BUYER BEWAREAs computers continue to migrate from the office to the factory floor, one has to define the differences between these two environments. Without this definition it is possible to become prey of the marketeers for whom anything that mounts in the 19-inch rackmount is 'industrial' and what stands on the desk is not.
Although you can argue about the definition of what constitutes industrial features, all agree that, just like the office computer, industrial computers must be compatible with popular operating systems such as DOS, Windows 98/NT/2000/XP QNX, Linux, etc.They must also be very reliable and easy to repair. Reliability of the industrial computer has tremendous impact on cost of the ownership, as a failure, in some cases, can cause shutdown of the plant. In many environments, a few hours of shutdown can easily cost in excess of $100,000. This is why many buyers of industrial computers ask how often will they fail rather than how high is the price.
THE IMPORTANCE OF AIR FLOWThe industrial environment is normally characterized by extremes of temperature, contaminants, shock and vibration and large fluctuations of input power, including electrical transients, noise and brownouts. Withstanding a wide range of the ambient operating temperatures can only be assured with adequate, thermostatically controlled heating or cooling of the computer enclosure. Although the lower operating range can be easily extended with low cost heating pads, extending the range above 50° C may require costly air conditioners. Beside the ability to cool the computer down, recirculating air conditioners also stop dust from accumulating in the enclosure.
Dust is by far the biggest killer of computers on the factory floor. Over long periods, dust clogs up fan filters and accumulates over fine components and traces on the circuit cards. In some plants the dust carries contaminants. For example, rubber dust has sulphur content that is fatal to copper. It combines with fine copper traces on the cards and pulverizes them, causing intermittent faults. The recirculating air conditioner is an effective solution to extend the operating temperature range. However few can justify this solution because of the high cost, running from $2000 to $3000.ADAPTIVE AIR FLOW
A good compromise is adaptive air flow, proportional to the temperature inside the computer. Temperature is measured with a sensor connected to a solid state controller, which controls the supply of power to air fans. At low temperature the fans idle at low speed. In the mid range, 25 to 35° C, air flow is proportional to temperature and at 35° C and higher, the fans run at full speed, and an alarm is set at 50° C. This way dust does not build up as fast as if the fans always on at full speed. In other words the computer enclosure responds to heat like human-adaptive system rather than a vacuum cleaner running at full blast.
With adaptive air flow there is no need for air filters, which lowers the cost of maintenance and prevents failures caused by forgetting to clean them.Temperature protection of the industrial PC is an important consideration as, for example, Intel guarantees proper operation of Pentium chips only up to 50° C. CPU coolers mounted to the chips are effective in dispersing heat away from the IC, however good air flow needs to be provided to prevent heat rise problems in the entire volume of the chassis. The chassis itself acts as a heat exchanger and for this reason it is better to leave it unpainted, as zinc plating or anodizing finish is a sufficient protection against corrosion in a typical environment.
ANTI-VIBRATION MOUNTING
Anti-vibration mounting is a must for computers installed in the vicinity of large rotating machinery or anything else that moves. Steady vibration will crack solder joints on the computer back-plane as a result of metal fatigue. This can cause costly and difficult-to-find intermittent faults. Mounting the computer on a shelf is better in this case than using a rackmount. The computer can be easily isolated from the shelf with the anti-vibration mounts selected for the weight of the computer, resonance frequency and damping characteristics over the range of the vibration. Each case is different depending on what is causing the vibration: large electrical turbine, ship engine, helicopter motor or a moving car. Elastomeric anti-vibration mounts provide an effective protection for shelf-mounted industrial computers.
UPS
Electrical considerations related to input power can be easily solved by an external uninterruptible power supply (UPS). It will not only provide emergency power, but it will also act as a voltage regulator and transient suppressor and will have a built-in isolation transformer. It is by far cheaper to use a standard PS/2-type mass-produced power supply with an external UPS than to buy an expensive OEM power supply with superior electrical characteristics. The advantage of the UPS solution is the low cost of the mass-produced product.
But a consumer mass-produced power supply is not recommended for the industrial environment. Its fan's rotor rotates in brass bushings which will probably fail after a year of operation, stopping air flow. Care must be taken to assure that the fan in the power supply has a ball bearing and high air flow (>4OCFM) capacity to provide adequate cooling over many years. Also, the power supply has to be at least 70% efficient and handle a wide range of input voltages to provide some immunity against brownouts. Consumer-grade supplies typically operate over +/- 10% input range, which is not adequate for industrial environments.WHY IPC?
Looking at industrial computer performance, the game is changing. Even Intel now manufactures chipsets specifically for consumer and industrial markets. The consumer chipset is optimized to run video games and it is cheaper than the faster industrial version. On the classical passive backplane CPU (not a motherboard style), the high performance Triton II chipset is becoming popular. Other features to look for include error correction circuitry, built-in temperature monitor and a watchdog timer. An industrial CPU must have bus drivers capable of driving up to 20 ISA backplane slots.
The availability of the PCI bus has dramatically extended the usefulness of the PC. However, the speed of the PCI bus is related to the chipset used on the CPU card. The newer chipset provides up to 100MB/s PCI transfer rate.
The new concurrent PCI architecture From Intel maximizes performance with simultaneous activity on the CPU, PCI and/or ISA buses. With a multi-transactional timer, enhanced write performance, a passive release mechanism and support for PCI 2.1 compliant PCI delayed transaction, concurrent PCI provides increased bandwidth, improves video and audio performance, and improves processing of host-based applications.
While PC makers are trying to cut the cost of chips for home use, the industrial market demands high performance and reliability. For the first time in years the performance of the industrial Intel-based Pentium computers is greater than that of the PC found in local stores. Clients looking for a higher performance system must question the type of chipset and the architecture of the CPU card.
PCI IN IPC
PCI bridging needed to provide additional (up to 16) PCI slots poses another set of problems. First of all, the design must adhere to the latest PCI 2.1 standard and must be crafted to be compatible with a high speed bus. The last thing users want is intermittent performance in the computer backplane. The field of the industrial computers has become complex enough to require professional assistance during the selection of the most appropriate system that will last in industrial environments over many years. Extension of the computer's life in the field can be a very challenging assignment unless you have no limit on your budget.
As long as you are prepared to accept that the ideal industrial computer won't be cheap, you have a good chance in finding a suitable extended system.
© MasTec Ltd