Каталог Weidmuller: Electronics - Analogue Signal Conditioning

Technical appendix/Glossary
Glossary
Isolation amplifier (active isolator)
An isolation amplifier is used to provide electrical isolation for analogue standard
signals. They are designed with 2-way or 3-way isolation. The isolation of the
potentials eliminates interference on the measurement signal that can be caused by
earth loops or common-mode noise. The active isolator makes use of a separate
voltage source for its power supply. It functions without feedback; a change on the
output side load does not influence the input circuit.
L
Leakage current
Limiting frequency
Line break monitoring
Linearisation
Load cell
Load resistance (load)
The current on the load side of an optocoupler that flows towards the output circuit
while in a closed state.
The limiting frequency of an analogue signal isolating converter is that frequency
where the output signal is reduced to 1/(sqr2) of the value of the input signal
(approx. 70.7 % = -3 dB).
Analogue measuring transducer with wire-break detection capability that
permanently monitors the input signal. In the event of an fault (a wire break), the
output signal jumps up to a defined value over the nominal range so that a controller
wired further down the circuit can evaluate the error.
Temperature-dependent components normally do not have a linear characteristic
curve. Their characteristic curves must be linearised so that they can be
evaluated as precisely as possible. The measurement curves of thermocouples
and temperature-dependent resistors (NTC/ PTC), in particular, exhibit significant
deviation from an “ideal curve”. In the linearisation process, the measurement signal
is processed by a microprocessor and an ideal characteristic curve is generated
which can then be analysed or processed further.
A load cell is a special type of force sensor used in weighing systems (i.e., with
scales). They are calibrated in grams (g), kilograms (kg) or tons (t).
Load cells usually have a spring mechanism used as a force sensor. The spring
is a specially shaped piece of metal whose shape changes slightly when under
the influence of weight. This elastic deformation is recorded by strain gauges and
converted into an electrical signal. Weights can be recorded ranging from a few
hundred grams to several thousand tons.
This is the load resistance on the output side of a measuring transducer or
transmitter. For analogue current outputs, the load is 500–600 ohms maximum.
Voltage outputs normally have a load of at least 10 kOhm.
W
M
Measurement isolating transformer
Converts electric and non-electric input signals into standard analogue signals. At
the same time it provides electrical isolation between the input and output (2-way
isolation) or between the input, output and supply (3-way isolation). Measurement
isolators are typically used to record temperatures (RTD, thermocouples) or for
measuring current, voltage, power, frequency, resistance and conductivity.
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