Delta RMC101 - Manual (Page 836)

RMC100 and RMCWin User Manual
C-66
C.5.6 Pressure/Force Scale and Offset Calculation Examples
Example 1
Suppose a pressure transducer gives an output from 0 to 10 volts. This range is represented by
Counts A from 0 to 32500. Also suppose that the range of pressures which will be used are from
0 psi to 2000 psi, and 0 psi gave a reading of 12 counts and 2000 psi gave a reading of 32522
counts.
Since the scale is less than 16383.5, use the Prescale Divisor bits in the Configuration Word to
divide the transducer counts by 8. Then multiply the scale by 8 to obtain:
This gives us an effective scale of 16127/8 or 2015.875, which is closer than we would have been
if we did not use the Prescale Divisor and instead used a scale of 2016.
An alternative way of doing this without actually measuring the pressure independently is to trust
the gauge. That is, assume that 0 psi will give 0 counts, and 2000 psi will give 32,500 counts.
Using these numbers, we get the following equation:
Again, we will apply a Prescale Divisor of 8 to obtain:
Next, we must calculate the offset. We use the following equation:
Therefore, by using the first point (0 psi at 0 counts or 0mV) and the second method
of calculating the scale, we get the following:
As you can see, the offset for gauges that give 0 volts at 0 pressure units will always have 0 for
an offset.