Zener diodes and intrinsic safety


Thread Starter


Can any one explain to me how zener diodes are used in flame proof environments. They say it is called intrinsic safety. How does the zener diode play a role here? Can you advise any website which gives an overall idea regarding this topic please. with thanks, vedachalam, veda_n@usa,net

kalpak dabir

considering this and some of your previous queries to this web site you could begin with the reference book "Process/Industrial Instruments and Controls Handbook, 5th Edition" edited by McMillan and Considine, which would give an excellent overview and then follow on its biblography for further info.
hello - Use Intrinsically Safe Zener Diode Barriers to control non-voltage producing sensors in hazardous areas. It simply limits the amount of power to the electrical equipment. The power is below the level necessary to ignite the fuel and oxygen. Information should be on our web any month now. The controls can be placed in an area that supports explosion that is Fuel, Oxygen and Ignition. The ZB is placed in a safe area with only signal wires connecting the dry contact switch. (Which is in the hazardous area.) Explosion proof is a device that can control and contain an explosion within its enclosure. ZB itself is not explosion proof so it is mounted in a safe area - but the control leads (low power) can enter the area. The device must be an approved product e.g. Level switch, RTD, TC, pressure and flow switches for example. USA requires FM, UL and Canada CSA. There are many variations of ZB. Simple On/Off, latching, dual channel etc. Thanks Bob Hogg www.almegcontrols.com

Suresh Kumar Devapiriyam

Hi, The zener diode is connected in reverse bias to the field side terminals and the zener diode does not conduct till the breakdown voltage. Hence the output potential goes to the field instrument located in the hazardous area as long as the voltage is with in the allowable limit. When the voltage level increases, the zener diode conducts and prevents the voltage from reaching the filed instrument, thus preventing any sparking in the filed which could cause an explosion. Zener barriers also have current limiting resistors, fuses, etc. You can visit MTL's web site http://www.mtl-inst.com/ for further details. D.Suresh Kumar Senior Principal Engineer BB-IDEA Limited Chennai - 600 034 India mailto :[email protected] web :http://www.idealtd.com/