Using Power Supplies with a Readback Plot
This guide explains the use of WaveForms' Power Supplies instrument for devices where it features a readback plot. This instrument is used to configure a Digilent Test & Measurement Device's variable power supplies. The instrument is also referred to as the Supplies in WaveForms. On devices like the Analog Discovery Pro (ADP5250), the Supplies instrument will look like what you see in the guide below.
If you have a different Digilent test and measurement device, take a look at Using the Power Supplies instead.
- A Digilent Test & Measurement Device with variable Power Supplies with readback capabilities:
- A Computer with WaveForms Software Installed
1. Opening the Supplies Instrument
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.
Once the Welcome page loads, in the instrument panel at the left side of the window, click on the Supplies button to open the Power Supplies instrument.
Once the Supplies instrument opens, the window contains the controls for the three variable power supply rails, described in the next section.
2. Using the Supplies
This section walks through setting up the power supplies and voltmeter to measure the DC output of the power supplies.
Important: The power supply leads are not to be used as a scope or DMM input. These measurements are only intended to be used to measure what the power supply is currently outputting. Shorting the supplies out to a scope or DMM connection can result in damage to your device.
2.1 Hardware Setup
- Hardware Setup with Analog Discovery Pro (ADP5250)
The ground and power supply rail screw terminals can be probed with a Digital Multimeter (DMM) by either touching the DMM probes to the metal pads at the end of the supply rail's terminals, or using cables to first break out the power supplies to a breadboard or other circuit. Setting the DMM to measure DC voltage allows you to easily test that the supply rail voltage matches the value specified by WaveForms.
- Hardware Setup with Discovery Power Supply (DPS3340)
Plug in a set of banana plug connectors into the Output 1 port on the front of the Discovery Power Supply. Please connect the red banana plug to the red connector on the Discovery Power Supply and the black banana plug to the black connector. While theoretically you could use any color, keeping things the same will avoid confusion when working with your circuit. Use the alligator clip or minigrabber clips to connect the power supply to your Device Under Test.
2.2 Software Setup
No additional Software Setup is required.
2.3 Enable the Supplies
When the Supplies instrument is first opened, all power supplies are disabled.
The “Master Enable” button can be used to switch all of the variable supplies off or on at once. While the Master Enable is off, each power supply can be set to a Ready or Off state, if the supply is ready, it will be turned on when the Master Enable is set to on.
Make sure that the power supplies are set to Ready, then click on the Master Enable button to turn them on.
3. Power Supplies User Interface Walk Around
The remainder of this guide describes the functionality of the rest of the Power Supplies user interface. While following along, experiment with power supply controls described, and look back at the Voltmeter to see how they the voltage outputted by the variable supplies is affected.
3.1 Readback Plot
The readback plot, including the readback channel names, the plot itself the control buttons above it, and the table of channel names on the left are used to measure the actual voltages and currents of each of the supplies over time. This graph helps you see that the power supplies instrument is outputting what you have set for the device.
3.2 Enable the Supplies
When the Supplies instrument is first opened, all power supplies are disabled. You will see a red X next to the Master Enable description. This means that all supplies are off. Clicking on the word Master Enable will change the red x to a green check mark and turn on the supplies.
3.3 Controlling Individual Supplies
You can turn off and on each of three Supplies by clicking on the individual checkbox and then clicking the Master Enable button. From the pull down menu you can select the voltage and the current limit. If you see a green circle next to the supply, it indicates that the supply is on.
Underneath the Master Enable box there will be an option to enable tracking. If you select this checkbox, the inversely matching supplies will track each other. For example, if you set a +25 V supply to +21 V, the -25 V supply will “track” to the inverse, so in this case -21 V. Similarly, the current limitation will be tracked as well.
3.5 Voltage Drop Down
Each of the three power supplies have a drop down menu associated with both voltage and current. By changing the value, you change the maximum amount the parameter can reach when Master Enable is on.
3.6 Supply Settings (Gear) Menu
The gear dropdown for each supply contains the limit settings for that supply. For instance, if you set the maximum voltage of the a supply to less than it's maximum value, it will be impossible to adjust the power supply beyond that limitation.
For more guides on how to use your Digilent Test & Measurement Device, return to the device's Resource Center, linked from the Test and Measurement page of this wiki. If you want more information on the features and specifications of your device, refer to its Reference Manual and Specifications sheet, respectively, which can be found on its Resource Center.
If voltage values output by the Supplies 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.