Emerson Control Techniques Focus 3N, User Manual, Page: 51 / 82

Page 45
Optional Tuning Adjustments
The fo llowing adjustments are only required when either the current follower input (i.e.
4-20 mA input) or the voltage follower input (i.e. tachometer follower) is used. Only one
of these inputs may be used. Terminal #16 must be tied to +24 Vdc (terminal #1) to
activate the follower input speed command; typically this selection is made by the
Auto/Manual selector switch (see page 31) .
Signal Follower Zero Bias (BIAS) used with Voltage Input (TB2-18)
unwanted
offset
S) used with Current Input (TB2-17)
he BIAS pot prevents “creep” in the motor speed by eliminating any T
voltage levels in the voltage source. It may also be used to add a slight offset to
the voltage signal.
Signal Follower Zero Bias (BIA
Adjust the BIAS pot so the drive is at zero speed when the minimum current
signal follower speed command (4-20 or 1 –5 mA) is applied.
If a 4-20mA speed command is required, use the optional signal isolation
board (F3NSBD).
Voltage / Speed Signal Follower Gain (SP REF GAIN)
The SP REF GAIN pot calibrates the User supplied Voltage Signal Follower
peed command (0 - 200 Vdc s ) so the motor reaches its rated voltage/speed when the
its maximum value. It is factory preset to its full input voltage signal is set to
ounterclockwise position. c
Current Signal Follower Gain (IREF GAIN)
The IREF GAIN pot calibrates the User supplied Current Signal Follower speed
command ( 1-5mA or 4-20mA ) so the motor reaches its rated voltage/speed when the
current signal is set to its maximum value. It is factory preset to its full clockwise
position.