Vernier FPH-BTA User Manual

Tris-Compatible
Flat pH Sensor

(Order Code FPH-BTA)

The Tris-Compatible Flat pH Sensor
measures the pH of a solution or
semisol id. Because the glass membrane
is flat instead of a bulb, it is more
durable, easier to clean, and allows for flat surface measurements and smaller
sample sizes. It features a sealed, gel-filled, double-junction electrode, making it
compatible with Tris buffers and solutions containing proteins or sulfides. The
attached Electrode Amplifier stores a custom calibration.

Note: Vernier products are designed for educational use. Our products are not
designed nor are they recommended for any industrial, medical, or commercial
process such as life support, patient diagnosis, control of a manufacturing
process, or industrial testing of any kind.

What's Included

 pH Electrode
 Electrode Amplifier connected via BNC
 Electrode Storage Bottle, containing pH 4/KCl solution

Compatible Software and Interfaces

See www.vern ier.c om/man ua ls/f ph -bt a fo r a li st o f interfa ces and so ftw are c ompat ible
with the Tris-Compatible Flat pH Sensor.

Getting S tarted

1. Connect the sensor to the interface (LabQuest Mini, LabQuest 2, etc.).

2. Start the appropriate data-collection software (Logger Pro, Logger Lite,
LabQuest App) if not already running, and choose New from File menu.

The software will identify the sensor and load a default data-collection setup. You
are now ready to continue your experiment.

If you are collecting data using a Chromebook™, mobile device such as iPad

®

or
Android™ tablet, or a Vernier wireless sensor or interface, please see the following
link for up-to-date connection information:

www.vern ier. com/s tart /f ph-bt a

Using the Product

1. Remove the storage bottle from the electrode by unscrewing the lid and

removing the bottle and lid.

2. Thoroughly rinse the lower section of the probe, especially around the

bulb-shaped tip, using distilled or deionized water.

3. Connect the sensor following the steps in the Getting Started section of this

user manual.

4. When you are finished making measurements, rinse the electrode with distilled
water.

5. Slide the cap onto the electrode body and then screw the cap onto the storage
bottle so the tip of the electrode is immersed in the storage solution.

Important: Do not fully submerge the sensor. The handle is not waterproof.

Do not leave the electrode in acids or bases with concentrations greater than

1.0 M for periods longer than 5 minutes. See

www.vern ier. com/p h- sen sor s for oth er

types of pH electrodes.

Calibration

For many experiments, calibrating the Tris-Compatible Flat pH Sensor is not
required. A calibration equation is stored on each Tris-Compatible Flat pH Sensor
before it is shipped, which is used as a default by Vernier software.

For the most accurate measurements with this sensor, we recommend calibration. It
is a simple process that takes only a few minutes.

 For instructions for Tris-Compatible Flat pH Sensor calibration using

Logger Pro computer software, see

www.vern ier. com/t il/2341

 For instructions for Tris-Compatible Flat pH Sensor calibration using

LabQuest App, see

www.vern ier. com/t il/3394

 For instructions for Tris-Compatible Flat pH Sensor calibration using

Graphical Analysis with a Chromebook, see

www.vern ier. com/t il/3631

 For instructions for Tris-Compatible Flat pH Sensor calibration using

Graphical Analysis with an iOS or Android device, see

www.vern ier. com/t il/3630

In order to calibrate a Tris-Compatible Flat pH Sensor or to confirm that a saved
pH calibration is accurate, you should have a supply of pH buffer solutions that
cover the range of the pH values you will be measuring. For more information
about pH buffer solutions, including recipes for preparation, see

www.vern ier. com/t il/3625

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Specifications

Type Double-junction, sealed, gel-filled, polycarbonate body,

Ag/AgCl

Response time 90% of final reading in 1 second in a buffer

Temperature range 5 to 80°C (readings not compensated)

Range pH 0–14

Accuracy ± 0.2 pH units

Isopotential pH pH 7 (point at which temperature has no effect)

Default calibration
values

slope: –7.78

intercept: 16.34

Shaft diameter 12 mm OD

Membrane style Flat glass

Cable 1 meter coaxial cable with BNC connector

Care and Maintenance

Short-term storage (up to 24 hours): Place the electrode in pH 4 or pH 7 buffer
solution. It should never be stored in distilled water.

