Interface boards

In order that the data acquisition system can obtain information about the spatial location and orientation of the probe, a four-channel incremental encoder interface board is installed. Three channels are used to define position in three-dimensional space, while the fourth monitors the skew of the probe (skew is defined as rotation about an axis normal to the probe face). Although six measurements are required to completely define the location and orientation, it is assumed that the probe remains in contact with the inspection surface. 

PCII/IIA interface board, and an IEEE-488 General Purpose Interface Bus may be used for communication. The internal command set of the PAR Model 276 interface allows for waveform generation to circumvent the requirement for analog programming. 

Step four in the interfacing operation is the use of computer software to communicate with a device and to capture the information it sends for analysis and display. This can be done at a basic level using machine language or higher programming tools such as Visual Basic, but increasingly this capability is provided by manufacturers of instraments, measurement systems, or interface boards. This relieves the user of much of the effort in interfacing devices and allows efficient and easy set up of different experiments typically done in physical chemistry laboratories. As illustration, we consider two examples of measurement approaches that can be used in a number of the experiments in this book. 

In addition, because the controller was integrated into the same assembly as the drive, the only board that needed to be installed in the computer was an adapter that converted signals between the motherboard and the drive/control-ler. The board is normally called a pass-through or paddle board. (This board is often, incorrectly, called a controller. The term is incorrect because the paddle board is often integrated with a floppy controller, two serial ports, a game port, and a parallel port. In fact, this combination is normally called a multifunction interface board.) With some of today s systems, the IDE adapter is integrated into the motherboard. 

Figure 13.15 shows the operational scheme of this automatic tltrator. The heart of the unit Is an INTEL 8080 microprocessor mounted on the central processing unit (CPU) board. The rotary reaction cell assembly can accommodate up to three different sensors for multiple measurements on the same processed sample. Each stepper burette board controls up to two burette dispensing assemblies. Function boards such as the colorimeter board, air burette board, E/I output board and RS-232 printer Interface boards are available optionally. The optional D/A and E/I board is used for closed-loop applications where the tltrator controls the final element such as a control valve. The RS-232 printer Interface board Is useful for troubleshooting the equipment and editing user-defined programs. The Instrument accuracy, repeatability and response time vary widely and depend on the particular type of measurement concerned. The system requires a.c. power, a 75-psl air supply and a dilution water supply for proper operation. The air flow-rate required is of about 50 cm3/mln... 

IBM 486 PC with GPIB interface board Other instruments used... 

SECM instruments suitable for imaging require a PC equipped with an interface board to synchronize acquisition of the electrochemical data with the movement of the tip. Building an SECM for kinetic experiments at fixed tip position or approach curve measurements is relatively easy, but fairly sophisticated software and some electronic work is necessary to construct a computer-controlled apparatus for imaging applications. Details on the construction of SECM instruments can be found elsewhere [6, 13-18, 53, 55]. An SECM is now available commercially from CH Instruments, Inc. (Austin, TX, USA). The instrument employs piezoelectric actuators, a three-axis stage, and a bipotentiostat controlled by an external PC under a 32-bit Windows environment. Various standard electrochemical techniques are incorporated along with SECM imaging, approach curves, and the modes described in Sect. 3.3.I.I. 

The detector includes a high-pressure mercury - xenon arc lamp, oriented perpendicular to the migration path, at the end of the capillary. The sample signal is measured with a photomultiplier and a photometer connected to the analog/digiial converter of a multifunction interface board, connected to a microcomputer. 

Fig. 3 A scheme of the LICRM setup operating under compressive stress, 1, Laser light source 2, movable corner reflector 3, polarizer 4 and 5, photocells 6 and 7, semi-transparent mirrors 8, stationary corner reflector 9, specimen 10, support 11, puncheon 12, clock-like scale micrometer for rough controlling deformation 13, dampers 14, figured lever providing a stress constancy 15, load 16, oil damper 17, cooling unit 18, heater 19 and 20, programmable temperature regulator 21, amplifier 22, tape recorder 23, oscillograph 24, shaper of a meander (Schmitt trigger) 25, computer with the interface board imbedded...

Errors in the Electronic Thermocouple Calibration The thermocouple interfaces with the computer via an analog-to-digital conversion board. Since the thermocouple s output is in millivolts, the interface board will linearize and set the limits of the signal. The instrument usually also will... 

The status of the actuated equipment is transmitted by the ILC s over the data highway to be displayed on the Main Control Board. The actuation logic is implemented by three redundant microprocessors and the actuation signals are voted in a 2/3 Logic in the power interface boards. Built-in automatic tester is provided for each ILC. 

The RIG signals were recorded on a chart recorder and collected via a laboratory interface board (CBM Data Acquisition and Control Adapter, IBM, Boca, Raton, FL) with a personal computer (Leading Edge, model D, Canton, MA). 

Advanced servo gauges and radar gauges can be provided with an interface board that communicates directly with the smart pressure transmitter. The result is a unique and very complete measurement providing level, interface levels, product-water interface levels, average density, average temperature, vapor temperatme, and alarms. 

In summary, all items should be checked for proper optioning to permit successful Installation. Both devices have to be SETUP to match each other. For example, if one device is set to 4800 bps, the other one has to be set to the same baudrate. The same has to be done with all other items listed above. In most cases these changes can be done either by DlP-swltches located on the interface board or by software in a PC. 

As a typical example, we will take the interface board of a MCA 35+ from Canberra. Fig. 10.4 shows you the circuit diagram where A69 is the USART, A57 is the transmitter, and A67 is the receiver. 

Next you have to provide the options in your computer to the setup chosen on the serial interface in the MCA. You will find a detailed description on the setup of the interface board in the Operators Manual of the MCA. Take care you cannot exceed a baudrate higher than 4800 bps, because no handshake is supported. 

STD-Bus Digital Input Boards. They should be reliable general purpose STD-bus interface boards, which provide an adequate number of 8-bit parallel input ports. It is used by the trip unit to get digital signals from its unshared single... 

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