Using the Voltmeter

Introduction

This guide explains the use of the Voltmeter instrument in WaveForms. This instrument is used to probe AC and DC voltage signals.


Prerequisites

  • A Digilent Test & Measurement Device with Analog Inputs
  • A Computer with WaveForms Software Installed

1. Opening the Voltmeter

1.1

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 the Select button (2) 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 (3.), or by selecting “Device Manager” from the “Settings” menu at the top of the screen.


1.2

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.


1.3

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

To demonstrate the capabilities of the Voltmeter instrument, the Supplies instrument will be used to provide a voltage to measure. Section 2.2 of this guide describes setting up a simple loopback circuit between the Voltmeter and Supply pins.

Connect the Test & Measurement Device's positive programmable supply output pin (red wire, labeled “V+”) to the device's analog input Channel 1 pin (orange wire, “1+”).

Connect the Test & Measurement Device's negative programmable supply output pin (white wire, “V-”) to the device's analog input Channel 2 pin (blue wire, “2+”).

If the Test & Measurement Device has differential analog input channels, 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 device's ground (black wire, marked with a down arrow).


2.2 Software Setup

Return to WaveForms' Welcome page by clicking its tab at the top of the screen. In the Welcome page, open the Supplies instrument and click the “Master Enable” button to turn on the power supplies.

In order to show both the Voltmeter and the Supplies instruments on the screen at once, click on the Docking Windows button () in the top right corner of the screen.

Note: To return to the default tabbed view later, click on the Tabbed Windows button () adjacent to the Docking Windows button.


2.3 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 the voltage readings.

In the Supplies instrument, change the output of the positive supply to 2.5V and the negative supply to -3.2V. Observe the new values in the Voltmeter screen.


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.

Next Steps

For more guides on how to use the Digilent Test & Measurement Device, return to the device's Resource Center, linked from Instrumentation 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 Scopes and Instruments section of the Digilent Forums.