Daqarta
Data AcQuisition And Real-Time Analysis
Scope - Spectrum - Spectrogram - Signal Generator
Software for Windows
Science with your Sound Card!
The following is from the Daqarta Help system:

Features:

Oscilloscope

Spectrum Analyzer

8-Channel
Signal Generator

(Absolutely FREE!)

Spectrogram

Pitch Tracker

Pitch-to-MIDI

DaqMusiq Generator
(Free Music... Forever!)

Engine Simulator

LCR Meter

Remote Operation

DC Measurements

True RMS Voltmeter

Sound Level Meter

Frequency Counter
    Period
    Event
    Spectral Event

    Temperature
    Pressure
    MHz Frequencies

Data Logger

Waveform Averager

Histogram

Post-Stimulus Time
Histogram (PSTH)

THD Meter

IMD Meter

Precision Phase Meter

Pulse Meter

Macro System

Multi-Trace Arrays

Trigger Controls

Auto-Calibration

Spectral Peak Track

Spectrum Limit Testing

Direct-to-Disk Recording

Accessibility

Applications:

Frequency response

Distortion measurement

Speech and music

Microphone calibration

Loudspeaker test

Auditory phenomena

Musical instrument tuning

Animal sound

Evoked potentials

Rotating machinery

Automotive

Product test

Contact us about
your application!

Isolation, Electrical

WHENEVER ELECTRICAL EQUIPMENT IS CONNECTED TO A LIVING SUBJECT THERE IS A DANGER OF ELECTROCUTION due to malfunction. To minimize this risk, all connections to the subject should be electrically isolated from the main power lines, including the ground or neutral line. This means that there must be no electrical path between the subject and the line.

Optical isolation is usually the method of choice: If the device being connected to the subject is a monitoring or recording amplifier, for example, it is battery-operated so that no connection to the main power lines is needed. The isolator then converts the amplified signal from electrical to optical form, essentially by using it to drive a special Light Emitting Diode (LED) similar to those commonly used as indicator lights. The light is modulated so that its intensity is directly proportional to the signal amplitude.

The light then travels a short distance through an electrical insulator (epoxy plastic, for example) before hitting a linear photodetector that converts it back to electrical form. The detector part of the circuit is run from the main power lines, but is not connected electrically to the LED side (subject side) of the circuit in any way.

This maintains total electrical isolation of the subject from the power lines in the event of catastrophic failure of the equipment or the power system itself.

For electrical stimulation of the subject, the idea is the same but reversed: Here the stimulator must be driven by batteries, and receives a light signal from a powerline-driven modulator. (See "LED Flasher / Modulator" under DC Pulse Output Circuits.)

Although the isolator assures safety from powerline problems, the battery-powered amplifier or stimulator must still be carefully designed: Even small electrical currents can be lethal when directly connected to the subject, especially across the heart as in recording heart rate, etc.

For use on human subjects, always use properly designed and isolated equipment certified for the intended purpose. For small lab animals like rats, mice, and guinea pigs, however, the danger is usually considered minimal enough to use "home-made" preamplifiers without isolation. Consult the animal use committee at your institution for details.

An alternative isolation method for home or experimental use is to use a laptop computer that is running entirely from its internal battery; it must be completely disconnected from mains power, and from any other equipment (such as external disk drives or power amplifiers) that may be connected to mains power. The laptop is thus completely isolated from the power lines. You can then connect battery powered preamplifiers or stimulators directly to the laptop, and to your subject. Although providing excellent isolation, this method can suffer from limited battery life of the laptop.


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