User manual - RATEMETER STI-73
6.
PRINCIPLE OF OPERATION
After turning the power supply on, device ID and software version are showed on the
display, next the controller goes to the measurement mode.
6.1.
MEASUREMENT MODE
In the measurement mode the device shows current measurement value (
rotational
speed or time per one revolution
, it depends on
“F or P”
parameter) with resolution defined by
“PrEc”
parameter (max 5 digits after decimal point).
Pulses delivered to the input (Figure 4.9) are converted in manner described below:
•
If duration of LOW or HIGH state is lower than time defined by parameter
“FrEq”
(see
Tab.7.2 on page 28), pulses are interpreted as disturbances and ignored.
•
If duration of both states is in the defined range, but their frequency is lower than value of
“FrEq”
parameter, the device goes to alarm state - relays and current output (if mounted)
are switched to their alarm states (defined by their
“ALArmS”
parameters). In this state
message
"-Hi-"
is displayed instead of measurement value.
•
In other cases (during frequency and duration of the signal are in permitted ranges) pulses
are delivered to internal frequency divider. The divider (see description of parameter
“PULSEn”
) should be set to value equal the number of pulses per revolution – in such
case one pulse goes out of the divider every revolution, and it allows to minimize errors
caused by roughness of measurement element (e.g. rack if inductive detector is used).
The frequency after the divider is recalculated according to selected by user measurement
unit (parameter
“unit”
), and can be expressed by rev./sec , rev./min or rev./h. Final value
is obtained by multiplication the measurement result by parameter
“mul”,
and division by
parameter
“div”
. Parameters
“mul”
and
“div”
allow to free scaling of the measurement,
and obtain automatic recalculation of rotational speed to linear speed (see example on
page 32). Obtained result is displayed during measurement mode, and is the base of
relays and current output states calculation, and is accessible via RS-485 interface with
MODBUS protocol.
–
If input frequency is in the permitted range but calculated value can not be fitted
on 6 digits, message
“-Ov-”
is displayed instead of the result.
(modify parameters
“unit”, “PrEc”, “mul”
and
“div”,
to fit the result on 6 digits).
–
While
time per one revolution is displayed
(parameter
“F or P”
=
“PEriod”):
•
If input frequency equals 0, then message
“-StoP-”
is displayed.
•
If value of period is to high to be fitted on 6 digits, message
“-OvLd-”
(Overload) is displayed instead of the result.
•
If input frequency is different than 0 but value of period is to small to be
fitted on 6 digits, message
“-UnLd-”
(Underload) is displayed instead of
the result.
In the measurement mode user can check main thresholds values. After pressing
[^]
or
[v]
button, name of the threshold (e.g.
”rELPr1”
) and his value will be displayed on the
display in alternating mode. If
[^]
or
[v]
will be pressed in 5 sec again, the next threshold will
be displayed, else the device comes back to the measurement mode. If a
free access
is
enabled (see description of
”SECu” menu
), user can change the value of particular threshold
pressing button
[ENTER]
(see:
PARAMETERS EDITION
).
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