IviScope Fetch Waveform Measurement
IviScopeWaveformMeas Capability Group [WM]
This VI fetches a waveform measurement from the channel you specify. If the channel is not enabled for the acquisition, this VI returns the IVISCOPE_ERROR_CHANNEL_NOT_ENABLED error.
The waveform on which the oscilloscope calculates the waveform measurement is from an acquisition that you previously initiated.
Use the IviScope Initiate Acquisition VI to start an acquisition on the channels that you enable with the IviScope Configure Channel VI. The oscilloscope acquires waveforms for the enabled channels concurrently. You use the IviScope Acquisition Status VI to determine when the acquisition is complete. You call this VI separately for each waveform measurement you want to obtain on a specific channel.
You can call the IviScope Read Waveform Measurement [WM] VI instead of the IviScope Initiate Acquisition VI. The IviScope Read Waveform Measurement [WM] VI starts an acquisition on all enabled channels. It then waits for the acquisition to complete, obtains a waveform measurement on the channel you specify, and returns the measurement value. You call this VI separately for any other waveform measurement that you want to obtain on a specific channel.
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Notes
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instrument handle The instrument handle that you obtain from the IviScope Initialize or the IviScope Initialize With Options VI. |
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channel name Pass the virtual channel name that you assign to the instrument in MAX from which you want to fetch a waveform measurement.
Virtual channel names are aliases for instrument specific channel strings. The instrument specific channel strings can differ from one instrument to another. Virtual channel names allow you to use and swap instruments without having to change the channel names in your source code. You assign a virtual channel name to an instrument specific channel through MAX. This control accepts virtual channel names you have assigned to the specific instrument you are using. It also accepts the instrument specific channel names. Default Value: "CHANNEL1" |
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measurement function Pass the waveform measurement you want the oscilloscope to perform.
Defined values: IVISCOPE_VAL_RISE_TIME—Rise Time IVISCOPE_VAL_FALL_TIME—Fall Time IVISCOPE_VAL_FREQUENCY—Frequency IVISCOPE_VAL_PERIOD—Period IVISCOPE_VAL_VOLTAGE_RMS—Voltage RMS IVISCOPE_VAL_VOLTAGE_CYCLE_RMS—Voltage RMS (Cycle) IVISCOPE_VAL_VOLTAGE_MAX—Voltage Max IVISCOPE_VAL_VOLTAGE_MIN—Voltage Min IVISCOPE_VAL_VOLTAGE_PEAK_TO_PEAK—Voltage Vpp IVISCOPE_VAL_VOLTAGE_HIGH—Voltage High IVISCOPE_VAL_VOLTAGE_LOW—Voltage Low IVISCOPE_VAL_VOLTAGE_AVERAGE—Voltage Avg. IVISCOPE_VAL_VOLTAGE_CYCLE_AVERAGE—Voltage Avg. (Cycle) IVISCOPE_VAL_WIDTH_NEG—Width Negative IVISCOPE_VAL_WIDTH_POS—Width Positive IVISCOPE_VAL_DUTY_CYCLE_NEG—Duty Cycle Negative Duty Cycle Negative = 100.0 x (Width Negative)/Period IVISCOPE_VAL_DUTY_CYCLE_POS—Duty Cycle Positive Duty Cycle Positive = 100.0 X (Width Positive)/Period IVISCOPE_VAL_AMPLITUDE—Amplitude IVISCOPE_VAL_OVERSHOOT—Overshoot OVERSHOOT = ((local maximum - Voltage High)/Amplitude)*100% where the local maximum is the maximum voltage of the signal in the first half of the time period that commences when the rising edge crosses the high reference level and concludes when the subsequent falling edge crosses the high reference level. For the falling edge: OVERSHOOT = ((Voltage Low - local minimum)/Amplitude)*100% where the local minimum is the minimum value of the signal measured in the first half of the time period that commences when the falling edge crosses the low reference level and concludes when the subsequent rising edge crosses the low reference level. The instrument makes the measurement on the edge closest to the beginning of the waveform record. IVISCOPE_VAL_PRESHOOT—Preshoot For the rising edge: For the falling edge: Default Value: IVISCOPE_VAL_RISE_TIME |
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Note You must configure the appropriate reference levels before you call this VI. You configure the low, mid, and high references either by calling the IviScope Configure Reference Levels [WM] VI or by setting the following properties: IviScope Measurement High Reference [WM] IviScope Measurement Low Reference [WM] IviScope Measurement Mid Reference [WM] |
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error in (no error) The error in cluster can accept error information wired from VIs previously called. Use this information to decide if any functionality should be bypassed in the event of errors from other VIs.
The pop-up option Explain Error (or Explain Warning) gives more information about the error displayed. |
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instrument handle out The instrument handle that you obtain from the IviScope Initialize or the IviScope Initialize With Options VI. |
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measurement Returns the measured value.
Units: The units depend on the Measurement Function you select, as shown below. Rise Time—seconds Fall Time—seconds Frequency—hertz Period—seconds Voltage RMS—volts Voltage RMS (Cycle)—volts Voltage Max—volts Voltage Min—volts Voltage Vpp—volts Voltage High—volts Voltage Low—volts Voltage Avg.—volts Voltage Avg. (Cycle)—volts Width Negative—seconds Width Positive—seconds Duty Cycle Negative—percentage Duty Cycle Positive—percentage Amplitude—volts Overshoot—percentage Preshoot—percentage |
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error out The error out cluster passes error or warning information out of a VI to be used by other VIs.
The pop-up option Explain Error (or Explain Warning) gives more information about the error displayed. |