Gas Tank Lid Monitoring Sensor REED RELAYS REED SENSORS REED SWITCHES Introduction In and around the gas tank and its filling lid is consider a highly explosive area. Anything that can possible cause a spark could potentially ignite the fuel. Use of an electromechanical sensor to detect if the lid and fuel cap are in place could potential cause a spark across the sensor contacts. Detecting if the lid and gas cap are in place designers have turned to the Reed Sensor which uses hermetically sealed reed switches, and are further packaged in a tough plastic encapsulation. Figure 1. MK14 Sensor physical layout Features • The reed switch used in the Reed Sensor is hermetically sealed and is therefore not sensitive and therefore any sparks across the contacted are hermetically sealed from the environment • EX approved and intrinsically safe available • The hermetically sealed reed switch is ideally suited for switching low signal level voltages and currents which do not draw an arc Figure 2. Gas tank lid with magnet is closed activating reed switch contacts to remain closed. • Magnet and Reed Sensor are isolated and have no physical contact by typically having the magnet mounted to the lid and the Reed Sensor mounted on the gas cap • The magnet is not affected by its environment • Millions of reliable operations • Cylindrical hole and screw fastening mounting • Contacts dynamically tested • Large sensing distances possible Applications • Ideal for sensing gas lid closure and gas cap in place. • Ideal for applications sensing closure of an assortment of different lids and/or caps Figure 3. When gas tank lid is opened the magnet moves away from the reed swtich sensor causing the contacts to open which activated an alarm. Reed Sensors are Ideal for Sensing Gas Lid and Gas Cap are in Place The immediate area in and around the gas cap can be defined as having a potential explosive atmosphere. Any potential arc or spark could ignite the gasoline. Gas lids and gas caps can easily be forgotten to have closed either by the vehicle operator or by a service attendant. Furthermore, with gasoline prices continuing to rise, gasoline theft directly from the tank is on the rise. MEDER electronic Application MEDER electronic AG | Germany | tel.: +49(0)7731/8399-0 | Email: [email protected] MEDER electronic Inc. | USA | tel.: +1 508.295.0771 | Email: [email protected] Page 1 of 2 www.meder.com Gas Tank Lid Monitoring Sensor REED RELAYS REED SENSORS REED SWITCHES Specifications Operate specs Min Max Units Must close distance 5 25 mm Must open distance 5 25 mm Hysteresis Load Characteristics Switching voltage Switching current Carry current Contact rating Static Contact resistance Dynamic contact resistance Breakdown voltage voltage Operate time Release time Operate Temp Storage Temp Typical 50% Min Max Units 200 0.5 1.5 10 150 200 320 0.5 0.1 -20 85 -20 85 V Amps Amps Watts mΩ mΩ V msec msec °C °C To solve the above three problems, designer are now going to Reed Sensors. The sensor indeed serves three purposes: 1 It eliminates the potential of an arc or spark across its contacts making it to the outside world by using hermetically sealed reed switches. In this case, any arc or spark occurring across the contacts is enclosed in the hermetically sealed atmosphere of the reed switch, eliminating itself as a potential ignition device. 2. Generally, a magnet is mounted on the gas lid and the reed sensor is mounted on the gas cap. If both are not in place a signal is sent to the on-board computer locking the ignition system not allowing the vehicle to be turned on. 3. If the car is in the locked position and an attempt is made to remove the gas lid, this also triggers the onboard computer, which sounds an alarm. MEDER’s line of EX approved intrinsically reed sensors are ideal for this application. Electromechanical switches are not hermetically sealed and therefore any arc or spark generated across its contacts could represent a potential ignition point. MEDER’s reed sensors are available in several packages with various connector or lead options allowing the users to meet exact design details. Because of the multitude of design requirements, MEDER has the capability of developing specialized packaging for both the reed sensor and the magnet to meet the user’s specific needs. Consider some of the below option standard options as well. Cylindrical Panel Mount Series Series MK03 MK03 Dimensions mm Dia 5.25 L 25.5 Illustration inches 0.207 1.004 MK14 MK14 Dia L 4 25.5 0.157 1.004 MK18 MK18 Dia L 5 17 0.197 0.669 MK20/1 MK20/1 Dia L 2.72 10 0.107 0.394 Rectangular Screw Flange Mount Series Series MK04 MK05 MK05 Dimensions mm W 13.9 H 5.9 L 23.0 W 19.6 H 6.1 L 23.2 Illustration inches 0.547 0.232 0.906 0.772 0.240 0.913 W 14.9 0.587 H 6.9 0.272 L 32.0 1.260 **Consult the factory for more options not listed above. ** MK12 MK12 MEDER electronic Application MEDER electronic AG | Germany | tel.: +49(0)7731/8399-0 | Email: [email protected] MEDER electronic Inc. | USA | tel.: +1 508.295.0771 | Email: [email protected] Page 2 of 2 www.meder.com