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The SmarTesterPC for dissolved oxygen solves many of the problems associated with measuring oxygen in liquids, particularly those that are not flowing or that have suspended solids in them.

 

Why are on-line dissolved oxygen measurements difficult to do well?

Oxygen sensors in liquid can be fouled by suspended solids and are subject to chemicals that cause interferences.

 

Oxygen sensors are temperature dependent. If they are immersed in liquid, the temperature of the sensor reflects the temperature of the liquid, which can be changing, sometimes rapidly.

 

Most dissolved oxygen sensors require liquid flow to prevent a "blanket" of de-oxygenated liquid from introducing false readings. Most dissolved oxygen sensors are calibrated in air (for example in the atmosphere at 20.9% oxygen) and then used to make low level measurements in liquid. This can introduce calibration error.

 

Most dissolved oxygen sensors have to be pulled out of the system for maintenance or replacement causing operational down-time. These sensors must be calibrated manually. Since sensor calibration is sufficiently time-consuming and costly in terms of down-time, it is not performed often enough to provide any assurance that the sensor is calibrated properly. Operators that test for oxygen at various points in their system never know if all their oxygen sensors are calibrated the same way. If there is drift in one or more sensors, the operator isn't aware of it between calibration checks.

 

If these problems with on-line dissolved oxygen measurements concern you, consider how theSmarTester's unique features address these problems.

 

The sensor never touches the liquid so there is no fouling.

Potential interferences in the liquid cannot affect the sensor, including temperature gradients or rapidly changing temperature. (Since the sensor is not in the liquid, it is not affected by liquid temperature.)

 

The sensor can be replaced or pulled for maintenance without affecting on-going operations.

 

One sensor can be used for testing liquids automatically from multiple sources. As a result all testing is done with one sensor and one calibration. The SmarTester can be situated in your laboratory or close to the liquid source.

The sensor can be calibrated in place.

 

Calibration is automatic. You can check the calibration and/or recalibrate as often as you like. Calibration records can be part of your dissolved oxygen measurement records.

The calibration standard -- air from the atmosphere -- is authoritative and repeatable. However, since small injections of air are used to calibrate the sensor, the calibration is more precise. There is never any question as to whether your sensor or system is in calibration.

The SmarTester dissolved oxygen monitoring system meets the exacting requirement for low level oxygen measurements. The system utilizes "Clark" cell polarographic sensor technology plus proprietary electronics and software. Other sensors are available, galvanic and zirconium oxide.

• Sensor accuracy and repeatability: +/- 0.01 mg/ltr.
• System accuracy and repeatability: +/- 0.1 mg/ltr.

The design of the unit represents a sophisticated blend of concept and application. It incorporates:
• Long established testing methodology
• Proven electronic and mechanical technology
• Long-term reliability and ease of on-site maintenance
• Ease of calibration
• RS232 communication capability

The SmarTester is available in a variety of sensor configurations. In addition to oxygen these include pressure, temperature, flow, conductivity, pH, carbon dioxide or any other parameter for which there is an electronic sensor. The unit can be integrated with other instruments through the use of the LS/QA System Controller into one automated testing module.

Oxygen, Dissolved, In-line, Water and Wastewater

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