PD IEC TS 62098:2001 pdf download
PD IEC TS 62098:2001 pdf download.Evaluation methods for microprocessor-based instruments.
4.1.1.5 Communication Interface
The communication interface provides means for either parallel or serial communication by a digital communication link to a data acquisition system, a distributed control system or a hand terminal for local read-out.
4.1.1.6 Power supply assembly
The power supply assembly receives either an unregulated ac. or d.c. supply voltage. It provides stabilised and regulated supply voltages andlor currents (either ac. or dc. or a combination) to the various parts of the instrument.
4.1.2 Listing of Instrument functions and attributes
In general, an instrument user is only interested In the overall functions of the above-mentioned Information flow routes (from boundary-to.boundary). However, when possibilities exist In the instrument to make measurements Inside that black box, they shall be considered. If instrument problems arise during an evaluation, these measurements can be of great help in diagnosing the cause and curing possible design faults. Therefore, based on the above division of an instrument into subsystems, we need to further detail the functions and their attributes to obtain an overview of the capabilities.
It shall also be realised that the number of functions defined to be evaluated has an effect on the time required for an evaluation and the costs.
From the model of figure 4 the following main function groups can be identified:
– measurement functions:
output functions:
data processing and control functions:
– communication functions:
– human interface functions;
– supervisory functions.
4.1.2.1 Measurement functions
— Number of quantities to be measured
— Measurement ranges
Adjustment options (may be resident in data processing unit)
Cycle times
Filtering for electrical signals
– Sensor attributes used:
• thermocouple, resistance temperature detector (RTD), pulse rate, strain gauge, V. mA etc.;
• characteristic: linear, logarithmic, quadratic. etc.:
• self-powered or requiring power;
– Split architecture (sensor assembly separated from other subsystems)
4.1.2.2 Output functions
一Number of output channels
一Type of output signals
analogue: electrical (mA, V), pneumatic, hydraulic
binary: relay, solid state
pulse rate (frequency, amplitude, shape)
Adjustment facilities
一Load rating (voltage, current, load impedance)
4.1.2.3 Data processing and control functions
Processing capacity in combination with a minimum cycle time
-Task priorisation and timing
Application software, function block structure:
. Time-dependent function blocks:
一control (e.g. PID)
一lead/lag
一totalisers, timers
-velocity limiter
bandfilters
。 Time-independent function blocks:
-calculatory
一polynomial
– logical functions
一hillo selectors
一alarm functions (hi, lo, velocity, deviation)
statistical functions
一Data storage capacity
4.1.2.4 Communication functions
一Cycle time
-Buffer size for data transfer
-Transmission speed (throughput)
-transmission medium
4.1.2.5 Human interface functions
Setpoint control: local, remote
-Mode control: auto/manual, cascade
一Trend storage and replay
Condition monitoring (see also supervisory functions)
— Parameter control: PlO, bias, measurement range, alarm levels
4.1.2.6 Supervisory functions
Self-test functions wilti checks for:
• internal failures (processor, memories, data transfer),
• communication failure,
• line break, power failure,
• maintenance prediction;
– Configuration (programming) function: offline, online
4.1.2.7 Supply function
– Electrical, pneumatic, hydraulic
Filtering. stabilisation. regulation
4.1.2.8 Environmental int.rfac. function
The interface provides protective measures against environmental influences such as:
– ambient temperature (e.g. ventilation);
– vibration (passive or active dampers);
– water and dust (enclosure design as defined per IP-protection class);
– electrostatic discharge (anti-static paint).
4.2 Instruments on a digital communication link
For the purpose of an evaluation three types of instruments are Identified In figure 5:
– measuring instruments.
– process controllers.
intelligent actuators.
Measuring instruments in such a configuration do not necessarily need the output system that provides an analogue output. On the other hand, actuators receive digital information for controlling the final control elements.
We can further expect that the functionality to be expected or realised in each of the three types can differ considerably from manufacturer to manufacturer,
Some measuring instruments provide only the measurement function, whereas other measunng instruments may include a control function or a supervisory function and send their output signal over the digital communication link to the computer and/or an actuator. The operator then provides the controller setpoints by means of the computer,
Actuators may be equipped with the controller function.
The process controller shown in figure 5 may be equivalent to classical instruments.
In a digital communication system, It can be expected that instruments will be supplied that have no facilities for local read-out and manipulation of parameter settings etc.
