Delta RMC101 - Manual (Page 553)

Analog 6.1
Transducer Interface Modules 6-9
Translating to Speed Units
The Scale, Offset, and the Prescale Divisor bits of the Configuration word parameters are used to
define velocity units as a function of transducer counts.
The following formula summarizes the translation from transducer counts to Actual Speed units
for velocity control or velocity reference axes:
The Actual Speed calculation does not use the Offset parameter. To add an offset for the Actual
Speed, see the Set Count Offset Command topic.
The Offset parameter is used in calculating the Actual Position from the Actual Speed. However,
the Actual Position for a velocity axis is typically not important, and for axes with an analog
velocity input, it is typically not very accurate.
Translating to Position Units
The Scale, Offset, and the Prescale Divisor bits of the Configuration word parameters are used to
define position units as a function of transducer counts.
The following formula summarizes the translation from transducer counts to Actual Position units:
If the Actual Position overflows the valid 16-bit position range, as described above, the Position
Overflow bit will turn on, forcing the axis to halt.
To calculate these parameters, you must physically measure the axis’s position at two points and
read how many counts the RMC reports at each position. If we call the two positions, in user
position units, P0 and P1, and call the corresponding counts C0 and C1, the following two
equations will give a Scale and Offset. Notice that the Prescale Divisor is left out at this point; it is
assumed to be 1:
Once the Scale is calculated, the Prescale Divisor can be calculated. The Prescale Divisor can
have values of 1, 2, 4, or 8. Because the Scale is always divided by the Prescale Divisor, you
essentially have a fractional scale. Pick the largest Prescale Divisor you can multiply the Scale by
and still be between 32767 and 32767. For example, suppose your Scale comes to 6324.70. The
following table shows the possible Scales and Prescale Divisors you could use and the effective