Vernier O2-BTA Users guide

O2Gas Sensor

(Order Code O2-BTA)

The O2Gas Sensor can be used to monitor gaseous oxygen
levels in a variety of biology and chemistry experiments.
The sensor is intended for measuring gaseous, not aqueous,
O2concentrations.

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

l O

Gas Sensor

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l 250 mL gas sampling bottle (Nalgene

Compatible Software and Interfaces

See www.vernier.com/manuals/o2-bta for a list of interfaces and software compatible
with the O2Gas Sensor.

Getting Started

1. Connect the sensor to the interface (LabQuest Mini, LabQuest 3, etc.).

2. Start the appropriate data-collection software (Graphical Analysis, LabQuest
App, Logger Pro) 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 collect data.

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.vernier.com/start/o2-bta

Using the Product

Connect the sensor following the steps in the Getting Started section of this user
manual. Note: For best results, keep the sensor upright as much as possible during
use. Reading may drift if used in a horizontal position.

Videos

View videos related to this product at www.vernier.com/o2-bta

®

bottle with lid)

1. Connect the sensor to your device following the instructions in the Getting
Started section.

2. Open the Calibration menu and choose Calibrate Now.

3. Hold the sensor upright. Using a pointed object, such as a straightened paper
clip, push and hold the zero button. The button is located on the side of the
sensor next to CAL. The voltage should be less than 0.4 V when the button is
depressed.

4. Enter a value of 0% for this reading. Select Keep.

5. Release the zero button.

6. Take a second reading. Keep the sensor upright and expose it to open air. The
voltage should be 1.8 V or greater. If less than 1.8 V, see the Care and
Maintenance section of this user manual.

7. Enter a value of 20.9% oxygen or a corrected value from the table in the Effect
of Humidity section of this user manual. Select Keep.

8. Once finished, the sensor should now read 20.9% (or the value entered from
the table).

9. Save the calibration to the sensor following the steps for the software you are
using. For detailed instructions on calibration see the related links below.

l For instructions on calibration using Logger Pro computer software, see

www.vernier.com/til/2341

l For instructions on calibration using LabQuest App, see

www.vernier.com/til/3394

l For instructions on calibration using Graphical Analysis, see

www.vernier.com/til/3631

l For instructions on calibration using Graphical Analysis with an iOS or

Android device, see www.vernier.com/til/3630

Effect of Humidity

Because the oxygen concentration varies with the amount of water vapor in the
atmosphere, you may want to adjust your atmospheric oxygen calibration value to
improve accuracy when using the O2Gas Sensor. The accepted value of 20.9% for
atmospheric oxygen levels is calculated in dry air (0% humidity). If you know the
relative humidity of the location at which you are calibrating, you can substitute
one of the values below in place of 20.9%.

Relative humidity 0% 25% 50% 75% 100%

Oxygen in % by volume 20.9 20.7 20.5 20.3 20.1

Calibration

For many measurements, it will not be necessary to calibrate the O2Gas Sensor.
The sensor is shipped with a stored calibration. However, this calibration will drift
over time, so periodic calibration is recommended.

A two-point calibration can be done following the procedure below.

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Specifications

Range 0–27% (0–270 ppt)

Accuracy ± 1% volume O2(at 760 mmHg)

Resolution 0.01%

Warm up time < 5 seconds

Response time 90% of final reading in ~12 seconds

How the Sensor Works

The Vernier O2Gas Sensor measures the oxygen concentration in the range of 0 to
27% using an electrochemical cell. The cell contains a lead anode and a gold
cathode immersed in an electrolyte. Oxygen molecules entering the cell are
electrochemically reduced at the gold cathode. This electrochemical reaction
generates a current that is proportional to the oxygen concentration between the
electrodes. The sensor output is a conditioned voltage proportional to the reaction
current.

Output signal range 0.3 to 5 VDC; 2.7 to 3.8 VDC @ 21%

O

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Output impedance 1 KΩ

Input voltage 5 VDC +/–0.25 VDC

Gas sampling mode Diffusion

Normal operating temperature range 20 to 30°C

Storage temperature range –20 to +60°C

Pressure range 0.5 to 1.5 atm

Pressure effect Directly proportional

V

= V

out

(standard) × (P/1013)

out

Default calibration values l slope: 6.6524 %/V

l intercept: –2.05%

Dimensions Sensor tube: 45 mm length, 28 mm OD

Total length: 135 mm

Care and Maintenance

Important: The O2Gas Sensor must be stored upright when not in use. This is
necessary to maintain the sensor. Failure to store upright will shorten the life of
the sensor.

As your O2Gas Sensor ages, the readings will decrease. This is normal, as the
chemicals in the electrochemical cell are depleted. It does not mean the sensor is
no longer functional; rather, it simply requires that you perform a calibration and
store it as described previously. Once the readings in air are below 12% prior to
calibration, or 1.8 volts during calibration, the sensor should be replaced. You may
choose to have your sensor refurbished and a new element installed, or you may
purchase a new sensor.

For tips on how to extend the life of the O2Gas Sensor, see

www.vernier.com/til/2588

Troubleshooting

l Even though the sensor responds rather quickly to changes in

O2concentration, the gas has to diffuse into the electrochemical cell located at
the top of the sensor shaft before any changes in concentration can be detected.
Because the diffusion of a gas is a slow process, there can be some delay in
readings.

l To collect data in a controlled environment, we recommend that you use the

250 mL Nalgene collection bottle that is included with your sensor. Place the
tip of the sensor into the opening of the bottle and push the sensor into the
bottle. When the sensor will go no further, you have a seal. Very important:
Do not place the sensor into any liquid. The sensor is intended only for
measuring gaseous, not aqueous, O2concentration.

l To collect data in a controlled environment and also use our CO

Gas Sensor,

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we recommend purchasing either the BioChamber 250 (250 mL capacity) or
the BioChamber 2000 (2 L capacity). The BioChambers have two openings
with grommets so that you can insert both the CO2Gas Sensor and the O2Gas
Sensor to take measurements of the atmosphere inside the BioChamber
simultaneously.

Repair Information

If you have watched the related product video(s), followed the troubleshooting
steps, and are still having trouble with your O2Gas 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.

For information on common repairs for the O2Gas Sensor, see

www.vernier.com/til/1605

Accessories/Replacements

Item Order Code

BioChamber 250

BioChamber 2000

250 mL Nalgene Bottle w/Lid

BC-250
BC-2000
CO2-BTL

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