Hygrometer

A Combustible gas detector, a hygrometer or a trace oxygen analyzer can be added to generator as option. One, two or all of these instruments can be connected to generator. They each transmit a 4-20 mA signal and are wired directly to the PLC.

The combustible gas detector uses catalytic bead sensor to monitor the presence of hydrogen in te room. The sensor uses two alumina beads surrounded by platinum wire and heated to a high operating temperature. One beads is catalyzed to promote reaction with the combustible gas. The other bead does not react with combustibles and serves as a reference.


The two beads are placed in seperate legs of a wheastone bridge circuit and are exposed to same condition. The electrical resistance of the catalyzed bead increase as the bead heats up in the presence of a combustible gas. The output of the wheatstone bridge changes to signal the combustible concentration. The sensor output is 4-20 mA corresponding to 0 to 100% of the lower explosion limit (LEL) of hydrogen in air.

Hygrometer
Moisture in hydrogen product from generator is monitored with an in-line hygrometer. The hygrometer uses an aluminum oxide moisture sensor. Water molecules which are absorbed on the oxide structure of the sensor effect thr electrical capacitance of the material.

The amount of water is a function of the vapor pressure of the gas being sampled which corresponds to an electrical impedance measure by the sensor.
The sensor output is 4-20mA corresponding tp -90 to 10 degree celcius dew point.

Trace Oxygen Analyzer
An oxygen analyzer is used to monitor trace amounts of oxygen in a sample of the hydrogen before going to storage.

The analyzer uses an electrolytic fuel cell which produce an electric output proportional to the amount of oxygen being consumed. The instrument can be selected to operate within two different scale ranges. The ranges are 0-25% and 0-10ppm. The instrument output is 4-20mA corresponding to the full range of the selected scale.