Hardware Testing Process – How to test products during production

A typical hardware testing process

  1. Create a testing environment (e.g., measurement hardware, test software, cabling, fixtures, etc.)
  2. Place part into the condition needed for the measurement (apply pressure, voltage, temperature, etc.)
  3. Take some measurements
  4. Put those measurements through one or more pass/fail criteria
  5. Record the results as either summary data or verbose raw plus summary data
  6. Repeat 2-5 as needed to sweep through input conditions
  7. Create a final report document
  8. Declare the part as good or bad
  9. Repeat 2-8 for as many parts as need to be tested

That outline is an extremely brief version of a big topic. We’re going to try to add some clarity, but note that it’s not possible to cover the detailed nuances of any particular product or sub-assembly while trying to cover the broad range of hardware out there (if you work for a US-based company developing industrial products, feel free to reach out for a chat).

Manufacturing test vs design validation

In this article, we’re focused on manufacturing test. This testing occurs during production before the part leaves the factory or is rolled-up into an assembly. Also known as end-of-line test or final test. There’s another aspect of test not being discussed: design validation. The goal with design validation is understanding and analyzing the design limits of the product to better understand how it’s likely to perform in the real world, and provide feedback on any areas of potential design optimization before the final revision of the design gets produced.

Certification testing

There’re also various forms of certification testing (e.g., CE, FCC, UL, etc.). This testing is generally performed by certified labs dedicated to this type of testing.

How to determine what needs to be tested

Deciding what’s important to test in production is usually driven by one of two ways:

  1. Intimate domain knowledge of the product being tested
  2. Required industry standards

You’ll obviously want to test any functionality related to safety or mission-critical functionality. Beyond that though, a lot of determining what to test has a lot to do with performance and accuracy. Which aspects of your product are most likely to fail based on variations in the production process?

Some common components/sub-assemblies to test include:

For electronic parts:

  • power supply voltages and currents,
  • signal levels and frequencies at various test points,
  • range of operation to check linearity and accuracy,
  • and so on.

For mechanical parts:

  • dimensional tolerances,
  • range of motion (i.e., speed, distance),
  • forces,
  • temperatures,
  • power draw and output for efficiency measurements,
  • flow rates,
  • and on and on, because there are so many types of mechanical parts.

For optical parts:

  • mechanical tolerances,
  • power input and output,
  • transmission and reflection properties as a function of wavelength,
  • and so on.

For communications parts:

  • bandwidths,
  • transmission power,
  • receive power,
  • bit-error-rates,
  • distortion,
  • and so on.

And the list goes on because humans make a lot of different things.

How to test your product

At a high level, you need to figure out what makes sense to automate and what makes sense to have a human manually test. And, note that a test can be a combination of automated and manual, not just only automated or only manual.

Things that lend themselves well to automation are generally those that satisfy the following 3 criteria:

  1. don’t require complex external connections or mounting to make the product run (e.g., several multi-pin connectors and harnesses, hydraulic fittings, mounting in jigs and frames),
  2. can be described in a simple algorithm so a computer can be programmed to execute the steps,
  3. and very repetitive tasks that would bore a human.

Things that are often better-suited to manual testing are the opposite and, more importantly, should be done whenever the cost of automation is more than the cost of performing manually (don’t forget to include the wasted cost of erroneous testing done by tired humans).

At a more detailed level, you’ll need to figure out what signal conditioning, data acquisition, UI, reporting, and so on, you’ll need to create a test system. See this Custom Test System Buyers Guide for more detail.

Next Steps

Here are some other articles you may be interested in. If you work for a US-based manufacturing company and want to discuss your testing needs, you can reach out here.