Elcometer SCM400 Operating Instructions Manual page 13

If the exact make-up of the contaminant is known, calibration curves shown in
Figure 4 can be produced with solutions of known concentration. These can be
used to interpret readings more accurately.
20
18
16
14
12
10
8
6
4
2
0
2
Figure 4. Readings obtained with Different Salts
Temperature could affect readings taken. The Elcometer 130 SCM400 has
been calibrated with sodium chloride at 25° C. Figur e 5 illustrates the small
variation that might be expected in the range 15° C to 35°C. In most cases it is
likely that this variation will not be significant. However, the temperature can be
corrected by using the graphs given in Figure 5 and as detailed in "Technical
specification" on page 19.
The proportion of the soluble salt present on the surface being tested which is
removed by the sample paper will also affect readings. This factor is common
to all surface sampling methods. Tests have shown that removal rates are as
follows:-
Smooth machined surfaces:
Grit blasted steel (to Swedish Standard
Sa3) with a surface profile of 100 µm:
For coarser surface finishes:
4 6 8 10 12
ACTUAL SALT LEVEL
(µg cm -2 )
(All Measurements taken at 25° C)
SODIUM CHLORIDE
MARINE CONTAMINATION
URBAN CONTAMINATION
14 16 18 20
>95%
>85%
70% (approximately)
11