Delta RMC151 - Manual (Page 36)

RMC70/150 and RMCTools User Manual
Method 2: P0/P1 Calculation
The accuracy of this method depends on how accurately you can measure the pressure of
the axis.
1. Physically measure two different pressures of the axis and record the value of the
Voltage register at each point. (The difference between the two pressure should be as
large as possible). Call the smaller measured pressure P
0
, and its corresponding
Voltage V
0
. Call the greater measured pressure P
1
, and its corresponding Voltage V
1
.
2. Calculate the Pressure Scale with the following equation:
Pressure Scale = (P
0
-P
1
)/(V
0
-V
1
)
If the Pressure Scale is negative, ignore the minus sign. RMCTools accepts only a
positive Scale.
3. Calculate the Pressure Offset with the following equation:
Pressure Offset = P
0
- Pressure Scale x V
0
Scaling Dual-Input (Differential) Force
Dual-Input Force requires two pressure transducers. Each pressure transducer must be
individually scaled. The RMC calculates the Actual Differential Force every control-loop
using the following formulas:
Actual Force A = (Channel A Voltage (or Current) x Force A Scale) + Force A Offset
Actual Force B = (Channel B Voltage (or Current) x Force B Scale) + Force B Offset
Actual Differential Force = Actual Force A - Actual Force B
To correctly scale the axis for your particular application, use the method below to find the
A and B Force Scale and Force Offset parameters.
Method: Use Transducer Specifications
This method assumes the two pressure transducers or load cells provide zero volts at zero
pressure or force.
• From the transducer data sheet, find the maximum output voltage of your pressure
transducer and the pressure at that voltage.
• Calculate the area of the A side (cap end) of the piston.
• Multiply the area of the A side with the maximum pressure of the A transducer to get
the maximum A force.
• Calculate the Force A Scale with the following formula:
Force A Scale = maximum A force / Max A Voltage
• Calculate the effective area of the B side (rod end) of the piston. This is the area of the
cylinder minus the area of the rod.
• Multiply the area of the B side with the maximum pressure of the B transducer to get
the maximum B force.
• Calculate the Force B Scale with the following formula:
Force B Scale = maximum B force / Max B Voltage
• Make sure the system has 0 force and then record the value of the Channel A
Actual Force (to find this register, in Axis Status Registers pane, click the All tab,
and expand the Pressure/Force Feedback section). Negate the value and enter it
as the Force A Offset.
2.2.6. MDT Scaling
16 Delta Computer Systems, Inc.