Brief Explanations of Technical Terms
Adjustment
The term often used in connection with calibration and meaning the steps necessary to keep measurement errors to a minimum, or at least smaller than the maximum permitted margin of error. This includes offset compensation and rising of the signals.
Amplifiers
ASCII
Short for American Standard Code for Information Interchange. This is the international standard for the allocation of characters to bytes ensuring that virtually all computers work to the same norms. Under ASCII each character is defined using 7 bits enabling 128 different characters to be defined. An 8th bit can be used as a parity bit or to create another 128 character set.
Calibration
A thermocouple, for example, can undergo changes due chemical or mechanical interference or aging. The extent of such changes depends mainly on the type of load to which the component is exposed. Therefore, temperature sensors need to be regularly calibrated. This means comparing temperature values against the actual temperature.
CAN bus
Controller Area Network - a serial bus system. Good data transfer capability over distances less than 40m with a transfer rate of 1Mbit/s. Theoretically unlimited number of participants but Message devices effective for up to 48 participants. Very reliable.
Configuration
Configuration means the system of computers, network or measurement data acquisition devices for a specific application.
For optimal user friendliness most systems can have their (operational) parameters pre-programmed, and then altered according to requirements. This pre-programming is known as configuration. Message devices can be configured from a PC via a network.
Controller
Controllers (at least PID controllers) enable the continuous control of process values. Available controllers are P, I, PI and PID.
As control path that part of a plant is defined which is between the final control element for influencing the control quantity (the process quantity to be controlled) and the measuring point of the control quantity. The final control element and the measuring element are also part of the control path.
Basically, control paths can be divided into two categories:
- Control paths with compensation: After a change of the control or interference variable the control variable strives for a new final value (steady state) e.g. flow, temperature etc.
- Control paths without compensation: Control paths not striving for a final value (integrating control paths) are called control paths without compensation e.g. liquid level.
Most control paths consist of P-systems (amplification/attenuation), one or more T1-systems (lowpass) and if possible one dead time (run time). Paths with P-T1 response are called control paths of 1st order. Control paths with several T1-systems correspondingly control paths n. order.
Data logger
An independently functioning data acquisition device for processing analog or digital measurement values, e.g. monitoring production processes.
Ethernet
Network for local use over distances from 10 metres to 10km. PCs are connected via coaxial cabling or twisted pair cables.
Data transfers take place from 10 to 1000 Mbit/s. The first Ethernet was installed used radio signals on Hawaii in 1973 and connected up radio stations on the various islands there.
FFT- / Frequency spectrum
Fast Fourier-Transformation (FFT). The Fourier-Transformation is a procedure for signal processing according to frequency.
The Fourier-Transformation transforms time-based signals into frequency-based signals. Frequency based data is easier to process for many operations. Delphin's AMDT/V module enables FFT calculation in the Message device itself. This means vibration calculations can be performed and evaluated within the device.
Galvanic isolation
Data acquisition and data logger devices must ensure its sensors and other components are protected against any electrical interference. Full galvanic isolation means full electrical isolation of all interface modules and channels.
Integrator channel
Is a virtual channel which establishes the integral of a signal. This can be used, for example, for establishing flow levels from flow rate measurements or energy supply levels from power measurements.
Master
A master is a centralized, processor based Bus participant which regulates communication and bus access of other (slave) devices within a network (e.g. in intranet applications). The base device (GBDT) undertakes the master function and the additional devices are the slaves in a CAN network.
Master/Slave principle
The master gives instructions, the slave follows instructions. A master can also give access rights to slaves.
Measuring transducer
A measurement device with an analog input signal and an analog output signal. The input signal can be a physical value of voltage, current, resistance or charge.
OPC
Stands for OLE for Process Control (communication standard for components in automation). The aim of OPC is to provide an open interface for Windows based technology for OLE, COM and DCOM, which enables a problem free, standardized data exchange between control/operation/monitoring systems, field equipment (e.g. Message devices), and office systems from different suppliers.
OPC-Server
Link between Message devices and any visualisation equipment which supports the OPC standard.
PID controller
Proportional, Integral, Derivative controller to enable the continuous control of process values. Refer to chapter "controller".
