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FEMA ELECTRÓNICA . SERIES B . Models Bxx-C1
1.13.9 Ratemeter and periodmeter modes description
The instrument offers 2 selectable ratemeter modes and 1
periodmeter mode. Ratemeters provide a reading propor-
tional to the frequency measured, while reading at period-
meters is proportional to the time between impulses
• Standard ratemeter ('rt.6') (see section 1.13.10) to read
speed values from impulse frequency signals.
• Quadrature ratemeter ('rtq.7') (see section 1.13.11) to
read speed values and the turning sense of the axis, from
two quadrature frequency signals, such as those pro-
vided by a bidirectional encoder. Speed is positive when
the quadrature turns clockwise and negative when turns
counterclockwise.
• Standard periodmeter ('Prd.8') (see section 1.13.12) to
read time between impulses. For applications with long
periods (long time between impulses) the 'SLOW' mode
offers the best possible response time for each applica-
tion.
All modes have scalable reading through multiplier (1 to
999999) and divider (1 to 999999) parameters, and a config-
urable time window ('GAtE') to adjust the measure refresh
time.
1.13.10 Ratemeter 'rt.6' configuration menu
Ratemeter
Multiplier
conf.
Divider
Time window
'SLOW' mode
Average filter
14
Multiplier
1 to 999999
Divider
1 to 999999
Seconds
Max. waiting time
Number of pulses
Filter strength
(0 = disabled)
• 'SLOW' mode
The 'SLOW' mode is an optional mode for very slow appli-
cations. Applies to ratemeter and periodmeter modes. The
'SLOW' mode accepts measures frequencies down to 1 mHz
(0,001 Hz or 1000 seconds between impulses), and is func-
tional up to 200 Hz.
The 'SLOW' mode offers the fastest response time for any
given application, calculating the frequency and period val-
ues each time a new impulse is received.
At the The 'Max. waiting time' parameter set a value be-
tween 1 and 1000 seconds. Select '0' to disable the 'SLOW'
mode. If time between impulses is higher than the configured
value, the instrument assumes that the signal has stopped
and forces the reading to '0' (both in ratemeters and peri-
odmeters). The 'GATE' parameter has no effect if the 'SLOW'
mode is active.
At the The 'Number of pulses' parameter set a value be-
tween 1 and 32. This paremeter defines the number of puls-
es that will be taken to calculate the period.
In 'Quadrature ratemeter' ('rtq.7') mode, the 'SLOW' mode
calculates the frequency between two consecutive impulses
received at channel 'A', and calculates the turning direction
by comparing impulses at channel 'A' with the state of chan-
nel 'B'. The 'Quadrature edges' parameter is fixed to '1--1'.
Application: to measure the speed of the propeller on ships,
using two inductive sensors in quadrature, at low revolu-
tions per minute.
Configuration menu for mode 'ratemeter' ('rt.6'). Mea-
sured frequency is multiplied by the value of the 'multiplier'
('MuLt') parameter and divided by the 'divider' ('dIV') pa-
rameter. Result is shown on the display. The measure is up-
dated on display as configured on the 'GAtE' parameter.
• set the 'Multiplier' ('MuLt') parameter from 1 to 999999.
• set the 'Divider' ('dIV') parameter from 1 to 999999.
• select the 'Time window' ('GAtE') parameter at 0.5, 1.0, 2.0,
4.0, 8.0 or 16.0 seconds. This parameter defines how often
the measure will be refreshed on display. This parameter
has no effect if 'SLOW' mode is active.
• for slow frequencies activate the 'SLoW' parameter con-
figuring the 'tIME' parameter between 1 and 1000 seconds.
See 1.13.9 for more information. Configure the 'nuMb' pa-
rameter between 1 and 32 impulses.
• if reading is unstable, set the 'Average filter' ('AVr') param-
eter to 'on' to activate a recursive filter on the display, and
configure the filter strength from 0.0 to 99.9. The filter is
stronger for higher values. Strong filters make readings more
stable and changes slower to update. Set '0' to disable the
filter.
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