Concentrated oxygen

David Boyd is a senior test engineer at Respironics (www.respironics.com) in Kennesaw, GA, a company that manufactures medical equipment including oxygen concentrators. A 10-year Respironics veteran, Boyd works with electrical and mechanical engineers to ensure that the company’s products are designed to accommodate test. He also works with manufacturing to support auto-mated test and data analysis. Martin Rowe recently interviewed Boyd by telephone.

Q: What is an oxygen concentrator?

A: An oxygen concentrator removes nitrogen from air and produces an output that is typically 93% to 95% oxygen. Physicians prescribe oxygen concentrators for patients who need more oxygen than the air can provide. The units weigh about 30 lbs and are used in many homes.

Q: Describe a typical test.

A: Each of our test stations consists of a two-bay rack. One bay contains valves, tubing, and mass-flow controllers that control the test-flow rate of oxygen from the concentrators. The stations also route each unit’s output to a pressure sensor, and they multiplex each unit’s output to an oxygen analyzer. We use a data-acquisition card to monitor the pressure transducers’ 4–20-mA outputs and to control the valves. The stations also communicate serially with the concentrators.

Q: How do you support manufacturing?

A: I developed automated test stations for our latest line of concentrators. I specify the test equipment and write the software. I also visit production every day to get ideas for how to improve the tests or make them easier for the operators. I keep the test data in databases and use the data to monitor our production process.

Q: What have you done to improve test for the operators?

A: The test area is large, and concentrators may be some distance from the test station’s monitor. I made it easier for the operators to control the test station by giving them a wireless interface. An operator uses a Bluetooth bar-code scanner to scan the unit’s ID and test position, which tells the station that the unit has been added to or removed from the floor. The station responds with text-to-speech outputs to the test operator through a radio transmitter and also alerts the operator when units complete test.

I also installed a temperature/humidity monitor on the factory floor that is connected to the test stations over a LAN. The stations poll the monitor once a minute. By using a network, we need only one monitor, and all test stations work from the same data.

Q: What do you do with the test data?

A: I store test results in a SQL Server database. We add several thousand data points a day because we produce in high volumes and take multiple oxygen purity, pressure, and other measurements from each concentrator. Our QA engineers use the data to track our manufacturing process, looking for signs that the oxygen-purity measurements are drifting.

Q: How do you work with design engineers?

A: I work with electrical and mechanical engineers by suggesting features that ease testing. For example, I asked for a serial diagnostic port so that the automated testers can monitor concentrators during a test. We also use the ports to download firmware updates and operating parameters to the units and to calibrate them.

Q: Must Respironics’ products comply with specifications from regulatory agencies?

A: Yes. We document our test stations, validate them against a protocol that demonstrates they reject out-of-spec units, and verify calibration regularly, in compliance with FDA and ISO agencies.