Brochure/Catalogue

Glossary
Threshold monitoring The limiting values of physical variables must be continually monitored for
industrial processes. This includes ll levels, temperatures, speed, positions,
weights and frequencies. Specialised threshold monitoring components are
used for this purpose. The sensor signals are captured on the input side,
evaluated electronically and converted. The corresponding threshold (min/max)
are then made available via the digital switching outputs (relays or transistors) to
the external devices. Potentiometers can be used to customise each switching
point and its minimum/maximum threshold as well as the switching hysteresis.
Transformer-based current
measurement
Signal converters with transformer coupling are used for taking cost-effective
measurements of sinusoidal currents (50/60 Hz). The current being measured
ows directly through the primary coil of the measurement transformer. It is then
stepped down and electronically processed in the converter.
True RMS value True RMS is the measure of the active component of alternating current and
voltages. The root mean square (RMS) is a measure of the magnitude of varying
quantities (such as alternating current and voltage). It is a constant value that
relates to the power consumed by a resistive load in a specied time period. The
RMS is dependent on the amplitude and the curve slope. Non-sinusoidal signals
can only be measured and processed with “true RMS”-compliant devices.
TTY The TTY interface is a serial interface. This interface is often referred to as a
20-mA-current interface since a constant DC current of 20 mA ows through
it during the idle state. In contrast to RS232, the data transmission for the
asymmetric signal connection is not controlled by voltage changes but by a
load-independent line current (typically 20 mA for High and 0 mA for Low). Thus
there is no signicant length-dependent voltage loss to take into consideration.
Here the cable lengths can run up to several kilometres.
TTY interfaces are currently used mostly where dedicated connections are
required: for exchanging data between electronic scales, for large industrial
displays, or for log printers.
Type of contact A contact is called normally open (NO) or a make contact if it is open when the
armature is dropped out (no current in coil) and closed when the armature is
picked up (current owing in coil). A contact is called a break contact or normally
closed (NC) contact if it interrupts the circuit when the armature is picked up.
A combination of NC and NO is called a changeover (CO) contact. A relay may
have one or more of such contacts:
NC – Normally Closed = break contact (11, 12: NC contact)
NO – Normally Open = make contact ( 13, 14: NO contact)
CO – Change Over contact (11, 12, 14: CO contact
(11 is the shared (root) contact))
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Technical appendix/Glossary
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