Technical Insights > Benchtop

Advanced Switch Matrix to Streamline Tests

2019-09-05  |  8 min read 

Test instruments tend to have limited measurement inputs and can measure one or two devices at a time. High volume manufacturing companies test their products by the hundreds or thousands of units per hour (UPH). How then can test equipment managers or test engineers meet the order fulfillment demands? There are a few potential options available. See Figure 1.

Instrument options
Figure 1. Instrument setup options

Option 1 (Add racks of instruments)

Test equipment manager will normally want to optimize test equipment assets. Adding assets to meet UPH or throughput requirements is a straightforward exercise. However, this can be a costly way of managing your test needs, especially when large quantities of instruments must be purchased. The total cost of ownership and return of investment can be a major barrier for you to implement with this option.

Option 2 (Use modular instruments)

Many high-volume manufacturing lines resort to using modular instruments because each instrument card does exactly the specific test function required of a box instrument but with significant space savings. Manufacturing lines are very sensitive to space and cost of testing per unit. The modular systems are, however, less flexible in terms of setup and configuration. Sometimes, you need special modular cards for certain measurements such as temperature and may require special external signal conditioning modules.

Option 3 (DAQ switch system instruments)

Products have now become very complex, with multiple inputs and output channels. Many product designers and even test engineers resort to data acquisition (DAQ) systems to streamline the testing process. Streamlining test means to simplify or make the test process less complex and also to reduce the test instruments required for the job.

What can DAQ switch system instrument do to streamline tests?

Figure 2 shows an example of a DAQ switching system which consists of a mainframe and switching/data acquisition modules.

DAQ970A mainframe and modules
Figure 2. DAQ mainframe (left) and switching/data acquisition modules (right)

One of the most powerful features in a DAQ system is the switching control system. Using the switching control system, you can simplify your test setup, reduce the number of test instruments, and perform multiple devices under test (DUT) testing.

DAQ switching test setup
Figure 3. DAQ with switching module to control batch device testing

Figure 3 is a good example of using a DAQ switching matrix module to streamline your testing. The switch matrix module is fitted into the mainframe. For example, if a module consists of 4 rows by 8 columns (4X8) of switch matrices, some DAQs can concatenate the rows or the columns. You will then be able to make matrices such as 8X8, 4X16, and so on, limited by the number of module slots of the DAQ mainframe.

In this test setup example, three instruments are connected in three columns via the 2-wire connectors. There are four DUTs connected in four rows via the 2-wire connectors. The precision meter is used to measure voltage or current from the DUTs, the DC power supply is used to DC bias the DUTs, and the electronic load is used to simulate resistive load for testing on the output of the DUTs.

The benefits of using the DAQ switching matrix module are:

  1. Test asset optimization – where a set of test instruments are used to test multiple DUTs. The switch matrix helps to test a batch of DUTs at one go versus one DUT at a time. This switch matrix setup helps save cost and space in terms of the number of instruments.
  2. Simplify your test setup – having this matrix configuration helps you to scale up or down your test process easily. Wiring is also less messy, and setup configurations can easily be done on the DAQ mainframe or remotely via a PC software application.
  3. Test time optimization – when you require to test many different combinations of loads and DC power biasing to obtain a comprehensive test. Switching modules can switch up to 250 channels per second when using the mechanical armature switch module or up to 450 channels per second when using the solid-state switch module. The switching and measuring processes can be done automatically; hence, it helps save total test time for every DUT.

Are there other types of switching modules to streamline tests?

Besides the dedicated switching matrix module, there are other types of switching modules to streamline your tests. For example, the multiplexer switch module, as shown in Figure 4.

DAQM900A solid-state switching module
Figure 4. A switching multiplexer module

This particular multiplexer switch module has 20 input channels. Each channel can measure various types of measurements, such as voltage, current, resistance, capacitance, and temperature. When this module is plugged into the DAQ mainframe, it connects to the mainframe’s internal digital multimeter (DMM). The DAQ mainframe can be configured to scan say from channel 1 to 20 and make measurements from each channel. Hence, if you want to monitor 20 temperature points of a particular DUT, you do not have to buy 20 temperature data loggers.

Another example is the dual four-channel RF multiplexer, as shown in Figure 5.

DAQM905A dual four channel RF module
Figure 5. Dual four-channel RF multiplexer 50 Ω

This switching multiplexer can route test signals between your DUT and your signal generator, oscilloscope, spectrum analyzer, or other instrumentation. It is arranged as two independent 1x4 multiplexers, each with a common shield and a switched center conductor. Multiple banks can be cascaded together for applications requiring even larger topologies—create a 16:1 multiplexer in a single frame.

Summary

Advanced switching using a DAQ system helps to streamline your test processes. For manufacturing test, increasing UPH and asset optimization are very important factors. For product designers, simplifying test setups and reducing test time gives them shorter development time cycles.

The switching modules in a DAQ system are scalable depending on product test complexities. To learn more about Keysight’s versatile DAQ switching and data logging system, please visit www.keysight.com/find/daq970A. The Keysight’s DAQ970A comes bundled with the Data Acquisition Control & Analysis PC software. It helps you to easily control measurement channels for your specific test configurations from one or multiple data acquisition systems. It can also Intuitively log and view real-time measurements with a variety of display types to interpret your data faster. For more information on the Data Acquisition Control & Analysis PC software, go to www.keysight.com/find/benchvue.