The DC Power Supply is a rather fundamental electronic device, however there are hundreds of DC Power Supply products on the market from dozen of manufacturers. Narrowing down the best product for your application and budget can be a daunting task. This article addresses DC Power Supply differentiators, functions and the applications they are best suited for. The article’s focus is DC Power Supplies used by engineers, manufacturers, quality professionals and electronic hobbyists for the purposes of R&D, manufacturing and testing.
Power Supplies can range in price from $50 to $20,000 and the cost is often directly proportional to the amount of power the device outputs. The primary function of a power supply is to regulate output voltage and current. It takes an input power and regulates the output power as to enforce a constant voltage and current. In the case of DC Power Supplies, the input power is converted from alternating current (AC) to direct current (DC). There are two basic types of regulated DC Power Supplies: Linear and Switching.
Linear power supplies can never output a higher voltage than the input source. In theory, a linear power supply that is driven by typical 110V wall outlet could only output 110V, assuming the device were 100% efficient. Realistically, no power supply is 100% efficient because power conversion always results in energy loss, usually in the form of heat dissipation. Therefore, linear power supplies usually output voltage that is significantly less than the input.
Switching power supplies can step-up, step-down or invert the input voltage. Switching power supplies are usually larger, noisier and more expensive than their linear counterparts, however, switching power supplies are typically more efficient.
Choosing the right DC power supply for your application requires definition of some basic design specifications: voltage range, current range, number of outputs, power cleanliness (known as “ripple”) and programmability. In general, the higher the output voltage and the lower the ripple, the more expensive the DC Power Supply. Multiple outputs and programmability features will also add to the cost.
The least expensive DC Power Supplies are ideal for electronics hobbyists and basic electro-mechanical applications where only raw power is required. It is likely that the devices being powered in these applications already have power-conditioning features that eliminate the need for precision input power. Low power, single output, DC power supplies range in price from $50 to $200.
Mid-range power supplies are best suited for non-critical, laboratory projects involving more advanced electro-mechanical applications or basic board-level testing. Mid-range power supplies might have multiple outputs, higher power ratings, lower ripple and precision, digital metering (+/- .001V, +/- .01A). Mid-range DC power supplies can be linear or switching and could range in price from $200 to $1,000.
High-end applications requiring high output voltage, advanced programmability (GPIB PC Interfaces), numerous outputs and very low ripple should budget in excess of $1,000 for their DC power supply. Many laboratory, R&D and testing applications could easily spend $5,000 to $10,000 per power supply.
This article has introduced some basic features and applications of DC Power Supplies. Before making your final purchase, be sure to consult the manufacturer and thoroughly understand all the specifications of a particular product. Choosing the best and most economical DC Power Supply for your application does not have to be a complex and time-consuming task. By identifying your design parameters, you will quickly narrow down product selection to niche class of products from only a few manufacturers.
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Selasa, 06 Juli 2010
Sabtu, 05 Juni 2010
Buying Used Electronic Test Equipment… What's The Difference Between Used, Refurbished, Remarketed And Rebuilt?
According to the research firm Frost & Sullivan, the estimated size of the North American used test and measurement equipment market was $446.4 million in 2004 and is estimated to grow to $654.5 million by 2011. For over 50 years, companies and governments have procured used test and measurement instruments in order to realize a number of benefits including the need to:
- reduce equipment acquisition costs,
- replace discontinued testing instruments,
- circumvent lengthy new product delivery times, and
- conform to legacy standards and specifications.
Although there are many considerations when purchasing used test and measurement instruments, the quality of the instrument and reliability of the vendor should be at the top of the list. Used test equipment vendors deploy a number of bywords that represent the equipment they sell, including "refurbished", "remarketed", "reconditioned", "rebuilt" and, the obvious, "used". These marketing adjectives typically imply various quality processes and buyers of used test equipment should execute their due diligence prior to purchasing.
"Used" or "Remarketed" equipment often describes products sold with an "as-is" supposition. You might purchase used equipment from an end-user organization or auction company that is selling surplus assets. Products sold as "used" should be priced at the lower scale of the market spectrum and it is not uncommon for quality issues to arise with "used" equipment. It is likely that the instruments have not been tested and have an uncertain history. It is only prudent to purchase "Used" equipment if you have the in-house repair and calibration facilities/expertise and are able to procure the item at a cost low enough that the added expense of repair and calibration remains to be a positive, economical outcome.