PLC programming
Programmable Logic Controllers - independent system for the controlling and regulating of processes. Programming complies to the IEC 1131-3 guidelines. Languages available are KOP, FUP or AWL.
Potential isolation
Potential isolation is a requirement in analog inputs to prevent electrical interference in sensors and other system components. Potential isolation between channels prevents, for example, ground loops, which can result in erroneous measurement values and can negatively affect the process. Analog inputs in Message device's are potentially isolated.
Process visualization
To make visible activity in industrial production, in the municipal sphere, in transport technology operations and in all laboratory and security fields of activity, i.e. to improve control over processes using a visualization system.
Profibus-DP
Field bus system for automation technology. A German national field bus standard for industrial automation (DIN E 19245). Profibus for Decentralized Peripherals (DP). Using Profibus-DP, simple digital and analog input/output groups as well as intelligent signal and process data units, can be transferred to on site locations. This means cost savings on cabling. Suitable mainly for time sensitive applications and in automated production systems. Message devices can be supplied with a Profibus interface.
Resolution
Every analog signal needs to be digitalised in order to be processed. The resolution is the measure for quantifying signals. Message devices have a 24 bit resolution.
RS 232 / serial interfaces RS 232
Recommended Standard Number 232. This is the oldest and most widespread interface standard. Its also known as the V.24 interface. High rate: 2 to- 6V, low rate: + 3 to 30V; approved cable length up to 15m; transfer rate up to 115 KBit/s; for point connection between 2 participants. TopMessage devices are equipped with 2 RS232 interfaces. They can also function as RS485/422 interfaces.
RS 485/422 / serial interfaces
Recommended Standard Number 485; high-rate: 1.5 to 6V, low rate : + 1.5 to 6V; Twinpair or Fourpair versions ; approved cable length of up to 1200m, transfer rate 10 Mbit/s. Up to 32 participants (sender / receiver) can be connected to a RS485-Bus.
RTD (100/1000)
Temperature sensor functioning on a resistance basis, i.e. the sensor's resistance increases with increasing temperature. Message devices measure these sensors using 4-conductor technology. In this way all output resistance can be eliminated.
The non-lineal relationship between resistance and temperature is taken into account by the Message devices.
Scaling
Measurement values such as pressure, temperature or power need to scaled according to a standard signal. There is lineal scaling, e.g. for pressure measurements, and non-lineal scaling as in thermocouples. Message devices provide for both types.
Signal conditioning
Signals with measurement values need to be converted to standard signal types, e.g. a pressure measurement converted from a 0/4..20mA signal or a temperature measurement from a 0..10V signal. Converters are used for such signal conditioning. These can be separate devices known as amplifiers. In Message devices, signal conditioning is already built in. Signals such as Pt100(0), thermocouples, mA or mV signals can be connected directly to analog inputs.
Slave
A slave is a data device controlled by a master device. Slaves cannot transmit without first being requested.
TCP/IP
Transmission Control Protocol - the accepted standard for data exchange in a heterogeneous network. TCP/IP can be used in local networks for communication between different types of hardware as well as providing LAN and WAN access. TCP ensures there is no data loss during data exchange. In contrast to the UDP protocol, confirmation is sent to the sender for every data package transmitted. TCP is allocated Level 4 in the OSI/ISO interface model.
10 BaseT
Star formed cabling emanating from a centrally active hub or switch. Twisted pair cabling of at least category 3 with a 100 Ohm impedance whereby data is transmitted separately according to send and transmit directions. Connectors used are 8-pole RJ45-types in which the pairs are connected to pins 1/2 and 3/6. Maximum length of a segment (i.e. from hub to end device) is restricted to 100m.
Thermocouple
Sensor used as temperature probe on the basis of the Seebeck effect. The thermocouple sensor can either be made up of two touching metals (soldered or welded), or as a semi-conductor. Thermocouples can be directly connected to Message device's analog inputs. A reference junction is provided.
Triggering
A signal which "triggers" a specific process, e.g. starting or stopping of data recording.
Validation
Evidence in line with regulations on good practice, that procedures, processes, equipment, materials and systems actually perform as they are expected to perform.
Virtual channels
Virtual channels provide additional functions for Message devices, increasing their functionality. In many cases, using virtual channels is the only method of performing certain tasks.