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Residual-current device

21/06/2017 Comments off
From Wikipedia, the free encyclopedia
 

An RCD does not provide protection against unexpected or dangerously high current (called spikes or surges) when current is flowing in the usual wires in the circuit, therefore it cannot replace a fuse or protect against overheating or fire risk due to overcurrent (overload) or short circuits if the fault does not lead to current leakage. Therefore, RCDs are often used or integrated as a single product along with some kind of circuit breaker, such as a fuse or miniature circuit breaker (MCB), which adds protection in the event of excessive current in the circuit (the resulting RCD with overcurrent protection called an RCBO). RCDs also cannot detect the situation where a human accidentally touches both conductors at the same time, since the flow of current through an expected device, an unexpected route, or a human, are indistinguishable if the current returns through the expected conductor.

RCDs are usually testable and resettable devices. Commonly they include a button that when pressed, safely creates a small leakage condition, and a switch that reconnects the conductors when a fault condition has been cleared. Depending upon their design, some RCDs disconnect both the energized and return conductors upon a fault, while others only disconnect the energized conductor and rely upon the return conductor being at ground (earth) potential. The former are commonly known as « double-pole » designs; the latter as « single-pole » designs. If the fault has left the return wire « floating » or not at its expected ground potential for any reason, then a single-pole RCD will leave this conductor still connected to the circuit when it detects the fault.

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Ubuntu Check RAM Memory Chip Speed and Specification From Within a Linux System

22/06/2016 Comments off

I want to add more RAM to my server running Ubuntu Linux. How do I find out my current RAM chip information such as its speed, type and manufacturer name within a Linux system without opening the case?

You need to use the dmidecode command which is a tool for dumping a computer’s DMI (some say SMBIOS) table contents in a human-readable format. This table contains a description of the system’s hardware components (such as RAM), as well as other useful pieces of information such as serial numbers and BIOS revision. Thanks to this table, you can retrieve hardware information without having to probe for the actual hardware. Open a command-line terminal (select Applications > Accessories > Terminal), and then type:

$ sudo dmidecode --type memory

OR

# dmidecode --type memory | less

OR

$ sudo dmidecode --type 17

Sample outputs:

# dmidecode 2.10
SMBIOS version fixup (2.51 -> 2.6).
SMBIOS 2.6 present.
Handle 0x0011, DMI type 16, 15 bytes
Physical Memory Array
	Location: System Board Or Motherboard
	Use: System Memory
	Error Correction Type: None
	Maximum Capacity: 4 GB
	Error Information Handle: Not Provided
	Number Of Devices: 4
Handle 0x0012, DMI type 17, 27 bytes
Memory Device
	Array Handle: 0x0011
	Error Information Handle: No Error
	Total Width: 72 bits
	Data Width: 64 bits
	Size: 2048 MB
	Form Factor: DIMM
	Set: 1
	Locator: DIMM#1A
	Bank Locator: Bank 1
	Type: DDR2
	Type Detail: Synchronous
	Speed: 667 MHz
	Manufacturer: Not Specified
	Serial Number: Not Specified
	Asset Tag: Not Specified
	Part Number: Not Specified
Handle 0x0013, DMI type 17, 27 bytes
Memory Device
	Array Handle: 0x0011
	Error Information Handle: No Error
	Total Width: 72 bits
	Data Width: 64 bits
	Size: 2048 MB
	Form Factor: DIMM
	Set: 1
	Locator: DIMM#2A
	Bank Locator: Bank 2
	Type: DDR2
	Type Detail: Synchronous
	Speed: 667 MHz
	Manufacturer: Not Specified
	Serial Number: Not Specified
	Asset Tag: Not Specified
	Part Number: Not Specified
Handle 0x0014, DMI type 17, 27 bytes
Memory Device
	Array Handle: 0x0011
	Error Information Handle: No Error
	Total Width: 72 bits
	Data Width: 64 bits
	Size: 2048 MB
	Form Factor: DIMM
	Set: 1
	Locator: DIMM#1B
	Bank Locator: Bank 1
	Type: DDR2
	Type Detail: Synchronous
	Speed: 667 MHz
	Manufacturer: Not Specified
	Serial Number: Not Specified
	Asset Tag: Not Specified
	Part Number: Not Specified
Handle 0x0015, DMI type 17, 27 bytes
Memory Device
	Array Handle: 0x0011
	Error Information Handle: No Error
	Total Width: 72 bits
	Data Width: 64 bits
	Size: 2048 MB
	Form Factor: DIMM
	Set: 1
	Locator: DIMM#2B
	Bank Locator: Bank 2
	Type: DDR2
	Type Detail: Synchronous
	Speed: 667 MHz
	Manufacturer: Not Specified
	Serial Number: Not Specified
	Asset Tag: Not Specified
	Part Number: Not Specified