Data AcQuisition And Real-Time Analysis
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The following is from the Daqarta Help system:



Spectrum Analyzer

Signal Generator

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Pitch Tracker


DaqMusiq Generator
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Engine Simulator

LCR Meter

Remote Operation

DC Measurements

True RMS Voltmeter

Sound Level Meter

Frequency Counter
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Data Logger

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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

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DDisk Write Size Preset

Controls: DDisk Dialog >> Write Size Preset
Macro: DDiskPreset

Rather than ending a DDisk recording manually, this control lets you set a predetermined size. The recording will stop automatically when it reaches this size, although you can still stop it manually at any time before that using the Record button or INSert key and/or ALT+D.

The default units for this control are Samples, where one sample means one sample per active channel; alternatively, think of one sample as one time point or sample period, where all channels are sampled simultaneously. So two files with the same number of samples could differ by a factor of 2 or 4 in the number of bytes.

You can use the DDisk Units control in this same dialog to toggle the units among Bytes, Samples, Seconds, or time in HH:MM:SS format. (Local or UTC Time modes only apply when reading a file; HH:MM:SS will be substituted.)

The maximum size limit is dictated by the .WAV (and hence .DQA) format at just under 4 GB. It is further constrained by the number of active channels, since each channel requires two bytes per sample. If only one channel is active, the limit is over 2 billion samples, or more than 12 hours at 48000 Hz sample rate. With 2 channels, it is over 6 hours and with 4 channels (or 3) it is over 3 hours.

If you set Size Preset to a high value and then increase the number of channels, when you start DDisk you may be prompted to let Daqarta adjust the value to keep it within the format limits. If you would prefer to set some other limit yourself, ESCape or Cancel that prompt to exit DDisk, adjust the value from the CTRL+D dialog, and start DDisk again.

Setting Write Size Preset to 0 disables it and requires that you end recording manually. However, Daqarta will monitor remaining disk space during the recording, and end it automatically if needed to maintain about 1 MB of reserve space.

There is a minimum active Preset size of 1024 samples, since that is the smallest number of samples that Daqarta can display. If you try to set any value greater than zero but less than 1024, it will be forced to 1024.

Macro Notes:

The DDiskPreset macro uses the units (Bytes, Samples, or Seconds) set via the Units buttons in the DDisk Controls dialog. HH:MM:SS mode is treated as Seconds here. So depending on the Units, DDiskPreset=100k will set the limit to 100000 bytes, samples, or seconds. (Local or UTC Time modes only apply when reading a file; HH:MM:SS will be substituted.)

See also Direct-To-Disk (DDisk) Toggle, DDisk Controls Dialog


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