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I. Data Interpretation
The MS3500E supplies corrosion data in several formats:
• Probe Reading (‘Probe Life Units’)
• Metal Loss
• Corrosion Rate
• 4-20 mA (MS3510E)
1. Probe Reading
This information is available through the “MEASURE PROBE” (see p. 13) menu for current reading,
and through the “VIEW STORED DATA” (see p. 14) for historical readings. The probe reading,
commonly known as ‘probe life units’ (PLU), is an integer between 0-1000 and represents the percent-
age of the effective probe element thickness consumed since the probe was inserted into the corrosive
system. This value is most commonly used to calculate metal loss and/or corrosion rate, as shown
below:
ML =
..............................................(1)
CR =
........................(2)
ML = METAL LOSS IN MILS
X
= INSTRUMENT READING AT ANY GIVEN TIME
X
2
= INSTRUMENT READING AT TIME t
2
X
1
= INSTRUMENT READING AT TIME t
1
T
= TIME LAPSE (DAYS) BETWEEN READINGS X
1
AND X
2
CR = CORROSION RATE IN MILS PER YEAR
K
= PROBE CONSTANT
Table 1 gives probe constants for most common probe element geometries:
X x K
1000
(X
2
- X
1
) x K x 365
1000 x T