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!

Non-Duplex Calibration

Controls: Calibration Menu >> Auto-Calibrate

Some older sound cards, especially those built into older laptops, don't allow simultaneous input and output operation. In that case, Daqarta will show the Wave Out and Duplex Delay lines disabled in the Auto-Calibration dialog. You may still be able to use Auto-Calibration on these cards, but only to calibrate the input lines.

The first thing to try is selecting Synth Out instead of the disabled Wave Out. Since the Synth is unrelated to the wave functions, the card may be able to run it along with wave input. Daqarta will then use that as the signal and measure input levels as usual. This is not always satisfactory since Synth sounds are not completely standardized: Daqarta sets the sound to Ocarina, which is a steady sine wave on the Microsoft GS Wavetable synth that is used with most modern sound cards. But it may be neither steady nor a sine wave on an older card with a hardware synth. It may overload the input, but Daqarta won't be able to tell since it may look "distorted" naturally.

A bigger problem is that these non-duplex cards typically only allow Synth Out to appear on Synth Input in this case, and don't produce any sound on the output. You may be able to calibrate the Synth Input, and possibly Master Input, but that won't be very useful since you can't use Synth Input for anything else.

If you have access to an external test oscillator or signal generator, you can connect it to the input lines and select Ext Source. Since Daqarta can't control that source, before you start Auto-Calibration you should set it to produce a sine wave at around 2 kHz, and with the connected input line level control set to 0 (maximum sensitivity) adjust the source level so the input is not distorted. You can tell that by watching the waveform for obvious distortion, but a more sensitive test is to view the spectrum and watch for a sudden increase in harmonic peaks at the onset of distortion.

If you don't have a lab-type source, you can run Daqarta on another computer and just use the Generator output. That will allow you to calibrate the input lines.

Calibrating the output lines on non-duplex cards is more work, since there is no automation. You can use the manual methods provided in the Generator Attenuator Options to calibrate Wave Out and Master Out.

If you have another computer running Daqarta, you can use it like a precision voltmeter to do the manual calibration. You can do this even if the other card is not calibrated, as long as you only use a single input range on that card. It can even be another non-duplex system. All you need is for it to be able to measure relative voltage changes. Set it to linear (not Y-log) Spectrum mode and put a cursor on the peak of the signal coming from the system being calibrated. Then record the cursor readout value at each volume step in Meter mode of the target system Wave or Master calibration dialog.

Once Wave and Master Out are calibrated, you can toggle Use dB on and the Generator volume controls will be in dB instead of arbitrary step numbers. Likewise, when the Input lines and Master In are calibrated, the dB Toggle button will allow dB controls for Line Levels and Master Levels.

NOTE: The Auto-Calibration dialog is not available after the trial period, unless a paid license key is present.


See also Auto-Calibrate Dialog, Saving the Calibration, Calibration Overview

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