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Data Zero Manual Null Buttons

Controls: Zero Dialog >> Manual >> Null
Macros: Ch.ZeroNull, LI.ZeroNull, etc.

The Null buttons are used in Data Zero Manual mode to set the true zero position on a DC-coupled measurement system. When you press the button, the Manual Adjust value is automatically set to the current average value for that channel, as determined by averaging 1024 samples.

The units shown will be in percent of full scale, or volts (or User Units), depending on the state of the Units button on the right. You can toggle Units at any time.

To use the Null buttons, you first set the external measuring system to produce an effective zero input condition on a channel. This may involve venting a relative pressure sensor to atmosphere, putting a thermocouple into an ice bath (or into thermal contact with the reference temperature), or shorting the input leads of a voltmeter circuit. When you have done this, whatever DC level is read by the ADC must be treated as the effective zero, even if it is not zero volts. Hitting the Null button for that channel will do this automatically.

Macro Notes:

LI.ZeroNull=1 nulls the Left Input channel. The null operation takes place no matter what value you supply in the macro, including 0.

Similarly, RI.ZeroNull nulls the Right Input, LO.ZeroNull nulls the Left Output, and RO.ZeroNull nulls the Right Output.

Alternatively, you can use the Ch. prefix to null a channel previously specified via the Ch Channel Select command.

Note that attempts to use these commands when the controls are disabled in Spectrum, Spectrogram, or Pitch Track modes will result in "Control disabled. Aborting macro." You can check if this control is enabled via an E.IF.ZeroNull= control enable IF test. You don't need to specify the channel, since all are enabled or disabled together.

See also Zero (Cursor, Average, Peak, or Manual)


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