Rosemount 396P And 396Pvp Orp Sensors - Emerson Rosemount 396PVP Instruction Manual

Section 5: Maintenance
March 2017
NOTE: Erroneous pH results may result immedi ately after acid soak, due to reference junction
potential build-up. Replace the sensor if cleaning does not restore sensor operation.
TABLE 5-1. Ro and R1 Values for Temperature Compensation Elements
Temperature
Compensation Element
TABLE 5-2. Temperature vs Resistance of Auto T.C. Elements
Temperature °C
5.4 Rosemount 396P and 396PVP ORP
5.4.1 Platinum Electrode Check
The platinum electrode may be checked as follows: There are two types of standard solutions
which may be used to check the ORP electrode/transmitter system.
Type 1: One type of commonly used ORP standard solution is the saturated quinhydrone solu-
tion. Refer to Section 5.2.
CAUTION
The solution used during the following check is an acid and should be handled with care. Follow the
directions of the acid manufacturer. Wear the proper protective equipment. If contact with skin of
clothing is made, immediately rinse with plenty of clean water.
Type 2: A second ORP standard solution is the Ferric-Ferrous Ammonium Sulfate Solution (PN
R508-16OZ), and it can be ordered as a spare part; otherwise, it can be prepared from the
following recipe: Dissolve 39.2 grams of reagent grade ferrous ammonium sulfate, Fe(NH4)2
(SO4)2 • 6H2O and 48.2 grams of reagent grade ferric ammonium sulfate, FeNH4(SO4)2 •
12H2O, in approximately 700 milliliters of water (distilled water is preferred, but tap water is
acceptable). Slowly and carefully add 56.2 milliliters of concentrated sulfuric acid. Add suffi-
cient water to bring the total solution volume up to 1000 ml. This standard ORP solution,
although not as simple to prepare as the quinhydrone recipe, is much more stable, and will
maintain its millivolt value for approximately one year when stored in glass containers. This
38
R
o
3K 2934
Pt100 107.7
Resistance (Ohms) ±1%
3K
0 2670
10 2802
20 2934
25 3000
30 3066
40 3198
50 3330
60 3462
70 3594
80 3726
90 3858
100 3990
R
1
.0045
.00385
Pt100
100.0
103.8
107.7
109.6
111.5
115.4
119.2
123.1
126.9
130.8
134.6
138.5
Instruction Manual
LIQ-MAN-396P-396PVP
Maintenance