Rosemount Analytical 3900 Operating Manual

Model 3900/3900VP

General Purpose pH/ORP Sensor

For additional information, please visit our website at

www.emersonprocess.com/raihome/liquid/.

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.

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!

WARNING

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 3900
Measured Range: pH: A

CCUGLASS 0-14

ORP: -1500 to +1500 mV

Percent Linearity Over pH Range:

Operating Temperature: -10° to 100°C (14° to 212°F)

Automatic temperature compensation -10° to 100°C
(14° to 212°F)

Maximum Pressure: 790 kPa [abs] (100 psig) at 100°C

(212°F)

Materials of Construction: stainless steel, glass, Teflon,

polyphenylene sulfide (PPS), and EPDM

Materials of ORP: Platinum
Process Connections

Front facing:

3

⁄4˝ and 1˝ MNPT

Rear facing: 1˝ MNPT

Integral Cable: 32 ft (10m) cable with integral SMART pre-

amp; 15 ft (4.7m) cable without preamp sensor

VP8 Cable: use 24281-XX, 2.5 ft (.8m) to 100 ft (31m)
Weight/Shipping Weight: 0.45 kg/0.9 kg (1 lb/2 lb)

Instruction Sheet

PN 51A-3900
September 2010/rev.A

MODEL 3900

Insertion/Submersion

Sensor

Range Linearity

0 - 7 97%

1 - 7 98%

4 - 7 98%

7 - 10 99%

7 - 12 97%

7 - 13 96%

7 - 14 95%

2

STORAGE

1. It is recommended that electrodes be stored in their
original shipping containers until needed.

2. Do not store at temperatures below -10°C (14°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.

INSTALLATION

For sensor orientation, see Figure 1.

For sensor dimensions, see Figure 2.

For mounting options, see Figures 3-6.

For wiring, see Figures 7-22.

For additional wiring information, please visit our website
at www.emersonprocess.com/raihome/liquid/wiring.

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 59.1
mV/pH. Over time the sensor will age, both in the
process and in storage, which 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 1 to 5
minutes in a 5% hydrochloric acid solution.

3. Temperature effect on life expectancy: If glass
electrode life expectancy is 100% at 25°C (77°F),
then it will be approximately 25% at 80°C (176°F),
and approximately 10% at 100°C (212°F).

MODEL 3900 INSTALLATION

CAUTION

Hydrochloric acid 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.

3

ORP CALIBRATION

1. After making an electrical connection between the
sensor and the instrument, obtain a standard
solution of saturated quinhydrone PN R508-8OZ
(475mV). 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. Standardize the instrument to the solution value
shown in the table, right. 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 1 to

5 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)

MODEL 3900 INSTALLATION

FIGURE 1. Sensor Orientation

FIGURE 2. Sensor Dimensions

Model 3900

Model 3900VP

TEMP COMP

SOLN GND

REFERENCE

JUNCTION

pH ELECTRODE

3/4 IN MNPT

.92

1 IN MNPT

2.33

WRENCH FLATS

1.30 IN ACROSS

6.91

8.63

1 IN MNPT

4

psig (kPa [abs]) °F (°C)

150 (1136) 150 (65)

128 (984) 160 (71)

102 (805) 170 (77)

80 (653) 180 (82)

57 (494) 200 (93)

48 (432) 210 (99)

Horizontal Pipe Tee (PN 2002011)

Pressure/Temperature Ratings

MODEL 3900 INSTALLATION

FIGURE 3: Typical Flow Through insertion installation using PN 2002011 Pipe Tee

(sensor must be installed at least 10° above the horizon)

MILLIMETER

INCH

Inlet and outlet connections are stainless
steel and take 1/4-inch OD tubing. Flow cell
is polycarbonate with 1/4-inch FNPT fittings.

WETTED MATERIALS:

BODY - ACRYLIC

NUT - CPVC

FITTINGS - 316 SST

SEALS - BUNA N

FLOW CELL RATINGS

TEMPERATURE: 32˚-194˚F (0-90˚C)
MAX. PRESSURE: 90 PSIG (721 kPa [abs])
FLOW RATE: 2-5 GPH (7.6-18.9 LPH)

FIGURE 4: Low Flow Cell PN 24091-00

5

MODEL 3900 INSTALLATION

Jet Spray Cleaner shown with

Model 3900VP pH sensor

The Jet Spray Cleaner eliminates routine,
manual sensor maintenance by cleaning
the sensor with water or compressed air.
Flow through the cleaner can be controlled
by a solenoid valve.

NOTE: The Jet Spray Cleaner can be used with Handrail
Mounting Assembly (PN 11275-01, not shown) or can be
mounted through conduit as shown above.

FIGURE 5: Jet Spray Cleaner PN 12707-00

FIGURE 6. Submersion Installation

Using the Handrail Mounting

Assembly

(PN 11275-01)

All parts shown are supplied;

sensor is sold separately.

MILLIMETER

INCH