4 kHz, …. with the highest peak at 2 kHz.

Signal Generator: The "Hearbeat" wave was generated via the waveform library heartbeat.wfl supplied together with the software. It is simply a TXT file containing the coordinates of each points in a period of the waveform. The waveform library can be easily created by users. There is no need to specify the frequency of the waveform in the WFL file. The user-defined waveform can be generated later at any frequency allowed by the Signal Generator.

Multi-Instrument can be used as an assistant tool in teaching wave-related or sound-related science and physics in primary schools, middle schools and high schools, electronic-signal-related topics in vocational schools, and DSP subject in universities. It can also be used in laboratories in place of those much more expensive instruments such as digital storage oscilloscope, spectrum analyzer, signal generator and frequency counter, etc. You can also use Pocket Multi-Instrument if your class room is equipped with a projector.

A laptop or pocket PC without any additional accessories and wires is enough for demonstration in a class if you do not intend to measure actual electronic signals.  You can generate the desired signals and see their waveforms and spectra within the software. This can be done by either selecting the "Display in Oscilloscope" option in the Signal Generator or Choosing "Wave Out Mix" as the input device in the Recording Control under Window Control Panel. 

Application Note 1:  MP3 Encoding Quality and Nyquist-Shannon Sampling Theorem

Take a look here http://gwailly.free.fr/leisure/MP3/MP3_encoding2.html to see how  Georges de Wailly explained MP3 Encoding Quality and Nyquist-Shannon Sampling Theorem with the help of Multi-Instrument.

Scientific research normally requires flexibility in choosing measuring parameters and capability to view a single data point out of thousands of data points acquired , when necessary.  Multi-Instrument is well designed to carter for these needs. 

Application Note 1: Extremely Low Frequency Radio Emission from Flying Insects

In 2005, Walton C, Koemel used the tune radio frequency (TRF) receiver (20~18,000Hz) developed by Walton C. Koemel and Philip S. Callahan ("Relationship of Extremely Low Frequency Radio Emission from Flying Insects to Semiochemical Communication", Annals of The Entomological Society of America, Vol. 87, No. 5, pp. 491-497, 1994) together with Multi-Instrument to investigate the extremely low frequency radio emission from flying insects such as European honey bee, African honey bee, Mosquito, etc. 

The screenshot shows the radio emission signal received from a European honey bee.  When you see a peak that has a smaller peak on the side, the taller peak is produced by the wing closer to the TRF radio receiver antenna. The smaller peak is produced by the wing farther away.  In this case, the wings are almost in phase with each other.  When you see a series of tall peaks with short peaks in between, the wings are almost 180 degrees out of phase with each other. You can also see how the wing-beat frequency changes from wing-beat to wing-beat.  

(Courtesy of Walton C, Koemel, Texas, USA)

Any sensors or probes that output signals within audio frequency range can be connected to a PC or Pocket PC's audio channels with or without a pre-amplifier or an attenuator.  Multi-Instrument and Pocket Multi-Instrument are useful tools in vibration analysis, earthquake wave measurement, rock density measurement, power quality, etc.  It is very hardy especially when you are at site. See an application by Turbomagnetics Research Associates, Santa Cruz, California, USA.

Multi-Instrument and Pocket Multi-Instrument can be used to measure sound pressure level, analyzer noises, adjust an audio system, etc.  

Multi-Instrument and Pocket Multi-Instrument can replace oscilloscope, spectrum analyzer, signal generator, multimeter, network analyzer to measure electronic circuits within the audio frequency range. With the capability to run multiple instruments simultaneously, it can be use to measure the characteristics of a device under test (DUT) such as frequency response and impedance.

Application Note 1: Sherlock In The XP Age 

By Malcolm C. Mallette, WA9BVS, published in CQ VHF winter 2006 issue. (see introduction in the magazine)

In this article, Malcolm C. Mallette presented a new "Sherlock" transmitter fingerprint system which used VIRTINS Sound Card Oscilloscope together with a FM receiver to identify transmitters by their turn-on and turn-off fingerprint. 

When the microphone button of a transmitter is pressed, during the first two-tenths of a second, the transmitter moves in a pattern around the operating frequency, as the phase locked loop locks up. That is what is meant by the turn-on characteristic (or fingerprint) of a transmitter. Similar movements in frequency when the transmitter is turned off are referred to as the turn-off characteristic (or fingerprint).  To capture a transmitter’s turn-on and turn-off fingerprints, the software must capture the frequency movements of the transmitter in the two-tenths of a second when it turns on or off

He demonstrated that with VIRTINS Sound Card Oscilloscope connected to the output of the detector in a FM receiver, he was able to capture and save the transient turn-on and turn-off fingerprints of  a transmitter. The screenshot shows 10 seconds of reception, with typical noise for the first 3 seconds, followed by a few seconds of a received transmission, then noise again.

(Courtesy of CQ Communications, Inc)

You can use Multi-Instrument and Pocket Multi-Instrument to tune your musical instrument with high accuracy. Be sure to set the scan time, FFT size and sampling frequency properly to achieve high frequency resolution.  We recommend a scan time of 500 ms, a FFT size of of 32768 and a sampling frequency of 44100 Hz for musical instrument calibration. The resulting frequency resolution is about 1.3 Hz.

Biomedical signals normally have frequencies within audio frequency range, e.g. electrocardiogram (ECG/EKG), lung and heart sound, etc. Multi-Instrument and Pocket Multi-Instrument can be used to capture and display these biomedical signals to the doctor at real time for diagnosis. The data can be saved for later reference.