80224_MHW_650 L - 1250 L_07-2018_ENG - 4
INTRODUCTION
Symbols used in this manual
Glossary
Pay attention when you see these symbols in the manual.
Indicates very important information on correct
product function or on safety, or an instruction that
MUST be followed.
Indicates risk for the safety of the installer or user
due to the presence of high voltage.
Indicates a point to which the reader’s attention is
called.
Indicates a suggestion that could be useful for
better use of the device
Indicates a reference to other technical documents
that can be downloaded from www.gefran.com.
WWW
4...20 mA
Current used as signal transmitted by
certain sensors or in a specific way to
control a device, such as a motorized
valve.
Alarm
Output that trips when a certain condi-
tion is reached, for example, a defined
temperature
Hysteresis
The phenomenon in which the value of
a physical property lags behind changes
in the effect causing it, as for instance
when thermocouples temperature lags
behind the heater temperature
Pt100
A commonly used temperature measu-
rement device. At 0°C its resistance is
100 ohm, normal extension cables can
be used.
PV
Acronym for Process Value, i.e., the value
that the process variable (temperature,
valve opening, etc.) has at that moment.
Sensor
Device that translates physical phe-
nomena (such as change in resistance
based on temperature) into electrical si-
gnals that can be acquired and proces-
sed by the indicator
Thermocouple
Sensor that transmits an electrical signal
of a few millivolts. It needs specially de-
signed extension cables