Delta RMC101 - Manual (Page 837)

Appendix C: Parameter Field Reference
C-67
Example 2
Suppose a pressure transducer gives an output from 4 to 20mA. This range is represented by
Counts from 6500 to 32500. Also suppose that the range of pressures which will be used are
from 0 to 10 bars, and 0.0 bars read 6487 counts and 10.0 bars read 32662 counts. We must
choose our position units first. It is not a good idea to just use bars, as the user will only be able
to see 0 to 10 bars and no fractions. Therefore, it makes more sense to use millibars as position
units and go from 0 to 10,000 millibars. The scale calculation goes as follows:
Again, since the scale is less than 16383.5, use the Prescale Divisor bits in the Configuration
Word to divide the transducer counts by 2. Then multiply the scale by 2 to obtain:
Assuming we cannot or do not want to verify the gauge’s accuracy, we can use the specified
gauge requirements. Therefore, we assume that 0.0 bars reads 6500 counts, and 10.0 bars reads
32500 counts. Using these numbers, we get the following equation:
Again, we will apply a Prescale Divisor of 2 to obtain:
Next, we must calculate the offset. We use the following equation:
Therefore, by using the first point (0 psi at 6500 counts or 4mA) and the second
method of calculating the scale, we get the following:
Example 3
Suppose we want to control differential force. We use the same gauges on both the A and B
sides of the cylinder. These gauges are rated to have 4mA at 0 psi and 20mA at 7500 psi.
Therefore, each channel will have 6500 counts at 0 psi and 32500 counts at 7500 psi. The
cylinder has an internal diameter of 6 inches. The rod has an outside diameter of 2 inches.
Therefore we find the maximum force applied on each end:
Force = Pressure x Area