Although battery-powered computer based instruments are commonplace, they typically lack powerful processors capable of running sophisticated Windows 2000/XP-level applications. They rarely offer large, high-resolution backlit displays, which are critical to running today’s software and providing a comprehensive user interface. The larger and brighter the displays are, the more power they require — and are usually the biggest power draw in any system. The displays on even the most expensive notebook PCs are unusable in outside environments — even in weak sunlight — simply because the brightness of the backlight is limited severely in order to preserve battery life.
A new technology has enabled the development of full-power computers running Windows XP Professional, which can run indefinitely on hot-swappable lithium-ion batteries. Called Side-Hand, the computers use a proprietary power control subsystem to manage power intake from two hot-swappable batteries and a DC input, providing a constant output at several highly regulated DC levels. The control system also manages the automated battery-level checking and recharging when the system is connected to external DC power. Combined with lightweight, high-yield lithium-ion batteries, this power subsystem allows a high-power computer and peripherals to be operated for anywhere from two to four hours, depending on the workload.
A small door on the base of the system can be opened, and either battery can be replaced without interrupting the operation of the system. The power subsystem instantly shifts the load to the other battery. If desired, the second battery also can be replaced. This “hot swapping” capability means that the system can be operated indefinitely from internal batteries, and never needs to be connected to an external AC or DC power source.
A portable battery charger runs from AC or DC, allowing up to four batteries at a time to be recharged. The charger can be unplugged from AC or DC and put into service as a portable DC power supply for any instrument, including a SideHand computer, increasing its battery run time to 300% (from 2 batteries to 6 batteries). This charger can be used as a portable power source for virtually any DC-powered device such as a low-power data logger.
The computers are based on a core platform comprised of a built-in 15" high-resolution display that is visible both indoors and outdoors; a portable, rugged, all-metal chassis; a Pentium 4® computer with two PCI slots; internal 60-Gb hard-disk drive; and flash memory port.
Two hot-swappable, lightweight, high output Li-Ion batteries can be changed while the system is running for continuous operation without connection to external power. A built-in DC power jack also will power the system and recharge the batteries automatically. Wide-range DC input allows the system to be powered from 12V DC automotive power, and the internal batteries act as a multihour uninterruptible power system to keep the computer running during power gaps ranging from a few milliseconds to hours at a time.
The systems can be used as pure computers for field applications, as general-purpose data acquisition systems, or as three-phase power quality (PQ) analyzers. The general-purpose models incorporate a signal conditioning front-end, and data acquisition and analysis software for data recording. The system features from 16 to 64 dynamic input channels. The acquisition software allows up to four video cameras to be connected to the system, so that video can be acquired synchronously with the analog and digital recorded data (Figure 1). In addition, Global Positioning System (GPS) sensors can be attached to provide both a universal time reference in the recorded data, and absolute position information in longitude and latitude, speed, heading, and elevation.
The CAN (Controller Area Network) bus is a standard serial interface built into virtually all cars and trucks built today. But CAN has grown in recent years to include aircraft engines, farm machinery, and even major appliances. In addition, many of today’s sensors have a CAN-bus output. The acquisition software is compatible with CAN-bus interface cards, allowing the system to simultaneously display and record dozens or hundreds of parameters synchronously with the analog inputs. Up to four separate CAN-bus networks can be connected to the system. As a three-phase PQ analyzer, the 16 dynamic inputs mentioned above are replaced with four 70~600 VAC high voltage inputs (rated to CAT III), and four additional current inputs.
The GPS interface is often important in power applications because of the need to time-sync transients and power events recorded by numerous instruments scattered over a wide geography — sometimes even spanning an entire country. Unlike the fixed sample-rate recording normally performed by data acquisition systems, PQ analysis requires that the sample rate be adjusted continuously in order to provide a finite number of samples per phase of the AC sinus. This allows PQ parameters such as RMS, active power, reactive power, phase angle, apparent power, and power factor — as well as meaningful harmonic analysis — to be calculated and displayed in real time, and recorded to disk. In addition, infrared cameras can be attached for simultaneous display and recording of temperature without the need to connect sensors.
Applications are wide and varied for products of this type, including automotive R&D, which requires a range of dynamic and static tests, both in test chambers and on the road. In aerospace applications, the systems can be used for engine testing, which often is performed on remote runways and at locations where easy access to AC power is not available.