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Overview
The CS526 probe measures pH using state-of-the-art ISFET technology. There is no glass bulb to break, making the probe safer and more rugged. The probe is easy to clean, and can be stored dry.
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Benefits and Features
- Innovative ISFET pH-sensing element
- Easily cleaned
- More rugged than the traditional glass electrode pH probes
- Each sensor individually tested
- Designed and manufactured under stringent quality control conditions in an ISO 9001 environment
- CE compliant
Please note that this product has a six-month warranty.
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Detailed Description
The CS526 uses SENTRON’s high-tech, ion sensitive field effect transistor (ISFET) semiconductor as its pH-sensitive element, and includes a silver/silver chloride– potassium chloride reference system. The CS526’s design allows it to be suitable for a variety of liquid pH-monitoring applications. The electronics are safely embedded in a durable PEEK body. Elimination of the glass bulb removes the possibility of broken glass, making the CS526 more rugged and safer to use.
Note: Campbell Scientific warranty does not cover a clogged reference diaphragm or improperly cleaned or maintained ISFET chip. (See the Maintenance section in the instruction manual for more information.)
This sensor requires the 5 V output on the data logger to be powered..
Specifications
| pH Range | 2 to 12 |
| Power Requirements | 5 Vdc |
| Current Consumption | 15 mA (maximum) |
| Accuracy | ±0.2 pH (over 10° to 40°C) |
| Operating Temperature Range | 10° to 40°C |
| Output |
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| 24 h Drift | < 0.15 pH (after 15 min. soak in pH 7 at 25°C) |
| Allowed Water Pressure | 0 to 700 kPa (0 to 101.5 psi) |
| Cable Type | Three-twisted pair, 24 AWG cable with Santoprene jacket |
| Sensor Material | Polyetheretherketone (PEEK) |
| Maximum Cable Length | 100 m (328 ft) |
| Diameter | 16 mm (0.63 in.) |
| Length | 102 mm (4 in.) |
| Weight | 318 g (11.2 oz) with 3.05 m (10 ft) cable |
Compatibility
Please note: The following shows notable compatibility information. It is not a comprehensive list of all compatible products.
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Frequently Asked Questions
Number of FAQs related to CS526-L: 14
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The source and the drain are two of the three electrodes contained within the ISFET chip, and they behave in much the same way. The third electrode in the ISFET chip, the gate, has an electrical field that influences the current that flows between the source and the drain. The electrical potential in the ISFET pH sensor is measured between the reference electrode and the source.
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The CS526-L pH sensor uses an ISFET chip instead of pH-sensitive glass, which is used for many other pH sensors. The ISFET chip is a transistor coated with a chemically sensitive material. One of the ISFET chip’s electrodes (the gate) and the reference electrode are submersed in the same sample solution. A circuit path is established between the two electrodes. The difference in electrical potential between the two electrodes is directly proportional to the sample solution’s pH. Thus, by measuring the electrical potential, the pH is measured.
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Silver is the best electrical conductor of all the metals because it has the lowest electrical resistance. The silver wire, coated in silver chloride, is relatively insensitive to changes in temperature.
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In an ISFET chip pH sensor, the chemical coating on the gate electrode can vary depending on the model and manufacturer of the pH sensor. Depending on which chemical coating is used and what elements are present in the sample solution, there may be some ion interference.
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Cleaning and/or calibration may be required when the measurements are scattered, drifting occurs, or there is physical evidence of fouling. Measurements for pH must be monitored regularly to check for scattering. However, just because the results are scattered does not necessarily indicate the need for an adjustment. For example, there may be a change in the water source that causes the scattering. As a sensor ages, however, the scattering of the measured values tends to increase.
To check the performance of a pH sensor, use it to measure a buffer solution in the correct range. If the value returned is within the specified range, the sensor does not need to be calibrated.
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An ISFET chip pH sensor has three main components:
- ISFET chip—The ISFET chip is made of durable plastic and contains three electrodes: the source, the drain, and the gate. The gate is the ISFET chip’s only electrode that comes in contact with the sample solution.
- Reference electrode—Inside the reference electrode’s membrane, there is a silver wire element submersed in an electrolyte solution. The reference electrode, as a whole, is submersed in the sample solution.
- Reference junction—The reference junction is located at the end of the reference electrode by the sample solution. It interacts with both the reference electrode’s electrolyte solution and the sample solution to complete the electrical circuit.
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PolyEtherEtherKetone (PEEK) is a plastic material that has very good thermal stability and chemical resistance properties. This material was chosen for use in the manufacture of the CS526-L because of its natural resistance to organic acids (acetic, carbonic, citric, tartaric, etc.) and its hydrolysis resistance to fresh and saltwater.
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The recommended calibration method listed in a specific pH sensor’s instruction manual should be followed to guarantee the best results. Calibration must be performed correctly to ensure accurate and repeatable measurements. Before performing calibration, the pH sensor should be cleaned.
Calibration is commonly done using a known-value pH solution called a buffer. The buffer solution is formulated to resist pH changes caused by external contaminants. However, the pH of the buffer solution changes as the temperature changes. To compensate for this, manufacturers list the pH of the buffer solution at various temperatures on the buffer solution’s bottle so that the correct value for calibration is selected.
The most common calibration method is a two-point calibration using two buffer solutions. Each buffer solution has known and accurate pH values at different temperatures. The buffers used should be based on the normal measurement range that the pH sensor operates in for the application. One buffer solution should have a 7.0 pH. The second buffer solution should have a pH that is near the expected pH value of the sample solution.
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A reference electrode can become contaminated when poisoning ions such as lead, iron, chrome, cyanide, or sulfide enter the reference electrode and react either with the silver wire or with the electrolyte solution.
The contamination may not become apparent until the silver-chloride coating is completely dissolved and the electrical potential from the reference electrode has changed greatly. If this occurs, the reference electrode must be replaced.
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In the event that both alkaline and acidic sample solutions are measured using a single pH sensor, a multipoint calibration is done using three buffer solutions. As in the two-point calibration, the first buffer solution has a 7.0 pH. The second buffer solution should be near in pH value to either the acidic or alkaline sample solution, and the third buffer solution should be near in pH value to the other.
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