Data AcQuisition And Real-Time AnalysisScope - Spectrum - Spectrogram - Signal Generator
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User Line Units/Volt
If the selected User Line does not use a .CAL or .FRD file, this control allows you to specify the conversion factor that Daqarta must apply to the raw voltage values in order to display them in your chosen User Units.
The Units/Volt value is usually supplied as a calibration factor when you purchase a transducer. It may be supplied as Volts/Unit, in which case you need to enter the reciprocal of the value here.
For example, a force transducer may be calibrated such that when a Newton of force is applied, the transducer output is 1.234 mV. The value you should enter is thus 1 / 0.001234 or 810.3728 Newtons/volt.
If the value to be entered is very large or small, use a size prefix directly in the value entry, never in the name field. Daqarta will always show the value with a convenient prefix, such as '1.00000p' for 1 pico-unit. Do not enter 1.000 here with a 'p' prefix in the name field.
When Y-log Spectrum mode is active, this control will change to dB relative to 1 Unit/Volt (indicated as dB:Units/V). For example, 2.0000 Units/V will become 6.0206 dB:Units/V. You may find this mode more convenient for entering microphone or speaker sensitivities.
If the line uses a .CAL or .FRD file, the Units/Volt control will be disabled but will show the baseline value from the file. This is the value that will be used with waveform and linear Spectrum displays, which don't support the frequency-dependent calibration that Y-log Spectrum does. In those modes, the trace or cursor readout values are only approximate.
If the relevant User Line dialog is open, UserFactor=1.234 will set 1.234 User Units per Volt.
However, it is usually more useful for a macro to change User Line controls directly, without the dialog open. This requires that you use Uxx. prefixes before the macro command to specify which line the macro refers to, as in U0L.UserFactor=1.234.
U0L. through U7R. specify Input lines 0-7 and the Left or Right channel of each.
If your card has only Master Input lines, UIL. or UIR. prefixes will specify them here.
If your card has only Master Output lines, specify them with UOL. or UOR. prefixes.
Otherwise, UWL. and UWR. prefixes specify Wave Out lines.
If a data file is open, UIL. and UIR. prefixes specify Left and Right Input lines, while UOL. and UOR. specify Output lines.
If Y-log Spectrum is active the same basic UserFactor=1.234 command will set +1.234 dB, so your macros should make sure the desired mode is set ahead of time.
Note that in this dB mode the Factor values may be positive or negative. U0L.UserFactor=U0L.UserFactor - 1 will make the Factor more negative by 1 dB.
UserFactor?0 is a read-only variable that returns the current factor, in dB, for channel 0. You may use channels 0-3 here, given as a single digit. Alternatively, you can use V to specify the current Ch Channel Select number. A default factor of 1.00 is returned for a channel number outside the 0-3 range, whether specified directly or via the V option.
0 = Left In 1 = Right In 2 = Left Out 3 = Right Out V = Ch value (0-3)
The return value is always in dB, regardless of display mode. For example, 0 dB is equivalent to a linear factor of x1.00, +20 dB is x10.00, and -20 dB is x0.100.
For input channels 0 or 1 the return value takes into account whether your sound card has separate input lines and if so which one is selected. Likewise, for output channels 2 or 3 it considers whether the sound card has separate Wave controls or uses only Master volume.
See Macro Data Unit Conversions for a discussion of how to use this variable together with others to obtain actual volts or User Units from ADC or DAC values returned by certain macro math and macro array functions.
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