Allen-Bradley 1391B Series, Instruction Manual

Page: 81 / 82

D Appendix
D-79
Controller Options
Zero Current Option (-A13) The Zero Current Option allows the user to externally adjust the current
limit of the controller from zero to 200% of the rated controller output.
Operation/Set-up
ATTENTION: To avoid a shock hazard, assure that all power
to the controller has been removed before connecting
potentiometer.
!
A user supplied, 10k ohm, 1/2 watt potentiometer must be connected as
shown in Figure D.1 (a 10-turn potentiometer is suggested for accuracy).
Attach a digital voltmeter between TP21 (+) and TP12 (–) of the controller.
For zero current, adjust the 10k potentiometer until a zero (
±
100 mV)
reading is achieved.
Alternately, a variable 7.5V DC voltage supply can be connected to
TB2-19 (+) and 20 (–). Varying the voltage at TB2-19 will modify the
current limit of the controller as set by selector switch S1 (this rating will
not exceed 200% of the controller current rating).
Zero volts will set the controller for zero current. 6V DC equals 200% and
7.5V DC provides 300% of the S1 setting.
Figure D.1
Option Connection
17.8k
+12V DC
TB2-19
TB2-18
TB2-20
1391B-ES Control Board
10k Ohm,
1/2 Watt
10-Turn Poten-
tiometer