Measurement Computing DBK70 - Manual (Page 106)

B-2 Scale & Offset in Summary View 937696 Appendix B
Format for the Display of Received Data in an Output Channel Icon
The data displayed in an Output Channel Icon uses the same scaling process as is used to calculate the SRD
but with the PC Display Scale and PC Display Offset values instead of the Output Scale and Output Offset
values.
Data displayed in an Output Channel Icon is displayed as a signed 32 bit integer (i.e., -2 31 to +2 31 ).
Details for calculating PC Display Scale and PC Display Offset parameters are shown below.
Processing of SRD by Analog Output Channels
For analog output signals, the SRD is interpreted as a µVDC (i.e., 0.000001 VDC) value. The lowest signal
value above 0 is 1 µVDC (i.e., SRD = 1) and the highest signal value is 5,000,000 µVDC
(i.e., SRD = 5,000,000).
• If SRD < 0, then signal = 0 VDC (i.e., no signal)
• If SRD >/= 5,000,000, then signal = 5,000,000 µVDC (i.e., 5.000000 VDC)
• If 1
Calculating Scale and Offset
General Scale and Offset Calculations
To calculate the scale and offset field values used to create a scaled output signal or a displayed value from
the received data, the following formulas can be used.
Where: V
H
= Highest output channel value (e.g., 5,000,000 µ)
V
L
= Lowest output channel value (e.g., 0 µVDC)
D
H
= Highest scaled data value (e.g., 10,000 RPM)
D
L
= Lowest scaled data value (e.g., 0 RPM)
S
H
= Highest transmitted value
S
L
= Lowest transmitted value
R = Resolution = Scaled data value/bit of received data value (e.g., 0.25 RPM/bit)
Scale = [(V
H
- V
L
)/ (D
H
– D
L
)] * R
Offset = [(S
L
-D
L
)/(R)] * Output Scale
The following sections contain examples of calculating Output Scale and Offset values for analog output
signals, and calculating of PC Display Scale and Offset values.