Customer-focused EMC
An exclusive interview with a test engineer
By Martin Rowe, Senior Technical Editor -- Test & Measurement World, 11/1/2008 2:00:00 AM
Dan Dwyer is a principal systems engineer at Allegro Microsystems in Manchester, NH, where engineers develop and test Hall-effect sensors that are used instead of mechanical switches in high-reliability applications in printers, copiers, and cellphones. Digital Hall-effect sensors are used on automobiles and motorized machines to measure rotational speed and position. Analog Hall-effect sensors sense current flow in wires. Senior technical editor Martin Rowe spoke with Dwyer by phone.
Q: What is the role of a systems engineer?
A: I assist in the development of new products from a customer and applications perspective, making sure that the product meets customer requirements. Systems engineers also provide direct technical support to large, strategically important customers.
Q: What tests do you perform to verify that products are customer ready?
A: Much of my testing involves EMC (electromagnetic compliance). Allegro doesn’t have a compliance-test facility, but we need to quickly and thoroughly assess the EMC performance of our products. I test our sensors for immunity to the kinds of interference that they will encounter in the field, based on customer or market requirements. Some tests follow industry standards, while others are customer specific. We invested in an EMC test facility primarily so we’d have flexibility and complete control over our testing.
Q: Why do you perform customer-specific tests?
A: Customers, especially in the automotive industry, have tests that often vary from published standards. Each of the three major US automakers requires BCI (bulk-current injection) testing on sensors. Though all three refer to the ISO 11452-4 standard, each automaker makes exceptions to at least part of the standard and offers additional requirements.
Q: What EMC immunity tests do you perform?
A: We run radiated and conducted emissions tests. We’ll subject sensors to direct RF fields using a TEM (transverse electromagnetic mode) cell. BCI, though, is the key RF test for the automotive market. The BCI test injects current into a system at frequencies from 100 kHz to 400 MHz. BCI testing is becoming popular for low-frequency product evaluations.
Q: How do you inject current into a sensor?
A: Per ISO 11452-4, I use an indirect method with a current clamp. Placing a clamp around a harness, I inject a signal into the probe that couples into the cable wiring, creating a current. With a current clamp, I can test for both common-mode and differential-mode current.
Q: How do you measure the effects of BCI on a sensor?
A: I monitor the sensor’s output signal with an oscilloscope under PC control. Software controls the oscilloscope and EMC test equipment according to the parameters of the reference standard, the requirements of the DUT (device under test), and the specific customer requirements.
Q: Do you perform other customer-specific tests besides EMC?
A: In Manchester, we conduct extensive product characterization that includes both Allegro-standard and customer-specific testing. At our company headquarters in Worcester, MA, we have an environmental test lab where we perform thermal shock, temperature-humidity cycling, and HTOL (high-temperature operating life) tests. We also have a failure-analysis lab where we analyze development products and customer returns.
No related content found.
- 0 rated items found.
Datasheets.com Electronic Parts & Inventory Search
185 million searchable parts
- Part Number
- Description
- Inventory
- Products
- Manufacturers
View All Webcasts
