19"
In instrumentation and control engineering the term rack (actually 19-inch rack) stands for a frame
with a standard width of 19 inches. Individual drawer units or panels having front-plate widths of
exactly 48.26 cm (e.g. PC board carriers) can be mounted in such racks.
One height unit (HU) is specified as being 1.75 inch (4.45 centimetres).
19" racks are standardised (EIA 310-D, IEC 60297 and DIN 41494 SC48D) to allow the installation
of any types of units as long as they comply with these referenced standards.

ARINC 429
ARINC 429, a generally recognised standard from the company ARINC (Aeronautical Radio,
Incorporated), was developed in the 1970s and is used as a communications protocol for aircraft
electronics. The measurement data of various aircraft systems, for example motor and flight control
elements (fly-by-wire), can be connected with one another over the ARINC429 system bus.

Data word structure:
a) bits 1...8: label bits (octal and inverse)
b) bits 9...10: SDI (source destination index)
c) bits 11...29: data area
d) bits 30...31: SSM (sign status matrix)
e) bit 32: parity

Example: Label 142 octal (decimal 98; binary 1100010)
eddcccccccccccccccccccbb0100011

A distinction is made between low speed (12.5 kbit/s) and high speed (100 kbit/s) transfer rates.
At the low speed transfer rate a tolerance of 10 % is permissible, at high speed transfer rate the
tolerance is 5 %.

ARINC429 is based on three voltage levels: -10 V, 0 V and +10 V
For each bit transferred, half of the time for the bit voltage will be at +10 V for a "1" or -10 V for a "0",
the second half of the bit's time voltage is to be at 0 V.

The minimum idle time (GAP time) between two 32-bit messages is 4 bits.

CAN
CAN is an asynchronous, serial bus system developed in 1983 by Bosch for networking control
units in automobiles. Together, Bosch and Intel presented CAN in 1987 as a means to reduce the
length of cable trees (up to 2 km per vehicle) and thereby save weight.

cRIO
cRIO is a designation of the company National Instruments for "compact reconfigurable I/O".
The National Instruments Internet homepage contains the following description of cRIO:

"RIO technology (RIO = reconfigurable I/O) from National Instruments permits user-specific
adaptations of FPGA-chip-based instrumentation and control circuitry by means of the graphic
development tool NI LabVIEW. At the core of RIO hardware is an FPGA chip and its peripheral
circuitry that allows LabVIEW to impose a hardware synthesis."

Realtime
The expression "realtime" means that a system must react to an event within a prescribed amount
of time.

FPGA
FPGA is the acronym for Field Programmable Gate Array, the designation for a chip that can be freely programmed.

LVDT
LVDT is the acronym for linear variable differential transformer.
This device consists of a primary coil and one or two secondary coils.
Depending on the number of coils, they are typically referred to as 4-wire LVDT (one secondary coil)
or as 6-wire LVDT (two secondary coils).
The excitation voltage on the primary coil is transferred into the secondary coils under the influence
of a moveable iron core. Depending on the iron core's position, various different voltage amplitudes
will be produced in the secondary coils. An evaluation of these amplitudes makes it possible to
determine the iron core's exact position.

PCB board
"PCB board or PCB" is an acronym for "printed circuit board".
A printed circuit board consists of a carrier of insulating material onto which electrically conducting
interconnect paths are permanently bonded. The printed circuit board serves as mechanical fixation
as well as electronic interconnection for the components mounted on the board.

Resolver
A resolver is a type of rotary transformer used to measure degrees of rotation. It does this by
converting changes in angular position into an electric quantity.

RS232
RS232 is a standard for serial interfaces capable of bit-serial data transfer.
The typical voltage levels are -12 V for a logical "0" and +12 V for a logical "1".
A data word consists of a start bit, 5...9 data bits, an optional parity bit and a stop bit.
Typical transfer rates are 2400, 4800, 9600, 19200, 57600 and 115200 baud.
With increasing data transfer rates the maximum cable length of 900 m drops to <2 m.

The pin layout for RS232 connectors, D-SUB 9-pole and D-SUB 25-pole are shown below:

Conversion table for D-SUB25 to D-SUB9

DB9	DB25	Functions
1	8	Data Carrier Detect
2	3	Receive Data
3	2	Transmit Data
4	20	Data Terminal Ready
5	7	Signalmasse
6	6	Data Set Ready
7	4	Request To Send
8	5	Clear To Send
9	22	Ring Indicator