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:



Spectrum Analyzer

Signal Generator

(Absolutely FREE!)


Pitch Tracker


DaqMusiq Generator
(Free Music... Forever!)

Engine Simulator

LCR Meter

Remote Operation

DC Measurements

True RMS Voltmeter

Sound Level Meter

Frequency Counter
    Spectral Event

    MHz Frequencies

Data Logger

Waveform Averager


Post-Stimulus Time
Histogram (PSTH)

THD Meter

IMD Meter

Precision Phase Meter

Pulse Meter

Macro System

Multi-Trace Arrays

Trigger Controls


Spectral Peak Track

Spectrum Limit Testing

Direct-to-Disk Recording



Frequency response

Distortion measurement

Speech and music

Microphone calibration

Loudspeaker test

Auditory phenomena

Musical instrument tuning

Animal sound

Evoked potentials

Rotating machinery


Product test

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your application!

User Units Dialog

Controls: Calibration Menu >> User Units
Macros: UnitsDlg, UserUnits

Daqarta can be calibrated to show units other than the default Volts. Each channel of each line may have its own User Units, with its own calibration. Calibrations may be simple factors or (in Y-log Spectrum mode only) complete frequency response curves. For example, you can supply microphone calibration curves to enable Daqarta to show input signals directly in dB SPL; you can also use Daqarta to create calibration curves to show speaker outputs in SPL.

The control center for all these options is the User Units dialog. It can be invoked from the Calibration menu (ALT+C, U) or directly via CTRL+U. It has columns of Left and Right buttons for each line on your sound card. Each button opens a User Line dialog that allows you to enter the calibration details for that line and channel, and to enable or disable that calibration.

NOTE that for live operation you can only apply User calibration to lines with calibrated mixer steps (such as by Auto-Calibrate). Otherwise, Daqarta would have no way to know the proper scaling to apply to any setting other than full-scale.

User Units information is stored in the Daqarta0.USR file that is loaded when Daqarta starts. If you make any changes to these values, you will be prompted to save them when you exit Daqarta. If your system has more than one card (which you can select via the Device controls in the Start Preferences dialog), then the files may be called Daqarta1.USR, etc. Note that the Output Device number is used here. The Input Device number is usually (but not always) the same.

The Daqartan value may also be changed via shortcut command-line parameters for use with multiple desktop icons when managing multiple devices.

At the top of the User Units dialog is a large "Use Enabled Units" button that tells Daqarta to apply the specified calibrations to the enabled lines. You can toggle this at any time via ALT+U. Since it only toggles enabled lines, you can choose to use custom units for some lines, and leave others at Volts. For convenience, there is also a redundant copy of this button in each User Line dialog.

The User Units dialog applies to live data. When a .DQA file is open, the File Units dialog will appear in its place. It only has 4 buttons, one for each possible channel in the file, and any of those that weren't actually recorded will be disabled. Otherwise, it behaves like the normal User Units dialog: You can open a User Line dialog that allows you to change the User calibration or add it to the file. You can then save the file with this new User calibration.

Note that for file data, only User calibration can be changed, not the basic Range or External Gain factors. (Those dialogs are disabled when a file is open.) The .DQA file stores absolute voltage calibration separately from User Units/Volt factors and names, and calibration curves. You can change only the User portions.

The assumption here is that the sound card Ranges (and hopefully any External Gain amplification) are not variable, so Daqarta can store data that can always be converted to absolute volts. But it is quite common for system calibration to change, even during the experiment, due to factors that are hard to control.

For example, a sound delivery tube for small animals may become partly obstructed with earwax during the experiment. You have the pre-experiment calibration curve for the unobstructed tube, and you can obtain a calibration curve for the obstructed tube after the experiment. If you know when the obstruction occurred, you can go back and correct only those files recorded after that point. If you don't know exactly when, you may want to compare results with both calibrations and see how big the difference is, and adjust your experimental uncertainty accordingly.

What if, after the experiment, you discover that your assistant had previously changed the gain on your external amplifier, so that it was different from the External Gain setting of the file? In that case, you may want to manually compensate by adjusting the User Units/Volt appropriately. (If you were using a calibration curve on that line, you may need to edit the reference in the file.)

If the file is a .DQA type created on a calibrated system, the file itself contains any relevant range calibration information from the system it was recorded on, independent of the system used for later analysis. In this case (unlike for live data) you can apply User calibration even if the card on the analysis system is not calibrated.

Note that if the file was created on an uncalibrated system (or uses .WAV or .DAT format that can't hold calibration information) the top of the Y axis will show 'Uncal'. If you somehow know the proper calibration, you can apply is as a User calibration and re-save the file as a .DQA type. When you later open that file it will still show 'Uncal', but when User Units is active you will see whatever User calibration you applied.

Macro Notes:

UnitsDlg=1 opens the User Units dialog, UnitsDlg=0 closes it, and UnitsDlg=x toggles between open and closed. If a file is open, this same command applies to the File Units dialog.

See Macro Notes under User Line Dialog for how to open the individual dialogs corresponding to each Line button shown in the User Units or File Units dialog.

UserUnits=1 applies the units you have enabled in the User Line Dialog. UserUnits=0 restores default Volts units and scaling, and UserUnits=x toggles between User and default.


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