Technical Insights

Fixture Identification made simple with RFID

2020-06-25  |  7 min read 

How are you tagging your production test fixtures today? Still using those barcode labels that constantly peels off by itself or getting defaced?

Hard-wired identification code inside a Test Fixture

Or you still using old rigid method of wiring the fixture ID codes directly inside the fixture?

Identification and tracking are critical in the manufacturing process for an automotive product. The data collected and analyzed enhanced the quality of the product and enable tracing of the production history to support investigation works during a product malfunction event in the future. This is especially true for mission critical automotive parts like the electronic control unit (ECU), advance driver assistance system (ADAS), anti-lock braking systems (ABS) and supplemental restraint system (SRS).

Advance driver assistance system (ADAS) need flawless electronics parts for its mission-critical applications

Any failure of parts in these systems is catastrophic and results in loss of life with a million-dollar lawsuit thereafter. Being able to trace back into the production history of the defective part provide investigators with critical information to uncover the truth.

Fixture ID comes in many forms ranging from a simple barcode label on the fixture to hard-wired codes inside the fixture which the test system can access for validation. The use of barcode labels and fixed or handheld scanners are simple and economical, but it does not offer the best efficiency and reliability. The manual operation depends on the integrity of the operators to scan the correct labels Automated and non-human dependent fixture identification in a test system takes away any ambiguity from mistakes arising from human error.

Hard-wired codes provide fully automated identification, are reliable and robust, and are least prone to damages. However, it is not the most economical method as it requires dedicated hardware built into the test system to read the codes. The fixture also needs to reserve part of its valuable tester-fixture interface layout to cater for the additional hard-wired codes access.

Ever thought of using radio-frequency identification (RFID)? That’s what we use on the Keysight FlexiCore Handler system! Using RFID is by far one of the best options in terms of reliability and economic sense.

RFID is not a new technology. There is a wide range of readers readily available in the market today to choose from. Implementation does not require any dedicated hardware built into the test system. All it takes is to connect the reader to the tester and tag the fixture!

RFID tags are programmable, robust and secured. There is no worry of labels peeling off or user scanning the wrong labels. It is easily accessible by the administrator or engineer to reprogram the code without any need of rewiring the test fixtures.

Test fixture and reader are both within the confines of the test. You don’t need an expensive powerful long-range reader to be able to read the tag. Neither do you need a multichannel super-fast reader to read high number of tags at the same time.

Metal and water bodies affects RFID waves. These materials absorb, reflect or refract radio waves making the detection challenging. Between the reader and the tags there is no requirement to maintain line of sight but installing them inside the test system is different. Surface within the metal chassis and parts of the test system reflects or block the radio waves emitted by the reader. These reflections may cause problems resulting is null zone or interference when you attempt to read more than one tags. Therefore, maintaining line of sight between the reader and the tag will be helpful to minimize any blockage of the radio waves. Mounting the reader closer to the tags will help to deliver higher power to the tags and mitigate the effects of reflected waves which are generally lower in strength.

Reader’s antenna has a detection cone which defines the zone where the reader will be most effective in detecting the tags. Facing the antenna in the right direction helps to ensure direct transmission of the radio waves to the tags. Reader cannot be placed too close to the test fixture to cover the whole test fixture under this zone.

Optimum distance between antenna and tags

However, there is very limited space in the test system to allow for optimum distance and it is not possible to cover the entire fixture into the detection zone. Strategically placing the tags on the area covered under the detection zone eliminates this restriction.

Tags placement within detection zone

Implementing RFID for test fixture identification is not too difficult. You just need to know where to place your reader and tags.

I will discuss more about the RFID tags that we use in my next post. Stay Tuned.

As always, feel free to drop me an email (kwan-wee_lee@keysight.com) with your comments or questions. Stay safe and stay healthy!