Application Summary
Forklift trucks may be one of the most curious-looking vehicles around the warehouse or on the factory floor, probably because they are designed for utility and hard work, not for appearance. And to make them most useful and reliable, technical specialists spend a lot of up-front design engineering time characterizing how operators treat them.

For example, a major forklift manufacturer records critical data on both production and new prototype forklifts to get a reading on how well the truck’s components stand up to the rigors of every day use. Sometimes, this is done at a customer’s site. Tests are set up to measure braking distance, speed, and acceleration under a specific duty-cycle pattern. The tests also include measuring battery consumption, a range of voltages and currents, thermocouples, hydraulic pressures, and optical rotary encoders. From the data collected, test engineers determine life expectancies for numerous components such as horns, switches, batteries, relays, and accessories, and they recommend design changes where needed.

Potential Solution
During the early 1990s, the forklift manufacturer had purchased a stand-alone logger comprising some extremely robust data acquisition system modules that served well enough over the years. But recently, it was time to upgrade. The company investigated new systems that were available and assessed the cost versus the benefits of upgrading the old system. The company determined that it would cost at least 80% that of a new system to upgrade the one it was using. The company further realized that it would still be faced with the old system’s limitations, such as relatively expensive training. For instance, company personnel would need to attend a two-day, off-site session to learn the new upgrade. Moreover, the old system used proprietary software that was particularly difficult to learn.

IOtech’s Solution
When the forklift manufacturer investigated the new data acquisition systems that were available, it chose an IOtech LogBook/360. Its engineers determined that when compared to the old system, the LogView software that comes with the LogBook is much easier to understand and use. The lab supervisor trained two technicians in just four hours, compared to the two-day training session previously needed.

The company now uses a stand-alone LogBook/360 connected to a DBK82 thermocouple card, a DBK8 8-channel high-voltage card, and a DBK80 16-channel low-voltage card. The digital signals connect directly to the P2 and P3 ports on the LogBook. Various thermocouples interface the DBK82 thermocouple card, including 8 type J and 6 type K. The DBK80, 16-channel differential input card handles all other signals, except the 24V battery that connects to the DBK8 high-voltage card.

The encoders are incremental types. They generate a 1,000-step/revolution signal and output two clock trains, A and B, 90^o out of phase with each other. Both outputs connect to two channels of the LogBook and provide both speed and directional information. For example, currently the technicians are performing brake testing using encoders and a 5th wheel. One encoder on the 5th wheel measures the truck position within 1/16th of an inch. The other encoder connects to the drive motor to measure its speed, and by comparing drive motor speed to ground speed, they can determine when the tires may be slipping.

The engineers find LogBooks easy to configure and set up to accept any kind of input. Thermocouples, low-voltage inputs, and most other sensors in the system are conditioned to provide a 0 to 10V output. In addition, the IOtech equipment has been reliable and rugged. Engineers performed a “steel test” that was conducted in and out of freezers, and the LogBook was strapped down to a forklift truck with no particular suspension, just solid rubber tires. Although the LogBook took quite a beating, the data it recorded through all the tests were more than satisfactory.

Conclusion
A major forklift manufacturer’s test labs use a relatively inexpensive but complete IOtech data acquisition system to log real-time, operational variables on their trucks. The data help engineers verify current designs or determine engineering design changes that will ultimately produce a more robust vehicle. Technicians can measure up to 14 thermocouple channels with a LogBook/360 connected to a DBK82 module, 8 high-voltage channels through a DBK8 module, and 16 channels of ±10 VDC signals with a DBK80 module. Opto-isolators interface with on/off switch signals, optical encoders provide motor and ground speed, clamp-on ammeters provide current inputs, string potentiometers provide fork height signals, and special strain-gage sensors measure hydraulic pressures.

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