Rockwell Automation 1771-SF1 SERVO INT MOD - Manual (Page 14)

Programming and Operation
Chapter 3
3Ć2
lower 11 bits to the 0 to 10V DC analog output. Bit 12 designates the sign
+ or - for forward or reverse motion. The resolution of the
digital-to-analog conversion is +10V/2048 bits or approximately
4.883 mV/bit.
Table 3.A shows the relationship between the input binary number from
the micro controller and the analog output voltage from the servo
interface module for sample values. The binary number for any desired
output voltage can be determined as follows:
POSITIVE OUTPUT
1. Output voltage (volts) ” decimal equivalent of the binary number.
4.883 x 10 -3 (volts/bit)
2. Convert the decimal equivalent to the binary number.
3. Take the complement of the binary number.
NEGATIVE OUTPUT
1. Output Voltage (volts) ” decimal equivalent of the binary number.
4.883 x 10
-3
(volts/bit)
2. Convert the decimal equivalent to the binary number.
3. Add 1 bit to the binary number.
Refer to the rpm/voltage chart provided by the servo motor manufacturer
to complete the relationship between the DAC input binary number and
servo motor speed and to determine the direction of rotation which is
indicated by the sign bit.