Emerson instruction manual 396P and 396PVP ORP, Maintenance

Section 5: Maintenance	396P + 396PVP Sensors Instruction Manual
August 2013	LIQ_MAN_396P_396PVP

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	Ro	R1
Compensation Element
3K	2934	.0045
Pt100	107.7	.00385

TABLE 5-2. Temperature vs Resistance of Auto T.C. Elements

Temperature °C	Resistance (Ohms) ±1%
	3K	Pt100
0	2670	100.0
10	2802	103.8
20	2934	107.7
25	3000	109.6
30	3066	111.5
40	3198	115.4
50	3330	119.2
60	3462	123.1
70	3594	126.9
80	3726	130.8
90	3858	134.6
100	3990	138.5

5.4396P and 396PVP ORP

5.4.1Platinum 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 sufficient 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 milli- volt value for approximately one year when stored in glass containers. This solution (ferric/ferrous

38 Maintenance