Smart sensors simplify diagnostics

Many motors, drives and vision systems already have diagnostics, and other equipment is starting to come along. You might find it’s time to start designing your machines to accommodate them.

By Rich Merritt, Senior Technical Editor

WHEN THE U.S. Army adopts a technology, you know its time has come. In August, the Army announced it is equipping its Stryker Brigade military vehicles with embedded sensors that detect problems, inform the vehicle operators, and transmit data back to central headquarters locations via wireless and satellite. The system also triggers a global positioning system that identifies the position of the vehicle. The vehicle operator, contact repair team and support battalion can decide what to do about the problem, and take appropriate measures.

This procedure sounds almost exactly like what some machine builders are starting to do: Identify problems with embedded sensors in a machine, inform the operator, and provide enough information via the Internet so experts back at the builder’s brigade…er, company headquarters can decide what to do about it.

It makes sense. The Army has the same problems as machine builders and their customers: a lack of trained technicians, extremely complex control devices, and worldwide deployment of machines. The Army’s machines also suffer from the same kind of mechanical and electrical problems as machine builders; that is, problems that could be easily fixed if symptoms are identified early enough for a little preventive maintenance. 

As for complex controls, the situation also is similar. Most industrial machines don’t have a Stryker’s advanced surveillance system with a “horizontal technology initiative” (HTI) thermal imager, day TV and laser rangefinder, but machine builders have plenty of problems dealing with vision and motion control systems, networks, PCs and PLCs. Clearly, sensors, controls and electromechanical systems with built-in diagnostics are the answer for both the Army and machine builders.

Many motors, drives and vision systems already have diagnostics, and other equipment is starting to come along. You might find it’s time to start designing your machines to accommodate them.

Schneider Electric’s MicroLogic circuit breakers, for example, monitors the quality of incoming power, and can tell you why a breaker fired. “You should always ask ‘Do I want to reset this?’ when a breaker blows,” says Alan Kuntz, marketing manager for circuit breakers at Schneider. “If it’s a long-time pickup or a long-time delay, then it may be safe to reset it. However, if it was a short-time pickup or delay, an instantaneous fault, or a GFE trip, you may want to do some investigating first.”

Because the MicroLogic reports on the harmonics, current and power quality--along with dozens of other variables--you’ll have plenty of data to look at. You also might find that fluctuating power quality is causing problems with motors, welders and other devices.

Detecting pending mechanical problems such as bearings going bad requires a vibration monitor. You can put a simplified vibration sensor into your machine for only a few hundred bucks. The Machinery Fault Detector from PCB Piezotronics detects high-frequency impacts related to bearing faults and lube starvation, and provides a 4-20 mA signal proportional to the magnitude of vibration. The 4-20 mA output can be wired directly to the inputs of a PLC, PC or other machine controller.

Texas Instruments has a similar device, the Pump SystemAlert, suitable for pump systems and other motor-driven equipment. It combines vibration monitoring with electrical sensing so a machine builder can channel other inputs into the system, such as process or system parameters, and create a custom alarm monitor tuned to the machine. “A significant percentage of motor-driven equipment failures are detectable through electrical monitoring,” says Jim McGuinness, program manager at TI. “Monitoring electrical characteristics can help find problems such as motor overload, phase imbalance or even improper wiring.” The price is $4995. 

In the dirt-cheap category you’ll find the HOBO motor and state data loggers from Onset Computer. Priced at about $75 each, they provide a simple way to record equipment on/off cycles or state changes, respectively. The data could show how efficiently equipment is running, or help techs find cycling problems. Outputs are to a PC via a USB interface. 

Similar products with built-in diagnostics are coming into the market rapidly. With a little research, you should be able to find enough smart devices to keep your machines monitored remotely back at your own brigade headquarters.