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The microprocessor compares the value measured
with the characteristic curve for the thermocouple in its
memory and calculates the corresponding value on the
“ideal characteristic curve”. At the output, it supplies
the latter to an amplier, which produces the analogue
value in linear form. The output stage converts this into
a standardised value or into a switching output with a
switching threshold.
The linearisation of PT100-elements can be undertaken
via simple amplier stages. The rst stage corrects
the peak value of the graph of the measurements. The
deviation at the end of the graph resulting from this
is corrected by a second stage. The under- and over-
shooting generated in this way is very slight and is
covered by the tolerance for the module.
Current Measurement Using A Measuring Transformer
• Transformer principle: Each conductor through which
current ows is surrounded by a magnetic eld H, the
intensity of which is proportional to the current. The
eld, which is bundled in a magnetic core, generates a
magnetic ux B, through which suitable sensors are used
to measure current.
Converters with transformer-type couplings are used to
establish the most cost effective measurement method
for simple sinusoidal currents. The current to be measured
ows directly through the measuring transformer‘s
primary winding.
The secondary winding supplies the measuring
electronics with a proportional current signal. Because of
power loss this method of measuring current is limited
to smaller currents up to 5 A. These converters react
sensitively to peak loads and therefore have to be fused
on the primary winding side.
Measuring Current Using A Hall-type Sensor
• Hall-type sensor principle:
Hall-type sensors also measure the magnetic ux B and
supply a proportional voltage at the measured output,
which is then reconditioned to form a standard signal by an
amplier circuit.
• Components with Hall-type sensors are ideally suited to
measuring higher currents, as any possible high residual
currents from motors or peak loads cannot damage the
component. Additionally, they are also ideal for measuring
direct and alternating currents of various curve shapes.
Root Mean Square Measurement / Crest Factor
• The root mean square value (r.m.s) of a sinusoidal shaped
alternating current is the value, which in an ohmic resistor
converts the same (effective) output as that of an equal
sized direct current.
• Non sinusoidal shaped signals can only be measured with
“True RMS” capable devices and/or further processed.
• True RMS = True root mean square
• Root mean square measurement is required where the
(effective) output content of alternating voltages or
currents are to be measured or evaluated.
• The crest factor indicates the ratio of the crest factor to
the root mean square value.
Technical data
W
Technical appendix/Glossary
W.8 2729490000