Rosemount Manual: 399VP General Purpose pH/ORP Sensor Abridged | Rosemount Manuals & Guides
Model 399VP
General Purpose pH/ORP Sensor
Instruction Sheet
PN 51A-399VP/rev.J
January 2011
MODEL 399VP
Insertion/Submersion Sensor
with new VP8 connector
(uses mating VP8 cable)
CAUTION
The solution used during calibration is an acid and
should be handled with care. Follow the directions of
the acid manufacturer. Wear the proper protective
equipment. Do not let the solution come in contact
with skin or clothing. If contact with skin is made,
immediately rinse with clean water.
The wetted sensor materials may not be compatible
with process com position and operating conditions.
Application compat ibility is entirely the
responsi-
bility of the user.
CAUTION
SENSOR/PROCESS APPLICATION COMPATIBILITY
SPECIFICATIONS
Sensor Type: General purpose 399VP
Measured Range: pH: A
CCUGLASS 0-14
ORP: -1500 to +1500 mV
Percent Linearity Over pH Range:
Operating Temperature: 0° to 85°C (32° to 185°F)
Au tomatic temperature compensation 0° to 85°C (32°
to 185°F), Temperature compensation is not required for
399 ORP when used with Models 1060, or 1181 ORP
Maximum Pressure: 790 kPa [abs] (100 psig) at 65°C (see
Graph 1 below)
Flow Rate: up to 2 ft/sec
Materials of Construction: Tefzel, glass, ceramic, & Viton
Materials of ORP: Platinum
Process Connections: 1 in. MNPT, 2 places
VP8 Cable: use PN 24281-00
Weight/Shipping Weight: 0.45 kg/0.9 kg (1 lb/2 lb)
• High pH glass provides greater accuracy over 12.5 pH
• HF glass provides improved resistance to hydrofluoric acid up to
300 ppm
GPLR Hemi Bulb Flat Bulb
1-2 pH 94% 93%
2-12 pH 99% 98%
12-13 pH 97% 95%
13-14 pH 92% –
For additional information, please visit our website at
www.emersonprocess.com/raihome/liquid/.
ATEX DIRECTIVE
Special Conditions for safe use
1. All pH/ORP sensors have a plastic enclosure
which must only be cleaned with a damp cloth to
avoid the danger due to a build up of an electrostatic charge.
2. All pH/ORP sensor Models are intended to be in
contact with the process fluid and may not meet
the 500V r.m.s. a.c. test to earth. This must be
taken into consideration at installation.
WARNING
Before removing the sensor, be absolutely certain
that the process pressure is reduced to 0 psig and
the process temperature is lowered to a safe level!
2
STORAGE
1. It is recommended that electrodes be stored in their
original shipping containers until needed.
2. Do not store at temperatures below -5°C (23°F).
3. Electrodes should be stored with a protective cap
containing KCl solution (PN 9210342).
4. For overnight storage, immerse the sensor in tap
water or 4 pH buffer solution.
5. A pH glass electrode has a limited shelf life of one
year.
ELECTRODE PREPARATION
1. Remove electrode from shipping container.
2. Remove the protective boot covering the electrode
bulb.
3. Rinse away salt film with clean water, then shake
the electrode so that the internal solution fills the
bulb, thus removing any air trapped there.
NOTE
Do not allow lubricant to coat electrode bulb or
reference junction. If it does, wipe it clean before
installation.
INSTALLATION
For sensor orientation, see Figure 1.
For sensor dimensions, see Figure 2.
For wiring, see Figure 3 - 40.
TWO POINT BUFFER CALIBRATION
Select two stable buffer solutions, preferably pH 4.0
and 10.0 (pH buffers other than pH 4.0 and pH 10.0 can
be used as long as the pH values are at least two pH
units apart).
NOTE
A pH 7 buffer solution reads a mV value of
approx. zero, and pH buffers read approximately
± 59.1 mV for each pH unit above or below pH 7.
Check the pH buffer manufacturer specifications
for millivolt values at various temperatures since
it may affect the actual value of the buffer
solution mV/pH value.
