Vehicle Data Acquisition For Component Reliability Testing

dataTaker DT80 Intelligent Universal Input Data Logger

A large manufacturer of OEM automotive components needed to conduct an ambitious field test to evaluate the reliability of its latest device. This test involved data collection from multiple vehicles at various locations across the US to study the effects of various environmental conditions on the component. The test needed to run for up to 3 years to capture enough data for accurate statistical evaluation and lifetime predictions, requiring more than 20  measurements including temperature, voltage, speed, run time, and other operating conditions.  Engineers began searching for an intelligent data logging solution with the versatility to accommodate all these different types of signal inputs. Soon 3 other key concerns were identified: first, overall power consumption was very important–the logger only needed to collect data while the vehicle was running, but it had to be continuously powered so that it could quickly respond to the startup and be able to send the data at specific times. Therefore, the power consumption needed to be very low to eliminate the possibility of discharging the vehicle battery if it was parked for a long time period. Secondly, since the vehicles were dispersed throughout remote locations across the country, manual data retrieval was impractical, so the manufacturer wanted to implement a periodic automated data upload via a cellular connection. Finally, the data logging system needed to be as unobtrusive as possible, since these test vehicles were currently being driven by end users.

After extensive evaluation recording multimeters and data loggers with several different types of equipment including hardened PLCs, the customer installed 15 dataTaker DT80 Intelligent Universal  Input Data Loggers for the test project. These intelligent low-power devices featured 18-bit resolution and a ±30 V input measurement range, utilizing a Dual Channel concept allowing up to 10 isolated or 15  common referenced analog inputs to be used in many combinations. Offering 5 to 15 universal analog sensor inputs and 12 digital channels, the stand-alone loggers performed real-time data acquisition inside the vehicles. Each DT80 datalogger featured a built-in display and removable screw terminals for secure connections. High-speed counter inputs, phase encoder inputs and a programmable serial sensor channel enabled the DT80s to easily connect to most sensors and data measurement sources. Temperature, voltage, current, 4-20mA loops, resistance, bridges, strain gauges, frequency, digital, serial and calculated measurements could all be scaled, logged and returned in engineering units or within statistical reporting. Users could also group sampling, logging, alarm and control tasks within schedules to suit their requirements.

To power, the data loggers, a connection from the battery was run to the main power input of the logger while a separate wire was run from the ignition to one of the digital inputs and the WK input of the data logger. The wire from the ignition was only energized when the key was on. Then, utilizing the ability to have multiple schedules within the data loggers and the capability of starting and stopping schedules under program control, a simple schedule triggered by the key turning on or off was created, and in turn, this schedule controlled the main data collection schedules within the loggers. Using the power mode parameter in conjunction with the sleep delay parameter, the loggers were set to go to sleep whenever they were inactive to reduce power consumption to a minimum.

To simplify data retrieval, the dataloggers were paired with an Airlink Raven XE CDMA cellular modem featuring an Ethernet interface that could be connected directly to the Ethernet port of the data loggers.  Power for the modem was sent through the internal Relay channel of the DT80s, allowing the modem to be powered only during the data upload. A timed schedule was created to trigger the data upload at a  specific time each day. Since multiple data loggers were used in the project, the upload times were staggered so that the loggers wouldn’t try to send their data to the server at the same time. Once activated, the upload schedule would close the relay to power up the modem, wait for the modem to register, then establish its connection to the cellular network, send the data via the DT80s’ built-in FTP  server using the copy data (COPYD) command, and then power down the modem when done. All of the data was easily segregated by assigning each data logger a specific directory on the FTP host computer.  A key feature of the COPYD command was the Start option which maintained an internal pointer to the beginning of any new data which hadn’t yet been successfully unloaded. This allowed the intelligent dataloggers to automatically handle situations where the modem wasn’t able to make a connection to the cell network because of poor coverage or when the upload couldn’t complete successfully for some reason. Data transfer via the loggers’ flexible communications arrays included Ethernet, RS-232  communication with PC, SDI-12 and Modbus sensor support, and a USB memory slot. Operators could also archive data on alarm event, copy to USB memory or transfer via FTP. All these options greatly simplified data management.

The DT80 dataloggers’ small size was another important part of the project. The manufacturer was able to conveniently package the DT80 and cell modem in a fiberglass NEMA-rated enclosure that was approximately 1 ft 3. This enclosure was easily mounted in each car’s trunk, creating minimal impact for the vehicle owner and reducing the possibility of tampering. A remote cellular antenna was mounted close by on the underside of the rear shelf below the back window for good signal reception.

The component manufacturer realized several key benefits from installing the dataTaker DT80 in its extensive component test program. The DT80 intelligent datalogger had the flexibility to measure all the physical values required by the demanding tests. These devices also featured the low power consumption, simplified data retrieval (enabled with a connection to the modem), and the small size that were all essential for this application. Users found it easy to work with the included dEX software for trouble-free logger configuration, and the DT80’s many communications options offered convenient data transfer locally via USB or online through FTP.

About 18 months into the test program, the reliability of the data loggers has been very good. Most of the loggers uploaded data every night, and although some may have missed a day or 2 because of poor cellular coverage in their location, they recovered and uploaded any missing data once they got back to a better location.  The quality of the measured data met or exceeded all of the customer’s expectations.  In fact, the one hardware failure that occurred was attributed to the data logger being submerged as a  result of a collision!