Actuator sensor interface

The development of this type of technology has reached the stage where there are safety certified bus systems on the market. For example the actuator sensor interface (ASI) system in the form supplied by Siemens is fully certified for safety duties in machinery applications. This system is relatively simple in that it is designed for binary devices only. See www.ad.siemens.de/safety. 

Problem A safety instrumented function uses three analog transmitters as process sensors, a safety PLC and two remote actuated valves interfaced to the PLC with 24 VDC three way solenoids. What portion of the safety PLC is used in this safety instrumented function ... 

During the second semester of the sequence, the robot parts were either fabricated in-house, or purchased, and the structure was assembled. The EE s developed their system-level design into circuit and software details, and then built and programmed the control system. They completely built a bus based multi-processor system, with one Intel 8085 microprocessor for digital PID control on each of the three cartesian axes, one 8085 to handle the gripper and sensor inputs, and one 8085 to coordinate communications on the bus and to a host personal computer. They also designed and built sensor interfaces and pulse-width-modulated power amplifiers for the dc motor actuators. 

Figure 6. Left Conventional control loops provide a localised interface between the real and the digital world. Sensors targeted at important control parameters feed information into digital control routines that can respond via actuators e.g. to maintain parameters within specified limits. Right A vital step on the route to the realisation of the concept of internet scale sensing is to adopt the principle that all analytical measurements should be capable of being internet-linked. The localised control of important parameters is maintained, but the information is shared via the internet with external users [4]. (Reprinted with permission from Anal. Chem., August 1, 2004, 75 (15), 278A-286A. Copyright 2004 American Chemical Society.)...

The central computer is called the master terminal unit, or MTU. The MTU has two main functions to periodically obtain data from RTUs/PLCs and to control remote devices through the operator station. The operator interfaces with the MTU using software called human machine interface (HMI). The remote computer is called the program logic controller (PLC) or remote terminal unit (RTU). The RTU activates a relay (or switch) that turns mechanical equipment on and off. The RTU also collects data from sensors. Sensors perform measurement, and actuators perform control. 

W. Bracke, P. Merken, R. Puers and C. Hoof, On the optimization of ultra low power front-end interfaces for capacitive sensors, Sens. Actuators A Phys., 117(2) (2005) 273-285. 

The modular backbone introduced here allows both commercial and demonstration-type micro structured devices to be coupled in all three dimensions in a flexible and easy manner. Micro structured heat exchangers, reactors and mixers of different manufacturers are surface mounted on this backbone. Owing to the standardized interfaces, devices can easily be exchanged, for example, to evaluate different types of mixers. The backbone itself consists of elements which can be combined individually and flexibly in all directions, according to the demands of the plant to be built. The backbone provides the flow paths for fluids and electrical conduits for power supply and signal transmission of sensors and actuators. 

B. E. Boser, in RE Analog-to-Digital Converters Sensor and Actuator Interfaces Low-Noise Oscillators, PLLs and Synthesizers, W.M.C. Sansen, R.J. van de Plas-sche, J.H. Huijsing (eds.), Kluwer Dordrecht, 1997. 

Recently, several things have pointed to a resolution of the NeSSI-bus issues. First, for the past few years there has been an effort under way at NIST called IEEE 1451 (http //www.motion.aptd.nist.gov/). The IEEE 1451, a family of Smart Transducer Interface Standards, describes a set of open, common, network-independent communication interfaces for connecting transducers (sensors or actuators) to microprocessors, instrumentation systems, and control/Iield... 

Stage 2 At this stage the structure of the sensors, actuators, and individual components is the same as in Stage 1, but the individual components may be connected to a data processing computer via a data interface. Monitoring and operation is again the responsibility of the shift personnel. 

Mizsei, J. (1995), H2-induced surface and interface potentials on pd-activated Sn02 sensor films. Sensors and Actuators B Chemical, 28(2), 129-33. 

De MarceUis, A., Depart, A., Ferri, G, Flammini, A., MarioU, D., Stornelli, V. and Taroni, A. (2008) Uncalibrated integrable wide-range single-supply portable interface for resistance and parasitic capacitance determination. Sensors and Actuators B Chemical, 132,477-484. 

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