Automatic installation testing

The cause of all this activity is not at all supernatural. During the chassis adjustment, a test rig automatically checks the telematics equipment in the vehicle. Depending on the scope of the check, this can include up to ten test sets. The centerpiece of this rig, called the “Communications Testing System” (CTS), is an electronic tower with a display, control computer, antenna combining unit, and base station simulator for the radiotelephony.

The tower is connected with antennas in the upper section of the test rig. All the test signals are emitted into the car via these antennas. Through the diagnostic unit, the IS tester, the tower is also connected to the car via the onboard diagnostic interface. The job of the IS tester is to read out the signals arriving in the vehicle. The computer in the test rack now compares the transmitted signals with the signals arriving in the car and then evaluates, for instance, whether the GSM antenna is working, whether the radio is correctly receiving the VHF transmitter, whether a mobile telecommunications connection can be established to the cell phone, and whether the speakers of the surround sound audio system are working flawlessly.

This fully automatic test system was conceived by engineers from the Quality Analysis unit of Daimler Research in Ulm. Says Johann-Friedrich Luy, head of the CTS project: “CTS measurements are ultra-precise and automatic, requiring no extra testing time. The system is robust and reliable.” Compared to previous tests, the CTS detects even the smallest signal attenuation, which is around 5 dB. Up to now, engineers have had to accept a range of up to 45 dB. And whereas an average of one in a hundred cars used to slip through the inspection with an installation defect, Luy now confidently asserts that CTS enables his team to “find every defect.” And that was the objective for the customer that ordered the system — the Production Planning department at Mercedes-Benz Cars.

Robust and precise