isolated current voltage transducers

Glossary A-Z
Open loop current transducers (§ 3.1)
Current transducers where the output signal is an image of the
magnetic field created by the primary current to be measured. It
generally uses a magnetic circuit which focuses the field on a field
sensing element, e.g. made of a Hall generator. The output signal is
a direct amplification of the Hall signal, giving a true image of the
measured current if the system is designed for a linear behavior.
Primary
The input, driving or measured side of a circuit and the components
related to that side of the circuit. Galvanic isolation is provided
between the primary and the secondary side. For example, the
primary winding carries the primary current. See also Secondary.
PWB (printed wiring board)
Often referred to as a „PCB“ or printed circuit, or PWB depending
on the geographic location.
Ratiometric
The output (offset and/or transfer function) is directly proportional to
the supply or a reference voltage. See also Offset and Transfer
function.
Reaction time
The delay between the measured signal reaching 10% of final value
and the output signal reaching 10% of final value. See also
Response time, and Rise time (Figure 8).
Recovery time
The time required to ‘recover’ and resume normal operation after an
event that interrupts operation, such as saturation. Not to be
confused with Settling time.
Remanence
After traversing a hysteresis loop the output will not return to zero
when the input is at zero. The amount remaining at the output is the
remanence and, in essence, creates an additional output offset.
See also Magnetic offset and Hysteresis.
It is minimized by design in LEM transducers and is often resulting
from a non-expected primary current overload. The magnetic offset
defines the offset on the transducer output signal, positive or
negative depending on the direction of the current overload.
Response time
The time difference between the driving signal reaching 90% of its
final value and the measured signal reaching 90% of its final value.
This is a combination of delay time, driving signal rise time, and
measured signal rise time. See also Reaction time and Rise time
(Figure 8).
Rise time
The time difference between a signal reaching 10% and 90% of its
final value. See also Delay time, Reaction time, and Response time
difference (Figure 8).
Saturable inductor
An inductor designed to operate into its saturation region. The
inductance value varies from a high value at low currents (based on
the permeability of the core) to a low value at high currents (the
core permeability becomes unity when saturated). (Figure 25).
Secondary
The output, driven or measurement side of an isolated circuit and
the components related to that side of the circuit. Isolation is
provided between primary and secondary side components. For
example, the secondary supply provides secondary compensation
current. See also Primary.
Settling time
The amount of time required to ‘settle’ to within a defined tolerance
after a disturbance, such as dv/dt. Not to be confused with
Recovery time.
Standard Fluxgate
A LEM definition, Standard Fluxgate transducers operate on the
closed loop principle and provide the most „standard“ performance
in term of accuracy or bandwidth. Non-standard Fluxgate
transducers include the more efficient IT or C-types, or the less
dynamic „low frequency“ Fluxgates. See also C-type, IT-type,
Fluxgate, Low frequency Fluxgate and § 4.
Transfer function
The ratio of output signal to input signal. For example, if a 100A
input creates a 1V output the transfer function is 1V / 100A or 1mV /
100mA. The output of a ratiometric device is dependent on the
supply voltage, so VS will be part of the transfer function.
Turns ratio
The ratio of primary turns to secondary turns in a transformer. With
closed loop current transducers, the turns ratio typically assumes a
single primary turn. For example, 1:1000 implies 1000 secondary
turns and a secondary current of 1mA with a single primary turn
carrying 1A.
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