Long-term storage (more than 24 hours): Store the electrode in a pH 4
buffer/KCl storage solution in the storage bottle. The pH electrode is shipped in
this solution. Vernier sells 500 mL bottles of pH Storage Solution
(order code PH-SS), or you can prepare additional storage solution by adding 10 g
of solid potassium chloride (KCl) to 100 mL of pH 4 buffer solution. Vernier sells
a pH Buffer Capsule kit (PH-BUFCAP) that includes a buffer solution preservative.
Storing the electrode in this solution contributes to electrode longevity and retains
electrode response time when the unit is placed back into service.

If the electrode is inadvertently stored dry for a short period of time, immerse the
tip in the pH 4 buffer/KCl storage solution for a minimum of 8 hours prior to use.
If the readings are still not accurate after calibration or if the response is slow, try
shocking the sensor as described in the Troubleshooting section.

How the Sensor Works

The Tris-Compatible Flat pH Sensor is a sealed, gel-filled, double-junction
pH Electrode attached via BNC to our Electrode Amplifier. The double-junction
pH Electrode prevents silver from the Ag/AgCl gel from coming in contact with
the sample. Tris buffers (tris(hydroxymethyl)aminomethane) and solutions with
proteins and sulfides will react with silver to clog the reference junction,
shortening the life of single-junction electrodes.

The measurement electrode is made of flat glass, making it more durable and easier
to clean than a traditional glass bulb. In addition to liquids, it is ideal for
measuring the pH of semisolids such as many foods and soil slurries. It also allows
for flat surface measurements and the use of smaller sample sizes.

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The Electrode Amplifier that is included with the sensor amplifies the electrode’s
mV reading into the appropriate range for the interface. It also provides the
software with the calibration values that convert the voltage into a pH value.

Troubleshooting

When testing a Tris-Compatible Flat pH Sensor, it is best to measure a buffer
solution because it is easier to determine if the sensor is reading correctly. Do not
test your sensor by measuring distilled water. Distilled water can have a pH
reading in the range of 5.5–7.0, due to varying amounts of dissolved carbon
dioxide. Furthermore, due to a lack of ions, the pH values reported with the sensor
in distilled water will be erratic.

If your Tris-Compatible Flat pH Sensor is reading differently from the pH of a
buffer solution (e.g., reads 6.7 in a buffer 7), you may simply need to calibrate the
sensor. See the Calibration section for more information.

If your readings are off by several pH values, the pH readings do not change when
moved from one buffer solution to a buffer solution of different pH, the sensor was
stored dry for an extended period of time, or the sensor’s response seems slow, the
problem may be more serious. A method called “shocking” can be used to revive
pH electrodes. To shock your pH Sensor, perform the following:

1. Soak the pH Electrode for 4–8 hours in an HCl solution of 0.1 M–0.5 M.

2. Rinse off the electrode and soak the tip in freshly prepared long-term storage
solution (recipe above) for 30–60 minutes.

3. Rinse the electrode and test it with buffer solutions of known pH.

Occasionally, mold will grow in the pH 4 buffer/storage solution. Mold will not
harm the electrode and can easily be removed using a mild detergent solution.
Mold growth in the storage solution can be inhibited by adding a buffer
preservative.

For additional troubleshooting and FAQs, see

www.vern ier. com/t il/1361

Repair Information

If you have followed the troubleshooting steps and are still having trouble with
your Tris-Compatible Flat pH Sensor, contact Vernier Technical Support at
[e-mail] or call 888-837-6437. Support specialists will work with you
to determine if the unit needs to be sent in for repair. At that time, a Return
Merchandise Authorization (RMA) number will be issued and instructions will be
communicated on how to return the unit for repair.

Accessories/Replacements

Item Order Code

pH Storage Solution, 500 mL

PH-SS

pH Buff er Cap sules (3×10) Kit

PH-BUFCA P

Storage Solution Bottles, pkg of 5

BTL

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