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Application
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Your choices are...
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4-20 mA 2-wire Transmitters
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4-20 mA 2-wire Transmitters may also be referred to as analog inputs. Transmitters convert a physical signal to a 4-20 mA electrical signal for transmission. The 80/20 Rule is actually five rules that govern the construction of intrinsically safe analog inputs circuits and the selection of barriers.
- Most analog input circuits are protected by grounded intrinsically safe barriers because of lower costs.
- The conversion resistor is commonly 250 ohms and installed on the negative return.
- Analog input circuits are normally powered by 24 VDC.
- One signal-and-return intrinsically safe barrier will solve most transmitter applications.
- Most hazardous locations are classified as Groups C-G.
Transmitters and current sources are not classified as simple devices. Therefore, Intrinsic Safety Certification is required.
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I/P Converters or Displays
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These are sometimes called analog outputs and can include: 4-20 mA I/P converters, displays, and positioners. I/P Converters are not classified as simple devices. Therefore, Intrinsic Safety (IS) certification is required.
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Switches
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Switches, or digital inputs, include: contacts, mechanical, reed, limit, and float switches. All digital inputs can be made safe with an isolated intrinsically safe relay, commonly referred to as a switch amplifier. The barriers used for digital inputs are the same as used in analog inputs and digital outputs. Mechanical switches do not require Intrinsic Safety (IS) certification.
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Solenoids / Audible Alarms
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Sometimes referred to as digital outputs. Solenoids contain large inductive components. In order to use them in intrinsically safe loops, protective components have to be built into the solenoid itself. Therefore, Intrinsic Safety certification is required. Audible alarms are used in hazardous areas to signal an event has occurred. Typically the choice of which barrier would be the same as it is for solenoids.
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Flow Meters
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Magnetic pickup flow meters are not classified as simple devices. Therefore, Intrinsic Safety (IS) certification is required.
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Infrared Temperature Sensors
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Infrared temperature sensors are not classified as simple devices. Therefore, Intrinsic Safety (IS) certification is required.
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LED Indicating Lights
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LEDs are simple devices and do not require Intrinsic Safety Certification.
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Load Cells
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Load cells are simple devices and do not need Intrinsic Safety (IS) certification. However some manufacturers submit their products for IS certification in order to evaluate heating behavior. In this case, the certification body returns a set of parameters to be applied.
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Potentiometers
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Potentiometers are simple devices and do not require Intrinsic Safety (IS) certification.
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Proximity Switches
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NAMUR (DIN 19324 Standard EEX ia IIc T4) proximity switches are commonly used where areas are required by code to be intrinsically safe.
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RTDs
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RTDs are temperature sensing devices that are classified as simple devices and do not need to be approved as intrinsically safe. One intrinsically safe barrier can be used to protect all 2-, 3-, or 4-wire RTDs. Isolated temperature converters accept signals from temperature sensors and convert them to a mA signal, which is intrinsically safe.
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Strain Gages
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Strain gages are simple devices and do not need Intrinsic Safety (IS) certification. However some manufacturers submit their products for IS certification in order to evaluate heating behavior. In this case, the certification body returns a set of parameters to be applied.
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Thermocouples
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Thermocouples are temperature sensing devices that are classified as simple devices and do not need to be approved as intrinsically safe. One intrinsically safe barrier can be used to protect all thermocouples. Isolated temperature converters accept signals from temperature sensors and convert them to a mA signal, which is intrinsically safe. Consistent wiring is important to provide more accurate signals.
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Other
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Other unlisted, specialized, or proprietary application.
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Search Logic:
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All products with ANY of the selected attributes will be returned as matches. Leaving all boxes unchecked will not limit the search criteria for this question; products with all attribute options will be returned as matches.
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Barrier Type
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Your choices are...
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Galvanic Isolator
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Galvanic isolators provide intrinsically safe connections. In addition, they are used to isolate hazardous and nonhazardous area circuits, either optically or by transformer. Some galvanic isolators may be used as signal conditioners, although most styles are designed application specific. The majority of these isolators require an external power source.
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Zener Barrier (Grounded)
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Zener barriers are passive devices that contain Zener diodes, resistors, and fuses to limit excess voltage and current. These are the basic building blocks which are contained in all other intrinsically safe barriers There is always a voltage drop across Zener barriers because of resistance. Proper selection of the Zener barriers is required as well as a ground connection. The Zener diode barrier works by diverting potentially dangerous energy to ground before it can reach the hazardous area. They limit the fault voltage to the hazardous area. The barrier must protect against dangerous energy and allow the loop to function normally.
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Intrinsically Safe Remote I/O
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Distributed I / O developed specifically for use in hazardous areas.
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Other
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Other unlisted, specialized, or proprietary barrier type.
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Search Logic:
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All products with ANY of the selected attributes will be returned as matches. Leaving all boxes unchecked will not limit the search criteria for this question; products with all attribute options will be returned as matches.
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Electrical Specifications
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Your choices are...
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AC
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Alternating current (AC).
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DC
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Direct current (DC).
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Search Logic:
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All products with ANY of the selected attributes will be returned as matches. Leaving all boxes unchecked will not limit the search criteria for this question; products with all attribute options will be returned as matches.
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Number of Channels
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The maximum number of channels (I/O) supported by the barrier.
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Search Logic:
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User may specify either, both, or neither of the "At Least" and "No More Than" values. Products returned as matches will meet all specified criteria.
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Maximum Open Circuit Voltage (VOC)
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The maximum open circuit voltage (VOC) is the maximum voltage a barrier can deliver to the hazardous area in the case of a fault.
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Search Logic:
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All matching products will have a value less than or equal to the specified value.
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Maximum Short Circuit Current (ISC)
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The maximum short circuit current (ISC) is the maximum current a barrier can deliver to the hazardous area in a fault situation.
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Search Logic:
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All matching products will have a value less than or equal to the specified value.
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Operating Temperature
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This is the full-required range of ambient operating temperature.
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Search Logic:
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User may specify either, both, or neither of the limits in a "From - To" range; when both are specified, matching products will cover entire range. Products returned as matches will meet all specified criteria.
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