Model 370 pH Sensor
13.5 EuroSenz
™
Instruction Sheet
PN 51A-370/rev.B
January 2011
SPECIFICATIONS
pH Range: 0-14 pH
Membrane Type: General Purpose (GPLR)
Percent Linearity: 97% @ 0-4 pH, 99% @ 4-12 pH,
96% @ 12-13 pH, 92% @ 13-14 pH
Wetted Materials: Glass, EPDM
Process Connection: Standard PG 13.5 Thread
Electrode Connection: Single Pole Euro Connector
Temperature Range: 0° - 100°C (32° - 212°F)
Pressure Range: 100 - 790 kPa abs (0 - 100 psig)
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 2.
For wiring, see Figures 3 and 4.
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.
Specifications subject to change without notice.
For additional information,
please visit our website at
www.emersonprocess.com/raihome/liquid/.
FIGURE 1. Sensor Dimensions
INCH
MILLIMETER
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
CAUTION
SENSOR/PROCESS APPLICATION COMPATIBILITY
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.
The wetted sensor materials may not be compatible
with process com position and operating conditions.
Application compatibility is entirely the
responsi-
bility of the user.
MAINTENANCE
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 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).
FIGURE 3. Wiring to Models 1181, 1054A/B, 2081, 54, 81, and 3081
1. INSTRUMENTS MUST BE USED IN MANUAL TEMPERATURE COMPENSATION MODE.
2. A SEPARATE THERMOCOUPLE MAY BE USED IF TEMPERATURE COMPENSATION IS DESIRED. PLEASE CONSULT APPROPRIATE ANALYZER/TRANSMITTER MANUAL FOR MORE WIRING DETAILS.
FOR USE WITH 1054 SERIES WITH INTEGRAL PREAMP IN ANALYZER, REQUIRES THE USE OF BNC ADAPTER (PN
9120516) TO BE PLACED ON THE BLACK WIRE.
WIRING SHOWN WITH PREAMP INTEGRAL TO THE MODEL 2081. IF USING REMOTE PREAMP IN JUNCTION BOX, THE
BLACK (mV IN) WILL GO TO TB1-2.
3
3
4
NOTE: NEWER CABLES MAY
HAVE DIFFERENT WIRE COLORS.
IN THIS CASE, THE BLACK WIRE
IS REFERENCE, AND THE
CLEAR/COPPER WIRE IS mV IN.
FIGURE 4. Wiring to Model 1055-10-22-32
Emerson Process Management
2400 Barranca Parkway
Irvine, CA 92606 USA
Tel: (949) 757-8500
Fax: (949) 474-7250
http://www.raihome.com
© Rosemount Analytical Inc. 2011
FIGURE 2. Sensor Orientation
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