Allen-Bradley 871TM-M**NP12 Series, User Manual, Page: 11 / 90

Rockwell Automation Publication 871TM-UM002C-EN-P - October 2017 11
Product Overview Chapter 1
Correction Factors
To determine the sensing distance for materials other than the standard mild
steel, a correction factor is used. The correction factors are used as a general
guideline for determining the de-rated sensing distance, if applicable.
Instructions for unshielded sensor: To determine the appropriate correction
factor, use Table 1. Multiply the sensor type with the target material by the
sensing range to determine de-rated sensing distance, if applicable.
Instructions for shielded sensor: To determine the appropriate correction
factor, use Table 1 and Table 2 . In Table 1 , determine the appropriate
correction factor based on the type and the target material. Then, in Table 2 ,
multiply the result from Table 1 by the material the sensor is mounted in. This
number is the final correction factor.
Table 1
Table 2
The following table indicates the protrusion distance from the mounting
device for the unshielded sensor face.
Target Material
(No Surrounding
Metal)
Barrel Size and Nominal Sensing Range
M12 M18 M30
6 mm (Shielded) 10 mm (Unshielded) 10 mm (Shielded) 20 mm (Unshielded) 20 mm (Shielded) 40 mm (Unshielded)
Steel
1 1 1 1 1 1
Copper
0.85 0.8 0.8 0.9 0.9 0.9
Aluminum
1 1 1 1 1 1
Brass
1.3 1.4 1.2 1.35 1.3 1.2
Stainless Steel
1 mm/2 mm thick
0.5/0.9
(1)
/0.65 0.5/0.9 0.2/0.7 0.35/0.7
(1)
/0.25
(1) No detection.
Surrounding Material Type 8 mm Dia., Shielded 12 mm Dia., Shielded 18 mm Dia., Shielded 30 mm Dia., Shielded
Steel
1 0.7 0.75 0.9
Aluminum
0.9 1.15 0.9 0.7
Brass
0.9 1.05 0.75 0.6
Stainless Steel
1 0.8 0.8 1.3
Unshielded Sensor Distance
from Mounting Device [mm (in.)]
8 mm Dia. 12 mm Dia. 18 mm Dia. 30 mm Dia.
Unshielded
Steel 15 (0.59) 22 (0.87) 36 (1.41) 18 (0.71)
Aluminum 9 (0.35) 13 (0.51) 22 (0.87) 34 (1.34)
Brass 10 (0.39) 15 (0.59) 22 (0.87) 34 (1.34)
Stainless Steel 14 (0.55) 21 (0.83) 43 (1.69) 18 (0.71)
See table