Using the Voltmeter
Voltmeters are used to take quick and easy measurements of AC and DC analog signals. This guide explains the use of the Voltmeter instrument in WaveForms.
- A Digilent Test & Measurement Device with Analog Input Channels:
- A Computer with WaveForms Software Installed
1. Opening the Voltmeter
Plug in the Test & Measurement Device, then start WaveForms and make sure the device is connected.
If no device is connected to the host computer when WaveForms launches, the Device Manager will be launched. Make sure that the device is plugged in and turned on, at which point it will appear in the Device Manager's device list (1). Click on the device in the list to select it, then click on the buffer size (2). Click the Select button (3) to close the Device Manager.
Note: “DEMO” devices are also listed, which allow the user to use WaveForms and create projects without a physical device.
Note: The Device Manager can be opened by clicking on the “Connected Device” button in the bottom right corner of the screen (4.), or by selecting “Device Manager” from the “Settings” menu at the top of the screen.
Once the Welcome page loads, in the instrument panel at the left side of the window, click on the Voltmeter button to open the Voltmeter instrument.
Once the Voltmeter instrument opens, the window contains a table of the available channels (columns) & the results of several calculations (rows).
2. Using the Voltmeter
This section walks through setting up the Voltmeter instrument to capture voltage measurements.
2.1 Hardware Setup
The Voltmeter instrument takes readings from a circuit connected to the analog input channels. Its functionality can be easily demonstrated even without a circuit to test by using either the Waveform Generator instrument or Power Supplies to generate a signal.
If using the analog output channels, open the Wavegen instrument, and run it with default settings (note that a 1 V sine wave corresponds to an RMS Voltage of 700 mV). If using a power supply, open the Supplies instrument and enable it.
Note: Negative pins and grounds should be connected as required by your device. If using an Analog Discovery 3, Analog Discovery Studio or Analog Discovery 2, make sure to connect the analog input channel negative pins, labeled “1-” (orange wire with white stripes) and “2-” (blue wire with white stripes) to the ground of the connected circuit. If using an Analog Discovery Pro (ADP3450/ADP3250), connect the BNC cable ground clips to the ground of the circuit you are measuring.
The analog input channels can be used with BNC Cables if supported by your device. For more information, see the Using the Oscilloscope guide. If 10x attenuation is used with the cables, this value must be entered into the appropriate channel's attenuation field, found in the gear () dropdown, next to the Voltmeter's Start/Stop button.
2.2 Run the Voltmeter
In the Voltmeter instrument, click the Run button () near the top of the window to begin measuring the signal voltage. The cells in the table will update with voltage readings automatically.
Note: Using Multiple Instruments
The Voltmeter instrument can be used with other WaveForms instruments. Using multiple instruments at the same time is helpful in a wide variety of situations. One example would be to use the Waveform Generator to stimulate a circuit under test, the Power Supplies to provide power to the circuit, and view the response with the Voltmeter, all at the same time. More information on how instruments can be operated together can be found in the Using Cross Triggering guide.
It should be noted that the analog input channels cannot be shared by multiple instruments. When the Voltmeter is enabled, any other instruments using the analog input channels are disabled. Other instruments that use the analog input channels include the Oscilloscope, Data Logger, Spectrum Analyzer, Network Analyzer, and Impedance Analyzer.
3. Voltmeter User Interface Overview
The Voltmeter shows measurements for the DC component of the signal, True RMS, and AC RMS.
The Voltmeter can be configured by clicking the Gear icon () to the right of the Run button. This menu can be used to change the update frequency, offset, range, and attenuation as well as enable/disable channels.
The File menu, in the menu bar at the top of the Voltmeter instrument, allows the user to save and load Voltmeter instrument configurations and export an image of the Voltmeter.
The Control menu exposes the same functionality as the Single, Run and Stop buttons, and lists hotkeys for the buttons.
The Window menu provides a fast way to switch to other tabs open in WaveForms.
For more guides on how to use the Digilent Test & Measurement Device, return to the device's Resource Center, linked from the Test and Measurement page of this wiki.
If voltage values seen in the Voltmeter are significantly different from expected, please calibrate the device by following the Calibration Guide.
For more information on WaveForms visit the WaveForms Reference Manual.
For technical support, please visit the Test and Measurement section of the Digilent Forums.