pH Sensor (Order Code PH-BTA) Our pH Sensor can be used for any lab or demonstration that can be done with a traditional pH meter. This sensor offers the additional advantages of automated data collection, graphing, and data analysis. Typical activities using our pH sensor include studies of household acids and bases, acid-base titrations, monitoring pH change during chemical reactions or in an aquarium as a result of photosynthesis, investigations of acid rain and buffering, and investigations of water quality in streams and lakes. Collecting Data with the pH Sensor This sensor can be used with the following interfaces to collect data: • Vernier LabQuest® as a standalone device or with a computer • Vernier LabQuest® Mini with a computer • Vernier LabPro® with a computer, TI graphing calculator, or Palm® handheld • Vernier Go!®Link • Vernier EasyLink® • Vernier SensorDAQ® • CBL 2™ Here is the general procedure to follow when using the pH Sensor: 1. Connect the pH Sensor to the interface. 2. Start the data-collection software1. 3. The software will identify the pH Sensor and load a default data-collection setup. You are now ready to collect data. Important: Do not fully submerge the sensor. The handle is not waterproof. Data-Collection Software This sensor can be used with an interface and the following data-collection software. • Logger Pro 3 This computer program is used with LabQuest, LabQuest Mini, LabPro, or Go!Link. • Logger Pro 2 This computer program is used with ULI or Serial Box Interface. • Logger Lite This computer program is used with LabQuest, LabQuest Mini, LabPro, or Go!Link. • LabQuest App This program is used when LabQuest is used as a standalone device. • EasyData App This calculator application for the TI-83 Plus and TI-84 Plus can be used with CBL 2, LabPro, and Vernier EasyLink. We recommend version 2.0 or newer, which can be downloaded from the Vernier web site, www.vernier.com/easy/easydata.html, and then transferred to the calculator. 1 If you are using Logger Pro 2 with either a ULI or SBI, the sensor will not auto-ID. Open an experiment file for the pH Sensor in the Probes & Sensors folder. 2See the Vernier web site, www.vernier.com/calc/software/index.html for more information on the App and Program Transfer Guidebook. • DataMate program Use DataMate with LabPro or CBL 2 and TI-73, TI-83, TI-84, TI-86, TI-89, and Voyage 200 calculators. See the LabPro and CBL 2 Guidebooks for instructions on transferring DataMate to the calculator. • Data Pro This program is used with LabPro and a Palm handheld. • LabVIEW National Instruments LabVIEW™ software is a graphical programming language sold by National Instruments. It is used with SensorDAQ and can be used with a number of other Vernier interfaces. See www.vernier.com/labview for more information. pH Electrode Specifications Type: Sealed, gel-filled, epoxy body, Ag/AgCl Response time: 90% of final reading in 1 second Temperature range: 5 to 80°C 12 mm OD Range: pH 0–14 13-bit Resolution (SensorDAQ): 0.0025 pH units 12-bit Resolution (LabQuest, LabQuest Mini, Go!Link, LabPro, ULI, SBI): 0.005 pH units 10-bit Resolution (CBL 2): 0.02 pH units Isopotential pH: pH 7 (point at which temperature has no effect ) Output: 59.2 mV/pH at 25°C Stored Calibration Values2: Intercept (k0): 13.720 Slope (k1): –3.838 NOTE: This product is to be used for educational purposes only. It is not appropriate for industrial, medical, research, or commercial applications. How the pH Sensor Works The pH Amplifier inside the handle is a circuit which allows a standard combination pH electrode (such as the Vernier 7120B) to be monitored by a lab interface. The cable from the pH Amplifier ends in a BTA plug. The pH Sensor will produce a voltage of 1.75 volts in a pH 7 buffer. The voltage will increase by about 0.25 volts for every pH number decrease. The voltage will decrease by about 0.25 volts/pH number as the pH increases. The Vernier gel-filled pH Sensor is designed to make measurements in the pH range of 0 to 14. A polycarbonate body that extends below the glass sensing bulb of the 2 These are average calibration values. Actual values may vary because sensors are individually calibrated by Vernier before shipping.3electrode makes this probe ideal for the demands of a middle school, high school, or university level science class or for making measurements in the environment. The gel-filled reference half cell is sealed—it never needs to be refilled. This sensor is equipped with circuitry that supports auto-ID. When used with LabQuest, LabQuest Mini, LabPro, Go! Link, SensorDAQ, EasyLink, or CBL 2, the data-collection software identifies the sensor and uses pre-defined parameters to configure an experiment appropriate to the recognized sensor. Preparing for Use To prepare the electrode to make pH measurements, follow this procedure: • Remove the storage bottle from the electrode by first unscrewing the lid, then removing the bottle and lid. Thoroughly rinse the lower section of the probe, especially the region of the bulb, using distilled or deionized water. • When the probe is not being stored in the storage bottle, it can be stored for short periods of time (up to 24 hours) in pH-4 or pH-7 buffer solution. It should never be stored in distilled water. • Connect the pH Sensor to your lab interface, load or perform a calibration (as described in the next section), and you are ready to make pH measurements. Note: Do not completely submerge the sensor. The handle is not waterproof. When you are finished making measurements, rinse the tip of the electrode with distilled water. Slide the cap onto the electrode body, then screw the cap onto the storage bottle. Note: When the level of storage solution left in the bottle gets low, you can replenish it with small amounts of tap water the first few times you use the probe (but not indefinitely!). A better solution is to prepare a quantity of pH-4 buffer/KCl storage solution (see the section on Maintenance and Storage) and use it to replace lost solution. Do I Need to Calibrate the pH Sensor? We feel that you should not have to perform a new calibration when using the pH Sensor for most experiments in the classroom. We have set the sensor to match our stored calibration before shipping it. You can simply use the appropriate calibration file that is stored in your