NI-DMM/Switch Express

niDMM VIs

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NI-DMM/Switch Express

Configures and acquires a signal using NI-DMM with National Instruments digital multimeters (DMMs) and PXI or SCXI switch modules.

Note  NI 4050 and NI 4060 DMMs are not supported.

When you place this Express VI on the block diagram, the NI-DMM/Switch Express configuration page opens. To edit an existing configuration, double-click the NI-DMM/Switch Express VI.

Dialog Box Options
Block Diagram Inputs
Block Diagram Outputs
Examples

Dialog Box Options

ParameterDescription
Data Displays the measurement, formatted according to the function, range, and resolution.
Resolution string Displays the absolute resolution.
Table data Displays the measurement(s) per channel, formatted according to the function, range, and resolution. The first column lists the channel(s) being scanned, and the second column lists the last measured sample from the associated channel.
Chart data Displays the measurements per channel.
Autoscale Scales the amplitude axis of the chart. The default value is True.
View as chart Specifies if the chart indicator is visible. Contains the following options:
  • True—The chart indicator is visible.
  • False (default)—The chart indicator is not visible. The numeric indicator is visible when no switch modules are added to the Switch devices list. The table indicator is visible when some switch modules are added.
Configuration Contains the following options:
  • Device—Contains the resource name of the device.
  • Basic Parameters—Contains the following options:
    • Measurement function—Specifies the measurement function used to acquire the measurement. Refer to the Devices section of the NI Digital Multimeters Help at ni.com/manuals for a list of valid ranges. The default value is DC Volts.
    • Range method—Specifies whether auto range is used. Contains the following options:
      • Auto Range—Performs an auto range before acquiring the measurement.
      • Specify Range (default)—Sets the range to the present Auto Range value and uses this range for all subsequent measurements until the measurement configuration is changed.
    • Range value—Sets the range for the present measurement. The default value changes with the selected Measurement function. Range values are coerced up to the closest input range. Refer to the Devices section of the NI Digital Multimeters Help at ni.com/manuals for a list of valid ranges.
    • Range units—Displays the units for the present measurement.
    • Resolution digits—Sets the digits of resolution of the measurement. Resolution cannot be selected when you are auto ranging for frequency and period measurements on the DMM or for capacitance and inductance measurements on the NI 4072. To achieve better resolution for such measurements, use Measurements to average. The default value is 6.5 digits.
    • Measurements to average—Specifies the number of LC measurements that are averaged to produce one reading. The default value is 10.
  • Powerline frequency—Specifies the powerline frequency in hertz. The default value is 60 Hz.
  • Measurement-specific parameters—
    • Auto Zero—Specifies the Auto Zero mode.
      • Auto (default)—NI-DMM selects the Auto Zero setting based upon the configured Measurement function and resolution.
      • Off—Disables Auto Zero.
      • On—The DMM internally disconnects the input signal following each measurement and takes a zero reading. It then subtracts the zero reading from the preceding reading.
        Note Note  For NI 4065 devices, Auto Zero is always ON. Auto Zero is an integral part of the signal measurement phase and adds no extra time to the overall measurement.
    • ADC calibration—Specifies the ADC calibration setting.
      • Auto (default)—The DMM enables or disables ADC calibration based upon the configured Measurement function and resolution.
      • Off—The DMM does not compensate for changes to the gain.
      • On—The DMM measures an internal reference to calculate the correct gain for the measurement.
    • Min frequency (Hz)—Specifies the minimum expected frequency component of the input signal in hertz. This parameter affects the DMM only when you set Measurement function to AC measurements. NI-DMM uses this parameter to calculate the proper aperture for the measurement. The default value is 20.0.
    • Offset compensated ohms—Enables or disables offset compensated ohms.
      Note Note  The NI 4065 is not supported.
      • Off (default)—Disables offset compensated ohms.
      • On—Enables offset compensated ohms.
    • Current source—Specifies the current source provided during diode measurements. Refer to the Devices section of the NI Digital Multimeters Help at ni.com/manuals for valid ranges. The default value is 1 mA.
    • Frequency voltage range method—Specifies whether the frequency voltage auto range is used.
      • Auto Range (default)—Configures the DMM to take an auto range measurement to calculate the voltage range before each frequency or period measurement.
      • Specify Range—Disables auto ranging. NI-DMM sets the voltage range to the last calculated voltage range.
    • Frequency voltage range value—Sets the expected maximum amplitude of the input signal. The minimum peak-to-peak signal amplitude that can be detected is 10% of the specified voltage range. Refer to the Devices section of the NI Digital Multimeters Help at ni.com/manuals for valid ranges. The default value is 50  V.
    • Frequency voltage range units—Displays the volts units for frequency and period measurements.
    • Cable compensation type—Specifies the type of cable compensation that is used for the present range.
      • None (default)—No cable compensation.
      • Open—Open cable compensation.
      • Short—Short cable compensation.
      • Open and Short—Open and short cable compensation.
    • Perform cable compensation—Performs cable compensation of the specified type and returns the corresponding parameters. The default value is False.
    • Conductance—Specifies the active part (conductance) of the open cable compensation. The valid range is any real number >0. The default value, NaN, indicates that compensation has not taken place. If you change the range after performing the cable compensation, you may have to perform it again to obtain the compensation parameters for the present range.
    • Susceptance—Specifies the reactive part (susceptance) of the open cable compensation. The valid range is any real number >0. The default value, NaN, indicates that compensation has not taken place. If you change the range after performing the cable compensation, you may have to perform it again to obtain the compensation parameters for the present range.
    • Resistance—Represents the active part (resistance) of the short cable compensation. The valid range is any real number >0. The default value, NaN, indicates that compensation has not taken place. If you change the range after performing the cable compensation, you may have to perform it again to obtain the compensation parameters for the present range.
    • Reactance—Represents the reactive part (reactance) of the short cable compensation. The valid range is any real number >0. The default value, NaN, indicates that compensation has not taken place. If you change the range after performing the cable compensation, you may have to perform it again to obtain the compensation parameters for the present range.
Timing Contains the following options:
  • Acquire—Configures the Acquisition mode.
    • 1 Sample (default)—Configures a single-point acquisition.
    • N Samples—Configures a finite multipoint acquisition.
    • Continuous—Configures a continuous multipoint acquisition.
  • Samples per channel—Sets the number of measurements the DMM makes in each measurement sequence initiated by a sample trigger. Measurements are taken in an interleaved fashion. For example, if you set Samples per channel to 2 and scan three channels (ch0, ch1, and ch2), the NI-DMM/Switch Express VI returns one reading from each channel in the following order: ch0, ch1, ch2, ch0, ch1, ch2. The maximum number of measurements for a finite acquisition is (number of channels) x (Samples per channel). For continuous acquisitions, up to 100,000 points can be returned at once. The default value is 1.
  • Max time (s)—Specifies the maximum time in seconds allowed for the VI to complete acquisition. If the acquisition does not complete within this time interval, the timeout error is returned and no data is displayed. This behavior may occur if an external trigger has not been received or if the specified timeout is not enough for the acquisition to complete. The default value allows NI-DMM to calculate the timeout automatically. The default value is default –1 s.
  • Sample interval (s)—Sets the amount of time in seconds the DMM waits between measurements. Specify a sample interval to add settling time between measurements or to decrease the measurement rate. Sample interval (s) only applies when acquiring multiple samples and when no switch modules are added to the Switch devices list or in the synchronous scanning of switch modules; in both of these cases, the sample trigger is set to Interval. When Sample interval (s) is set to 0, the DMM does not settle between measurements. When no switch modules are used, the default value is -1 and it ensures that the DMM settles for a recommended time. To configure the Sample interval when in the synchronous scanning of switch modules, use the Advanced Configuration dialog, available from the Switching tab page. The default Sample interval in that case will depend on your switch module settling time.
  • Auto sample interval (s)—Specifies if Sample interval (s) is automatically selected by NI-DMM.
    • True (default)—Allows NI-DMM to choose the Sample interval (s) value.
    • False—Sets the Sample interval to the present value.
Switching Contains the following options:
  • Add device—Displays the Add Switch Device(s) dialog box, where you can select the additional switch module(s).
  • Remove device—Removes the switch module you select from the Switch devices list.
  • Switch devices—Contains the resource name of the switch module.
  • Topologies—Lists the possible topologies for the associated switch module.
  • Add channel—Displays the Add Switch Channel(s) dialog box, where you can select the additional channel(s) from which to acquire data on the switch module.
  • Remove channel—Removes the channel(s) you select from the Scan list.
  • Scan list—Specifies the scan list to use. NI-DAQmx uses this value to set the Scan List attribute.
  • Up—Moves up the channel(s) you select from Scan list.
  • Down—Moves down the channel(s) you select from Scan list.
  • All channels—Selects or deselects all channels in the Scan list.
  • Advanced—Displays the Advanced Configuration dialog box, where you can configure additional parameters.

