Problem
Our customer was having problems caused by rough handling on an ink cartridge production line that caused some cartridges to fail reliability tests. They needed a way to measure shock and vibration during the production line process. They wanted a self contained battery operated acceleration and shock recording instrument that could travel on the production line. The instrument had to fit within the plastic shell of a normal ink cartridge, weigh the same as a normal cartridge, and have the same center of gravity. A means to program the instrument was needed as well as a way to retrieve the data.
Solution
AO designed the hardware and software for a three-axis accelerometer and data recorder that fit in the approximately two cubic inches inside an ink cartridge. It collected 16-bit data at about 100,000 samples per second. It was fairly power hungry because of the high data sampling rate, necessitating a fairly large rechargeable battery. The 3-axis acceleration sensor volume was one cubic centimeter. The circuit boards had to squeeze in around these bulky components. The circuit was too large to fit on a single circuit board, so we produced two four-layer circuit boards, one for the digital circuitry and the other for the analog sampling circuits. The battery was sandwiched between the boards, providing good isolation between the electrically noisy processor and the sensitive analog inputs.
This instrument was equipped to trigger recording in response to an acceleration exceeding a threshold level or record on timed intervals. It could be programmed to start recording in response to stimulation by a bright flash of light upon a photosensor, such as produced by a photoflash unit. This allowed the unit to ride along on the production conveyor belt and then be triggered as it approached a test location. We obtained a calibrated vibration standard to calibrate the instruments.
AO produced a communications interface to connect the Accelerometer to a PC through either a serial or parallel port. This unit also included a battery charger and charge state indicator for the battery inside the instrument. We provided software to run on the PC to program the instrument and collect data.
Results
We delivered several of the instruments to the customer. They worked as expected and allowed the manufacturer to locate and fix the places in the production line that were causing the problems.