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FM terminal
Terminal function
This terminal is used for connecting an analog voltmeter or a digital frequency meter and thus to monitor and
display output frequency. Alternatively, motor current can be monitored instead (when output current is
selected the FM terminal can only supply an analog signal).
1) Frequency display using analog output signal
The analog output signal is a pulse train whose period remains constant. The width of the pulses ist
proportional to the actual output frequency (0 to 10V represent 0Hz to maximum frequency):
Adjustment of this signal is done using function b 81. The signal accuracy following adjustment is
+/-5%
2) Frequency display using digital output signal
The frequency of this signal is proportional to the output frequency. The duty cycle is approximately
50%:
The signal frequency equals the actual output frequency multiplied by the factor configured under b 86.
3) Motor current display using analog output signal
This signal is identical to the one described under 1). The width of the pulses is proportional to the actual
motor current. The maximum voltage of 10V is reached when the motor current is two times the inverter
rated current. The signal accuracy is +/-20%. The connection to a meter is described under 1). A moving
iron type amperemeter should be used.
Configuration
C 23 b 81 b 86
1) In order to select analog frequency, digital frequency, or analog motor current, use function C 23.
2) When an analog output signal is used (frequency or current), the signal can be adjusted to the special
meter used by specifying a factor under b 81.
3) When the digital output signal (frequency only) is selected, the output signal can be adjusted to the
special meter used by specifying a factor under b 86.
T
0 to 10V
1mA
f
T
Digital fre-
T = 1/(output frequency*factor)
quency meter
Example of a terminal
connection using
33k
a low pass filter:
1µF
7-3
Chapter 7 – Control circuit terminal functions
t
10V
t
=variable
T
T=4ms (constant)
10V
82k
U
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