Rosemount 3095FB - Appendix D: Scaled Integer Examples

Model 3095FB Multivariable Transmitter with Modbus Protocol
Modbus Protocol Guide
Page 78 of 79
Appendix D: Scaled Integer Examples
Example 1: Configure DP for -250 to 250 inches of water at 60 F with a scaled
integer range of 0 to 65,534
Method 1:
1. Configure the Scaled Integer Method for Method 1
2. Write a 0 to register DP_y1 (see Table 5-7)
3. Write a 65,534 to register DP_y2 (see Table 5-7)
4. Write a -250 to register DP_x1 (see Table 5-8)
5. Write a 250 to register DP_x2 (see Table 5-8)
Method 2:
1. Configure the Scaled Integer Method for Method 2
2. The Scale Factor = (y
2
- y
1
)/(x
2
- x
1
) = (65534 - 0) / (250 - (-250)) = 131.068
Since the Scale Factor must be an integer, the Scale Factor = 131
3. The Offset = (Scale Factor * x
1
) - y
1
+ 32768 = (131 * (-250)) - 0 +32768 = 18
4. Write a 65,534 to register Maximum Integer (see Table 5-9)
5. Write a 131 to register DP Scale Factor (see Table 5-10)
6. Write a 18 to register DP Offset (see Table 5-10)
Due to the conversion of the scale factor to an integer value, the actual limits are:
7. x
1
= (y
1
+ (Offset - 32768)) / Scale Factor = (0 + (18 - 32768)) / 131 = -250.0
8. x
2
= (y
2
+ (Offset - 32768)) / Scale Factor = (65534 + (18 - 32768)) / 131 = 250.26