"Refurbished and Reconditioned" are akin and are the most common presentment of used equipment from equipment dealers. Refurbished equipment is fully tested and calibrated to NIST standards to assure that they meet the original manufacturers' specifications. Refurbished equipment should come with all standard accessories and operating manuals. Malfunctioning internal components will have been replaced or repaired and the product will have been cosmetically cared for including painting and the replacing of face plates, button and knobs. Refurbished equipment is typically sold with a 30-90 day parts/labor warranty and is priced in the middle to high-end of the market spectrum.
Finally, some vendors advertised "Rebuilt" test equipment. Many instrument options are field-installable and can be built-to-order according to the customer's requirements. Some products can even be converted from one generation or version to the next by adding various components. There is absolutely nothing wrong with purchasing rebuilt equipment and, in fact, if you can not find the exact product configuration you are sourcing, you should ask qualified vendors about the possibility adding those options. As with used and refurbished equipment, always exercise caution in choosing a vendor. Assure that the vendor is qualified or uses a qualified electronics laboratory to repair, calibrate and rebuild the products you seek.
Purchasing used, refurbished or rebuilt electronic test equipment is a great way for organizations to save 30-70% on their asset acquisition costs. Warranties and guarantees from used test equipment vendors are formidable. In select product groups, the original equipment manufacturers offer extended warranties in partnership with the vendors that are the selling those products.
Exercise caution and perform due diligence on your vendors. It is most effective to first identify a qualified used equipment vendor and begin a supplier relationship, as opposed to sourcing each instrument you need individually. If your qualified vendor does not have what you are looking for in inventory, it is likely that they will be able to locate it within 24 hours. By first identifying and working with a select few vendors, you will assure consistent quality and economical pricing with every used test equipment purchase.
- reduce equipment acquisition costs,
- replace discontinued testing instruments,
- circumvent lengthy new product delivery times, and
- conform to legacy standards and specifications.
Although there are many considerations when purchasing used test and measurement instruments, the quality of the instrument and reliability of the vendor should be at the top of the list. Used test equipment vendors deploy a number of bywords that represent the equipment they sell, including "refurbished", "remarketed", "reconditioned", "rebuilt" and, the obvious, "used". These marketing adjectives typically imply various quality processes and buyers of used test equipment should execute their due diligence prior to purchasing.
"Used" or "Remarketed" equipment often describes products sold with an "as-is" supposition. You might purchase used equipment from an end-user organization or auction company that is selling surplus assets. Products sold as "used" should be priced at the lower scale of the market spectrum and it is not uncommon for quality issues to arise with "used" equipment. It is likely that the instruments have not been tested and have an uncertain history. It is only prudent to purchase "Used" equipment if you have the in-house repair and calibration facilities/expertise and are able to procure the item at a cost low enough that the added expense of repair and calibration remains to be a positive, economical outcome.
"Refurbished and Reconditioned" are akin and are the most common presentment of used equipment from equipment dealers. Refurbished equipment is fully tested and calibrated to NIST standards to assure that they meet the original manufacturers' specifications. Refurbished equipment should come with all standard accessories and operating manuals. Malfunctioning internal components will have been replaced or repaired and the product will have been cosmetically cared for including painting and the replacing of face plates, button and knobs. Refurbished equipment is typically sold with a 30-90 day parts/labor warranty and is priced in the middle to high-end of the market spectrum.
Finally, some vendors advertised "Rebuilt" test equipment. Many instrument options are field-installable and can be built-to-order according to the customer's requirements. Some products can even be converted from one generation or version to the next by adding various components. There is absolutely nothing wrong with purchasing rebuilt equipment and, in fact, if you can not find the exact product configuration you are sourcing, you should ask qualified vendors about the possibility adding those options. As with used and refurbished equipment, always exercise caution in choosing a vendor. Assure that the vendor is qualified or uses a qualified electronics laboratory to repair, calibrate and rebuild the products you seek.
Purchasing used, refurbished or rebuilt electronic test equipment is a great way for organizations to save 30-70% on their asset acquisition costs. Warranties and guarantees from used test equipment vendors are formidable. In select product groups, the original equipment manufacturers offer extended warranties in partnership with the vendors that are the selling those products.
Exercise caution and perform due diligence on your vendors. It is most effective to first identify a qualified used equipment vendor and begin a supplier relationship, as opposed to sourcing each instrument you need individually. If your qualified vendor does not have what you are looking for in inventory, it is likely that they will be able to locate it within 24 hours. By first identifying and working with a select few vendors, you will assure consistent quality and economical pricing with every used test equipment purchase.
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