Typographical Conventions Used In This Manual; Glossary - gefran 850 Installation And Instruction Manual

Typographical conventions used in this manual

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

Glossary

4...20 mA Current used as signal transmitted by cer-
tain sensors or in a specific way to control
a device, such as a motorized valve.
Allarme Output that trips when a certain condition is
reached, for example, a defined temperature.
Auto Tune
Function that lets you calculate and easily
set the P, I and D parameters thanks to the
controller's self-learning.
Cool
Control used for cooling.
Heat/Cool Control used for both heating and cooling
(requires two control outputs).
Heat
Control used for heating.
Hysteresis When, at a precise moment, the value of
the controlled quantity depends not only on
another reference quantity but also on the
values that the controlled quantity had pre-
viously, there is hysteresis. Hysteresis can
therefore be considered inertia that influen-
ces the control system, causing variable
delays between the change of the reference
quantity and the change of the controlled
quantity.
ON-OFF Control procedure based on activation and
deactivation of the output. For heating, the
output stays on until PV is less than SV by
a certain quantity (offset), and then stays off
until PV is not greater than SV by the same
quantity (or different quantity, depending on
controller configuration). For cooling, the
output stays on until PV > SV - offset and
stays off until PV < SV + offset. This type of
control is not intelligent, does not consider
noise, and is not very accurate, but ensu-
res a limited number of switchings of the
output.
80209C_MHW_850-1650-1850_20-2020_ENG_pag. 8
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
www.gefran.com.
Overshoot Situation in which PV exceeds SV because
the control action stopped too late. The ON
OFF controls have an overshoot greater
than the PID controls.
PID Acronym for Proportional-Integration-Dif-
ferentiation, indicating a system with nega-
tive feedback, i.e., a device that acquires
a value from a process in input, compares
it to a reference value, and uses the diffe-
rence (error) to calculate the value of the
controller output variable, which is the va-
riable that controls the process. The output
is controlled based on the current value of
the error (proportional action), on a set of
previous error values (integral action), and
on the speed of change of the error value
(derivative action).
Pt100 A commonly used temperature measure-
ment device. At 0°C its resistance is 100
ohm, and at room temperature about 106
ohm. The Pt100 can be tested for galvanic
continuity and normal extension cables can
be used.
PV
Acronym for Process Value, i.e., the value
that the process variable (temperature, val-
ve opening, etc.) has at that moment.
Solid state
Also known as SSR, this is a relay designed
relay specifically for frequent switching. It has no
moving parts or mechanical contacts, but
may still break or short circuit. This type of
relay is often used in temperature control
systems such as PID.
Sensor Device that translates physical phenome-
na (such as change in resistance based on
temperature) into electrical signals that can
be acquired and processed by the control-
ler.
Setpoint Set value (see SV).