Block Diagram Inputs

ParameterDescription
closeUsed for optimization in a loop. If TRUE, closes all references and reinitializes the device the next time called. If FALSE, uses the current device handle on the next call. The default is appended to the control name.
error inDescribes error conditions that occur before this VI or function runs. If an error occurred before this VI runs, the VI passes the error in value to error out. This VI runs normally only if no error occurs before this VI runs. If an error occurs while this VI runs, it continues and sets its own error status in error out. Use error in and error out to check errors and to specify execution order by wiring error out from one node to error in of the next node.
max time (s)Specifies the timeout value for the Express VI configured for multipoint or continuous acquisition.

Block Diagram Outputs

ParameterDescription
signal outReturns the data collected by the DMM.
signal out of range?Returns whether the measurement value is within the configured range.
error outContains error information. If error in indicates that an error occurred before this VI ran, error out contains the same error information. Otherwise, it describes the error status that this VI produces. Right-click the error out indicator on the front panel and select Explain Error from the shortcut menu for more information about the error.

Examples

LabVIEW users can use the LabVIEW Example Finder to search or browse examples. NI-DMM examples are classified by keyword, so you can search for a particular device or measurement function.

To browse the NI-DMM examples available in LabVIEW, launch LabVIEW, click Find Examples, and navigate to Hardware Input and Output»Modular Instruments»NI-DMM (Digital Multimeters).

You can find the installed locations of example programs in the NI-DMM Readme File.

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