PRINCIPAL OF OPERATION

The QAS-101 Series Single Point Gas Detector is an economical, stand alone gas detection and control unit. The solid state sensor utilizes a sintered tin dioxide element. When the sensor is heated to a high temperature (typically 400 degrees celcius), free electrons flow easily when no oxygen is present. In clean air, oxygen is absorbed onto the element surface providing a restriction to the electron flow and therefore increasing the electrical resistance of the element. As the sensor is exposed to the target gas, the tin dioxide element absorbs molecules of the target gas causing oxidation in the process. This oxidation reduces the resistance of the element in a known and repeatable manner. The controller electronics measures this change in resistance and compares it to two independent setpoints. Field adjustment of the setpoints is done by multi-turn trim potentiometers. When either of the setpoints is exceeded by the measurement signal, the electronics actuates the associated internal DPDT relay.

FEATURES:

• The contacts of this relay may be used to control ventilation fans, audible devices, visual alarms, or other on-off type equipment
• Power requirement is 115 VAC, 50/60 Hz.
• The controller monitors the input signal and indicates a fail condition if the signal drops below a factory preset level.
• LED status indicator lights are visible at the front of the unit for power on, alarm status, and fail condition.
• The controller is supplied with and internal audio indicator for actuation on high alarm or fail condition.
• Internal DIP switch settings provide time delay for actuation of the relays, audible deactivation, and selection of relay to actuate on fail condition.
• The enclosure is rated Nema 1 general purpose for surface mounting.