Prospect of bus technology in instrument control and connection

Over the past two decades, scientists and engineers have widely used IEEE 488 and GPIB in automated instrument systems. When popular computer technology enters the field of test and measurement and uses bus technologies such as USB, Ethernet, and IEEE 1394 when connecting the instrument, whether the GPIB interface can become the first choice for the instrument control bus interface in the future becomes a question. Because GPIB has powerful functions and a broad user base, GPIB will continue to exist for many years to come. However, the instrument control industry is likely to start entering the world of hybrid I / O systems. This paper discusses the future development of the instrument system when GPIB is used in combination with other buses, and the importance of software "upward compatibility" in instrument control.

GPIB basics

GPIB is specifically designed for instrument control applications. In the 1970s, the birth of the IEEE 488 standard led to the production of GPIB standards for electrical, mechanical, and functional specifications in 1975; in 1987, ANSI / IEEE standard 488.2 more clearly defined the method by which controllers and instruments communicate via GPIB. Make the previous specifications more complete. GPIB is a digital 8-bit parallel communication interface with a transmission rate of 8Mbyte / s. A controller provided by the bus can connect up to 14 instruments within a 20-meter cable length. However, if users use GPIB amplifiers and extenders, they can break through these two limitations. GPIB cables and connectors are a multi-faceted product that meets industry standards and can be used in any environment.

Advantages of the new bus technology

In the past, computers only provided serial (RS-232) and parallel ports. In recent years, computers are equipped with Ethernet, USB (Universal Serial Bus), and sometimes even IEEE 1394 (FireWire) interfaces. These new buses have many attractive features-easy to use (USB), easy to connect (Ethernet), and high speed (IEEE 1394).

USB

The design of USB is mainly used to connect peripheral devices such as keyboards, scanners, and disk drives. Apple Computer pioneered the use of USB as its only serial port in 1998. In the past few years, the number of USB-connected devices in the computer industry has greatly increased.

As far as the current USB1.1 specification is concerned, the data transfer rate has reached 1.5 Mbyte / s, and the next generation of USB products will use the USB2.0 specification, which will increase the bus data transfer rate to 60 Mbyte / s. The USB2.0 specification is compatible with USB1.1 devices, and even the same connector can be used. Because the universal serial bus is a plug-and-play technology, whenever a new device is added, the USB host will automatically test and identify its identity, then adjust its configuration appropriately, and an interface can control 127 devices at the same time. For the Windows operating system, the USB connection is currently only available on Windows 2000 / XP / 98.

USB has the advantages of low price and easy connection between the instrument and the computer. In addition, USB provides more convenient serial port functions such as: hot swap, built-in operating system fine-tuning function, high flexibility, etc., to improve the traditional serial port technology.

Although USB has many attractive advantages, it also has some disadvantages in terms of instrument control. First of all, the USB cable has no industry standard specifications. In a noisy environment, it may cause the loss of data. In addition, the USB cable does not have a locking mechanism-the cable may be easily removed from the computer or instrument. The length of the cable (including the use of online repeaters) can be up to 30 meters; finally, there is no industrial transmission standard for USB in instrument control, and it must be designed by the instrument manufacturer.

Although USB has some shortcomings, due to the widespread use of computers and the high speed of USB2.0, it has become the leading pioneer of instrument control in the future. Although few instruments currently provide USB control options, users can connect their instrument control applications through a bridge and USB. The bridge provides users with a bridge between USB and GPIB. The bridge will be discussed later in this paper.

Ethernet

Recently, instrument manufacturers have begun to use Ethernet as another communication interface option for individual instruments. Although Ethernet is still a new application technology in instrument control, it has been widely used in other aspects of measurement systems as a mature technology. There are more than 100 million computers in the world with Ethernet function, making it an inevitable trend for the Ethernet network as instrument control.

Ethernet-based instrument control applications can take advantage of the characteristics of bus technology, including instrument remote control, resource sharing within the enterprise, and convenient report generation. In addition, users can make full use of the existing Ethernet network. However, this advantage may also cause problems for some companies, because it will force network administrators to involve traditional engineering applications.

To use the Ethernet network for instrument control, the following factors need to be considered: transmission rate, decisiveness, and security. The most common Ethernet transmission rate is 10BaseT or 100BaseTX, respectively reaching transmission rates of 10Mb / s and 100Mb / s. However, these transmission rates are rarely achieved due to the traffic of other networks, fixed usage, and insufficient data traffic. The uncertainty of the transmission rate determines that the communication on the Ethernet network cannot be confirmed. Finally, in the face of sensitive data users, there must be further security measures to ensure data integrity and privacy.

IEEE 1394 (FireWire)

The IEEE 1394-1995 standard, also known as FireWire (registered trademark of Apple Computer), is an efficient serial bus developed by Apple Computer in the 1980s. The current data throughput rate of IEEE 1394 can reach up to 50 Mbyte / s. But the IEEE 1394 Trade Association is revising its specifications and intends to increase the data transfer rate to 400Mbyte / s. According to the 1394 specification, the bus connection of the device must be within 4.5 meters, then the connection of 16 instruments will also be within 72 meters. In the Windows operating system, only Microsoft's Windows 2000 / XP / 98 is compatible with 1394.

The IEEE 1394 bus provides great potential for high-speed transmission applications. Many digital cameras and other consumer electronics products already include the IEEE 1394 interface for data transmission. The high bandwidth of IEEE 1394 provides a feasible solution for complex multimedia applications. IEEE 1394 has more advantages than USB. It has a transmission protocol specifically defined for controlling instruments in bus technology. However, currently only a few instruments have a 1394 interface.

Although IEEE 1394 has many advantages in instrument control, such as high bandwidth, there are still some factors that hinder its current development. The main disadvantage of IEEE 1394 is that the 1394 interface is not built into the periphery of Intel ’s PC integrated chips (all Macintosh computers have a built-in 1394 interface). Therefore, Intel PC users must connect an external 1394 controller, especially for PCI boards. Although the FireWire cable is lightweight and flexible, it does not meet industry standard specifications, so it may cause data loss in some test and measurement applications.

Spin Bike

Spin Bike,Magnetic Spin Bike,Proform Spin Bike,Indoor Cycle Exercise Bikes

ZHEJIANG POWERTECH CO,.LTD , https://www.zjpowertech.com