Contents Norgren Pneumatic Valve Products

Glossary
Address – Part of the message sent by the Fieldbus Controller is concerned with
the device address. Each address is unique, and specifies the location of each valve
driver and the solenoid position for the valve.
Analogue / Digital – Analogue signals are continuously variable (as is sound in the
real world). Computers find it difficult to use analogue signals, so signals are
converted into a digital form.
ASIC – Application Specific Integrated Circuits. These are designed for electronic
circuits for use within a specific Fieldbus system. i.e. an ASIC for one type of system
cannot usually be used with another.
Baud Rate – The speed at which digital information is transmitted. Baud rate is
measured in bits/sec.
Bi-directional – Refers to the fact that messages can be sent in both directions
along the same wires.
Binary – A mathematical system whereby the digits 0 and 1 are used to represent a
character or piece of data in a computer. The electrical signals inside the computer
can be thought of having only two states; signal off and signal on (0 and 1
respectively).
Bit/Byte/Word – A bit is a computing unit expressed as a choice of 0 or 1 (in basic
terms - signal off or on). Bit actually stands for Binary Digit
Byte – A group of eight bits. The lowest bit (rightmost)_ is equal to 0 or 1 and the
highest bit is equal to 0 of 128. The highest value that one byte can represent is 255
(or 256 states). i.e. 128 + 64 + 32 + 16 + 8 + 4 + 2 + 1 = 255
Word – A group of sixteen bits. Words are used in 16 bit computers and many PLC
data stores. A word can represent in binary form a maximum value of 65535 (or
65536 states).
Communication Bus – A physical link over which data is transmitted between
suitable devices. The bus may be a wire, fiber optic, or radio wave.
Diagnostics – A way of receiving information on faults or problems between
devices. This is achieved by using visible indicators on or inside the Fieldbus unit or
by communication between devices. i.e. if a program finds a fault, it may be
instructed to reset the system or possibly to wait for further instruction from an
operator.
Fieldbus – Also bus. A data link (usually in the form of a cable) on which electrical
devices communicate with each other for control purposes. In Pneumatic systems,
Fieldbus linked drivers, operate valves or other remote devices. Feedback from
sensors is provided by Input Modules.
Hexadecimal – A mathematical system where each character can represent a value
up to 15 (i.e. 16 states). i.e. Hex 0,1,2,3,4,5,6,7,8,9,A,B,C,D,E,F.
I/O – Also Input/Output. The I/O is the physical connection between a controller and
the equipment that it controls. The connected inputs may be switches, proximity
devices or analogue sensors. Outputs may be relays, pneumatic solenoid coils or
analogue devices. The Input module also serves as a barrier against harsh spikes
and noise often experienced in an industrial environment. It may contain optoisolators
which protect the CPU from large input surges.
IP rating – Provides a means of classifying the degrees of protection from dust,
water and impact afforded by electrical equipment enclosures. It is common practice
for manufacturers to apply ratings for only the first two numerals.
IP40 and IP65 – IP40 protects against solid objects over 1 mm (such as tools, wires,
fingers), but has no protection against ingress of liquids. IP65 totally protects against
dust and low pressure water jets from all directions.
Ladder Logic – A method of describing an electrical circuit in logic symbols and
relay-based ladder diagrams. It is the usual way to program PLC’s.
Line Bus – A line bus does
Master – A controller connected to a bus which issues messages to other devices
on the same but. Masters contain programs to logically control processes and can
be a PLC, PC or other control device.
Supervisory Master – A controller which only concerns itself with the inputs and
ignores all the outputs.
PLC – Programmable Logic Controller
Slave – A device connected to a bus which only responds when a message
intended for itself is received. Except for a reply to that message, it can not access
the bus. The common name for the valve driver or input module.
Repeater – A device which can either boost the signal generated by a fieldbus
master (in order that slaves can be positioned further from the signal source): or it
may allow a greater number of devices to be connected to a Fieldbus system.
Valve Manifold – Replaces the manifold solenoid valve bank. A combination of
system valves, usually with a multipole, configured specifically to meet customers
needs.
Gateway – A converter which allows systems running two different protocols to
communicate with each other: in effect a translator.
Ladder logic – A method of describing an electrical circuit in logic symbols and
relay-based ladder diagrams. It is the usual way to program PLC’s.
Line bus – A line bus does not form a closed loop circuit.
With the line bus networks Norgren promotes, all the
stations are daisy chain together to overcome a problem
associated with Spur distances. Although both a line-in and
line-out are provided, they are effectively connected inside
the Fieldbus units. However, DeviceNet units tap directly off
the communication bus with t-pieces.
Ring bus – Also Closed loop. All stations in a system are
linked into a physical ring. With Interbus-S the link passes
through each station in turn and each station is therefore an
integral part of the transmission path. The data makes one
trip around the ring, passed from station to station. Each
station checks whether the data is addressed to it. When
this is the case, the station copies the data into its own
memory.
Tree bus – Does not form a closed loop. Each station is
linked to the transmission path by cables as required. Unlike
Line bus, a Tree bus is more flexible because the
communication can be laid out into any convenient shape.
Multi-drop – Refers to a communications system which has
two or more devices connected to it off a bus (i.e. more than
one device can be connected to it).
NEMA 4 – An American Standard for water penetration.
Multipole – A connector in which all the individual wires for
devices are combined in a cable which has en integral multipin
connector for quick connection and installation in a
system. i.e. a printer cable for connection to a computer
employs a similar principle.
Noise – Electrical interference, usually in the form of high
voltage spikes or radio signals caused by unscreened or
unsurpressed equipment. Noise can cause corruption of
data during transmission or malfunction of electronic
components.
Open System – For a system to function properly, all
devices must be compatible. With Open systems, the
technology (or protocol) is available to allow manufacturers
to build compatible equipment.
Closed System – Also In-House or Proprietary system. A
manufacturer develops the technology (or protocol) that is
unique to him. Closed systems are therefore company
specific and usually non-compatible with other types. Closed
Norgren systems are: Pneubus, Sysmac, Jetterbus.
Opto-isolator – Separates harsh industrial signals from
sensitive components in a controller or slave. This is
achieved by converting the signal to light. The external
signal is transmitted as light to a light sensitive receiver.
This in turn converts the light back into an electrical signal.
Protocol – Defines the content and structure of a Fieldbus
message. The differences between each Fieldbus protocol
can be considered in the same way as those between
languages.
RS232, RS422, RS485 – American Standards for the
electrical characteristics of a link. The standard specifies the
digit state values. Links are used in the digital transmission
of data between electronic equipment.
RAM / ROM / EEPROM –
RAM – Random Access Memory. RAM is used internally
by a PC or PLC as a short term store for data, program
variables and control codes. It is volatile and as such will
lose all its data when power is removed. Therefore, RAM
used for programs is battery backed.
ROM – Read ONly Memory. ROM is pre-programmed by
the manufacturer. It holds the controller system memory
and instructions for its operation. It cannot be altered. It is
non-volatile; when power is removed a ROM retains all its
information.
EEPROM – Electrically Erasable Programmable Read
Only Memory. EEPROM’s are used to store the user
program. They can be erased and programmed with
relative ease. As with ROMS. EEPROM’s do not lose their
contents when power is removed and as such they are
non-volatile.
Littleton, CO USA Phone: 303-794-2611 www.norgren.com VAL-2-41