Optimize Multi-DUT Test Plans with PTEM DUT Variables
Developing a test plan that handles multiple devices under test (DUT) can be challenging. You must manage the instrument setups and measurements for each of the DUT to ensure that your test plan assigns the test results correctly.
A common approach to creating such a test plan is to code everything sequentially. You start with the first DUT, create all the test and result verification steps, and finish it off by assigning the results to that DUT. This completes the test sequences for the first DUT in your project. For the subsequent DUTs, you duplicate the entire test sequences from DUT1 and just update the DUT number for the required test steps, like result assignments. While manageable for a small number of test steps, this method becomes inefficient and error prone as the number of test steps increases. It leads to bloated test plans, slower load times, and increased debugging complexity.
Using PathWave test executive for manufacturing (PTEM), you can avoid such inefficiencies. In PTEM, you can choose to work with your DUT individually or manage them dynamically as a variable entity. PTEM offers a DUT variable data type that you can use to stand for a DUT in your test plan. This allows you to switch through the list of DUT numbers within the same test step during the test execution without the need to duplicate the same test step for each DUT number. The result is a test plan that is less complex and more efficient than the conventional method of managing DUT individually.
Just like how you will create a regular variable for your testplan, you create your DUT variable with the data type set as DUT. When assigning a value to the DUT variable, PTEM automatically displays a list of the available DUT numbers in your testplan for selection. You can only assign DUT numbers to this variable and not any other values.
Figure 1: DUT type variable allows user to set its value from a drop-down list of all available DUT
In Figure1, we have the SelectedDUT variable setup with the DUT data type. The drop-down selection lists all the DUTs that are set up in the testplan, which is UUT001 to UUT003. In other words, SelectedDUT can only hold one of these 3 values at any given time. This gives you the ability to switch between DUT numbers in the same test steps easily. During the testplan execution, you can use a regular variable assignment step to set the value of SelectedDUT, or you can use it in a loop to sweep through the DUT list.
Using variable assignment steps, you can select the DUT number that you need and assign it to SelectedDUT. Subsequent test steps referencing SelectedDUT will run on the assigned DUT automatically. This is especially useful when DUT selection depends on prior measurement results.
Figure 2: Using the Assign Variable step to set a value to SelectedDUT variable.
A typical use case is a multi-site test fixture where the operator randomly loads the DUT onto any of the test sites. The testplan in Figure2 shows the usage of Assign Variable test step to set the value to the SelectedDUT variable. Read Site Status queries the test system for the status of the test sites. Receiving a response triggers the following IF-Else steps to set the SelectedDUT value. So once the operator loads a particular test site, testplan can set the DUT variable, and the subsequent test steps will apply to that selected DUT number. With the DUT number set, the test plan can select specific instruments, like the barcode readers covering the individual test sites. The rest of the test steps simply execute according to the DUT number represented by SelectedDUT variable.
Therefore, by using the DUT variable type in PTEM, the DUT numbering in the test steps becomes dynamic without you having to hard code each step with their respective DUT number, making the test steps generic. So, there is no need to duplicate the same set of test steps multiple times just to hard code each set to a specific DUT number. In this way, we can keep the test plan short and easy to manage.
In summary, DUT type variables in PTEM allow you dynamic control of the target DUT during runtime. In a multi-DUT test plan, this cuts redundant test sequences just to hardcode the DUT assignments. Without those unnecessary steps, test plans can be more compact, easier to maintain, and debug.
PTEM also supports instrument variables that allow you dynamic control over instrument assignments. For more information, check out the Instrument Variable demo video on Keysight Hands-On Youtube channel.
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