Relative Humidity System

The Sartrex Relative Humidity System is designed to measure the moisture content in the gases from eight different process lines in the range of -40C to +10C. The direct measurement of water vapor pressure in each process line is accomplished by using the Panametrics M series aluminum oxide moisture sensor and Panametrics Moisture Target Series 5 hygrometer (Transmitter / Signal conditioner).

The sensor (M series) consists of an aluminum strip which is anodized by a special process to provide a porous oxide layer over which a very thin coating of gold is evaporated. The aluminum base and the gold layer form the two electrodes of what is essentially an aluminum oxide capacitor.

Water vapor is rapidly transported through the gold layer and equilibrated on the pore walls of the oxide layer. The number of water molecules absorbed on the oxide structure determines the conductivity of the pore walls. Each value of pore wall resistance provides a distinct value of electrical impedance which in turn is functionally related to the water vapor pressure.

The M Series moisture probe is coupled to a Panametrics hygrometer (Moisture Target Series 5) by an interconnecting cable. The Moisture Target Series 5 is a microprocessor-based hygrometer that measures moisture content in gases. The Series 5 displays measurement data on a one-line, 6-digit liquid crystal display and also provides a single analog output (4-20mA loop).

Each Moisture Target Series 5 (Transmitter/Signal Conditioner) accepts 24V DC from the Power Supply. The Power/Signal cables (24.4 meter length) which are provided with this system can be used to power up the Series 5 hygrometers and at the same time transfer the signals (4-20mA) to the Signal Termination terminal blocks of the Power Supply.

The system is powered up by a 19″ rack mount Power Supply which accepts line voltage of 120V AC. This Power Supply provides eight channels and each channel consists of 24V DC and Signal termination terminal blocks.