1. Immerse sensor in the first buffer solution. Allow
sensor to equilibrate to the buffer temperature (to
avoid errors due to temperature differences
between the buffer solution and sensor temperature) and wait for reading to stabilize. Value of buffer
can now be acknowledged by analyzer/ transmitter.
2. Once the first buffer has been acknowledged by the
analyzer/transmitter, rinse the buffer solution off of
the sensor with distilled or deionized water.
3. Repeat steps 1 and 2 using the second buffer
solution.
4. The theoretical slope value, according to the Nernst
equation for calculating pH, is approximately 59.17
mV/pH. Over time the sensor will age, both in the
process and in storage, and will result in reduced
slope values. To ensure accurate readings, it is
recommended that the electrode be replaced when
the slope value falls below 47 to 49 mV/pH.
RECOMMENDED pH SENSOR
STANDARDIZATION
For maximum accuracy, the sensor can be standardized on-line or with a process grab sample after a buffer
calibration has been performed and the sensor has
been conditioned to the process. Standardization
accounts for the sensor junction potential and other
interferences. Standardization will not change the
sensor’s slope but will simply adjust the analyzer’s
reading to match that of the known process pH.
MAINTENANCE FOR pH ELECTRODE
Electrodes should respond rapidly. Sluggishness,
offsets, and erratic readings are indicators that the
electrodes may need cleaning or replacement.
1. To remove oil deposit, clean the electrode with a
mild non-abrasive detergent.
2. To remove scale deposits, soak electrodes for 30 to
60 minutes in a 5% hydrochloric acid solution.
3. Temperature effect on life expectancy: If glass
electrode life expectancy is 100% @ 25°C (77°F),
then it will be approximately 25% @ 80°C (176°F),
and approximately 5% @ 120°C (248°F).
MODEL 399VP INSTALLATION
3
MODEL 399VP INSTALLATION
FIGURE 2. Sensor Dimensions
DWG. NO. REV.
40399VP01 A
INCH
MILLIMETER
INSTALLATION
FIGURE 1. Sensor Orientation
MODEL 399VP INSTALLATION
4
ORP CALIBRATION
1. After making an electrical connection between the
sensor and the instrument, obtain a standard
solution of saturated quinhydrone (PN R508-8OZ).
This can also be made quite simply by adding a
few crystals of quinhydrone to either pH 4 or pH 7
buffer. Quinhydrone is only slightly soluble, therefore only a few crystals will be required.
2. Immerse the sensor in the standard solution. Allow
1-2 minutes for the ORP sensor to stabilize.
3. Adjust the standardize control of the instrument to
the solution value shown in the table below. The
resulting potentials, measured with a clean platinum electrode and saturated KCl/AgCl reference
electrode, should be within +/- 20 millivolts of the
value shown in the table below. Solution temperature
must be noted to ensure accurate interpretation of
results. The ORP value of saturated quinhydrone
solution is not stable over long periods of time.
Therefore, these standards should be made up
fresh each time they are used.
4. Remove the sensor from the buffer, rinse, and
install in the process.
MAINTENANCE FOR ORP ELECTRODE
Electrodes should respond rapidly. Sluggishness, offsets, and erratic readings are indicators that the electrodes may need cleaning or replacement.
1. To remove oil deposit, clean the electrode with a
mild non-abrasive detergent.
2. To remove scale deposits, soak electrodes for 30 to
60 minutes in a 5% hydrochloric acid solution.
3. ORP (metallic) electrodes should be polished with
moistened baking soda.
pH 4 Solution pH 7 Solution
Temp °C 20 25 30 20 25 30
mV Potential 268 264 260 94 87 80
ORP of Saturated Quinhydrone Solution (millivolts)
CAUTION
Hydrofluoric acid and the mixture of Hydrochloric
acid and thiourea is toxic and highly corrosive. Avoid
skin contact, wear protective gloves. Use only in a
well ventilated area. Do not inhale fumes. In case of
an accident, consult a doctor immediately.
FIGURE 5. VP8 Cable, instrument end
FIGURE 4. VP8 Cable, sensor end
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