User manual

FRONT PANEL ADJUSTMENT TRIMPOTS
REF. GAIN : Attenuates the output of the reference signal gain differential amplifier.
Fully CW will send the full reference signal to the servo preamplifier stage. CCW
rotation will result in less reference signal sent to the preamp. This adjustment acts
like an overall ‘volume’ control for the amplifier, controlling the amps-out per volt-in.
TACH. GAIN : Adjusts the tachometer scaling signal. When fully CW, a 10V
reference signal will demand 10V from the tachometer. As this is adjusted CCW, the
motor speed will increase. Use this to set the basic RPM-out to volts-in ratio of the
amplifier.
FEEDBACK : Sets the gain of the servo preamplifier. Usually set to a minimum (
fully CW ) in current mode operation for maximum bandwidth. When using
tachometers, turn this pot CCW until oscillation begins, and then back off 1 or 2
turns for stable operation. Adjustment of this pot affects the response of the amplifier
to a step input.
BALANCE : Used to ‘null’ the output of the amplifier when the reference inputs are
at 0 V. adjust the pot for zero current, or for zero volts between motor + and motor-
when the input to the amplifier is zero.
PEAK CURRENT LIMIT : Controls the peak current the amplifier can output to the
load. Fully CW the amplifier will drive the rated peak current. As this is turned CCW,
the maximum current will gradually decrease. Useful for protecting mechanical parts
when the maximum current required by the load is less than the amplifier’s peak
rating.
CONTINUOUS CURRENT LIMIT : Controls the continuous current that the
amplifier can output to the load. Fully CW the amplifier will drive the rated
continuous current. As this is turned CCW, the continuous current will gradually
decrease. Useful for protecting motors such as printed-circuit and basket-wound
motors that have high peak current but low continuous current ratings.
IR COMPENSATION : Used in voltage feedback mode with S3 and S7 on. Adjusts
the amount of positive feedback from the current circuit. This feedback increases the
output voltage when the load draws a higher current. Because it is positive feedback,
too much of it can cause severe oscillation. When adjusted correctly the motor speed
will remain constant as the load changes, without using a tachometer.