Barrel Heaters - Hasmak.com.tr

W A T L O WReference DataPower ControllersFour Basic TypesContinued2. Mercury Displacement Relay(MDR)In-boundElectrodePlungerField CoilLiquidMercuryOut-boundElectrodeWatlow No Longer ManufacturesMercury Displacement Relays(MDRs)Because MDRs contain mercury, theyshould not be placed in normal wastestreams (trash barrel). Mercury islisted as a hazardous material andtherefore all MDRs are required bylaw to be recycled and or disposed ofproperly. To promote the responsiblehandling of mercury Watlow hasprovided the following link to anapproved recycling facility:http://www.watlow.<strong>com</strong>/products/controllers/co_mdr.cfm3. Solid State Relays Solid state switching devices have Because solid state relays can operateno moving parts and consequently,at much faster cycle times thanno mechanical failures. Solid state electromechanical relays, they shouldAC Outputswitches are resistant to shock and be employed where extremely tightvibration. The absence of moving process control is required.parts also makes them noise-free Disadvantages of solid state relays(they produce no audible sound). include the inability to provide a positivecircuit break, the initial cost andThe most important factor affectingservice life is its ambient operating their failure mode when misapplied ortemperature. Solid state devices are subjected to overrated conditions.very durable, if they are operated The failure modes include burnout ofwithin tolerable ambient temperatures.Failure to dissipate the heat out; reduction in switching capabilitiesthe switch if the system heater shortsgenerated by any solid state <strong>com</strong>ponentwill quickly destroy it. Location susceptibility to failure caused by lineas the ambient temperatures rise; andand heatsinking must be adequate. transients and inductive loads.Watlow solid state relays accept a These failure modes can be eliminatedto a great degree by proper fusingtime proportioned or on-off signalfrom a controller.of switches for overload conditions,Watlow’s solid state relays change increasing the heat sinking (the overallDC Inputsize) for high ambients, and filter-state near zero volts, which is burstfiring. They are also optically isolated, ing for the transients and inductivewhich means the output circuitry is loads. Each of these will increaseenergized by infrared light striking a the cost of the solid state relay.photosensitive device. This minimizeselectrically generated noise, plusoutput to input electrical isolation.Resources and InformationReference DataTeflon ® is a registered trademark of E.I. du Pontde Nemours & Company.405