Model 1-C DewTrace®
Trace Moisture Analyzer: The DewTrace™ Electrolytic Hygrometer
- Semiconductor industry for monitoring common process gases
- Gas supplier Industry as a quality control instrument
- Electric power industry for checking moisture levels in transformer gases
Benefits:
• Monitors PPMv moisture levels in relatively clean, dry, inert gases
• Electrochemical sensor with proprietary diffusion membrane
• 0.1 to 500 PPMv measurement; sensitivity below 1 PPMv
• Fast response; flow insensitive
The DewTrace Moisture Analyzer utilizes an electrochemical (phosphorus pentoxide-P2O5 coated) sensor in combination with a proprietary semipermeable diffusion membrane. This membrane freely passes water vapor molecules while protecting the sensor from larger molecules which might adversely affect performance. The sensing element itself is an interdigitated wafer electrode and is manufactured using a unique procedure. It doesn't utilize a wire wound component.
The interconnecting cable length between the sensor housing and electronics is of minor importance since the sensor outputs a DC current. A six-foot length is provided. The electronics unit supplies power for the sensor and converts the received analog signal into a moisture value in PPMv which is then digitally displayed on the front panel. The electronics is equipped with a stand-by position on the function switch which allows the cell to remain dry when not sampling, and which also gives indication of proper functioning of the cell. This feature significantly reduces or eliminates the amount of drying time prior to startup. The electronics is also equipped with a Cell Life Indicator which displays the useful life of the sensing element. If the sensing element is replaced, a Calibration Digital Switch, located on the rear panel, matches the new element to the electronics.
Principle of Operation:
The electrochemical cell consists of a hygroscopic material, phosphorus pentoxide (P2O5), coated on a semiconductor electrode element. Voltages are applied to the electrodes such that adequate field strength is obtained to dissociate absorbed water into hydrogen and oxygen, The current flowing is proportional to the quantity of water dissociated (Faraday's Law of Electrolysis). Thus, this instrument, which measures the dissociation current, makes a fundamental measurement of the moisture present.
Features:
This sensor design is easy to install, use, and maintain. The sensing element and membrane are mounted in a rugged 316SS stainless steel housing. The sensor assembly can be used in-situ with its own mounting flange, or it can be used in a flow stream with the optional 316 Stainless Steel Sample Chamber. It is less subject to contamination than other sensors because of the membrane. Also, when other oxide sensors fail, the whole sensor often needs to be replaced-a very costly procedure. In this sensor, only the membrane and/or wafer electrode would require replacement-an easy,inexpensive task. Measurements are very repeatable. Since measurements are independent of the mass of gas, the inaccuracies and calibration problems associated with most other electrochemical sensors are eliminated.
Note:
The instrument should not be used with gases which are corrosive, or which readily combine with phosphorus pentoxide to form water. Gases and materials that should be avoided include certain acids, alcohol, chlorine, fluorine, hydrogen chloride, hydrogen fluoride, amines, ammonia, alkynes, alkadienes, and alkenes.
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