Diagnostic Imaging Ultrasound systems continue to become more technologically sophisticated, taking advantage of embedded operating systems, faster processors and increased RAM capacities. These advances allow for faster and wider image data processing, 3D/4D imaging, better noise canceling algorithms and enhanced diagnostic tools. Most of these new Ultrasound platforms are dependent on information stored on hard drives, magneto optical drives, CD/DVD drives and network drives.

One of the by-products of this rapid increase in complexity has been a drastic increase in data corruption, system lock-ups and general operational abnormalities. Power failures, sags, surges, and line noise wreck havoc. These problems are worst during transitional weather periods. The onset of Summer is heralded by an avalanche of air conditioning system coming on line. The beginning of Winter is marked by millions of heaters cycling on. Manufacturers now recommend the use of a UPS with most new Ultrasound systems to provide better uptime and to protect the customer's investment.

Where do you start?

The first question would be what is a UPS?

Federal Standard FED-STD-1037C, published August 7, 1996 defines a UPS as:

?Uninterruptible power supply (UPS): A device that is inserted between a primary power source, such as a commercial utility, and the primary power input of equipment to be protected, e.g., a computer system, for the purpose of eliminating the effects of transient anomalies or temporary outages. Note 1: A UPS consists of an inverter, usually electronic, that is powered by a battery that is kept trickle-charged by rectified ac from the incoming power line fed by the utility. In the event of an interruption, the battery takes over without the loss of even a fraction of a cycle in the ac output of the UPS. The battery also provides protection against transients. The duration of the longest outage for which protection is ensured depends on the battery capacity, and to a certain degree, on the rate at which the battery is drained.?

What common problems does a UPS address?

A UPS may be used to correct the following problems:

1.Power Failure -Total loss of line or power utility (PG&E)

2.Power Sag-Short duration under-voltage condition

3.Cycle Loss-Loss individual AC cycles

4.Power Spike (Surge)-Short duration over-voltage condition

5.Brownout-Extended duration low line voltage

6.Over-voltage-Extended duration high line voltage

7.Line noise-Noise superimposed on the power waveform

8.Frequency-Variations in power waveform frequency

9.Switching transient-Under or Over-voltage for a few nanoseconds

10.Harmonic Distortion-Multiples of the power frequency superimposed on the power waveform

Are there different kinds of UPS's?

The most common types of UPS's we encounter are:

The Offline or Standby UPS passes power through to the load until a power failure, sag or spike occurs. At that point the UPS switches the load from the primary or utility power to its battery powered inverter. Though the transition results in only a small delay in the restoration of power it has the potential of causing catastrophic system failures. Once the utility power has returned to normal for a predefined period of time the UPS will switch the load back, an additional transition that can create system issues. This design only charges when the power utility is available. It typically has a modified square wave output and is designed for 600VA or less. Though cost effective it will not address most of the power problems listed previously.

The Inline UPS is the best candidate for use with your Ultrasound system. The inline UPS, also called a dual-conversion or double-conversion UPS, isolates the load from the power utility. The Inline uninterruptible power supplies operate by converting incoming utility AC power to DC and then convert the DC back to AC to power the connected equipment. This design isolates the load from the incoming power and generates the sinusoidal output. These UPS's address all our power concerns and allow for the use of almost any incoming power. Most Inline UPS units have a monitoring system on the output that senses when the voltage or current goes out of specification; a bypass is then activated to shunt incoming AC directly to the attached load without interruption.

What if my system has an internal UPS?

The internal UPS provides power to allow the systems CPU's time to perform an orderly shutdown. These devices are not nearly large enough to supply the needs of your entire system they provide your system the time needed to save pointer, close files and park disk drives.

If I have and internal UPS why add an Inline UPS?

Your Inline UPS corrects the power issues we discussed earlier and it also provides time for the system operator to save and close studies that may be in progress. This additional time will help prevent the corruption of patient data and the possible loss of access to your patient archive. These are high level functions not protected by the internal UPS.

Choosing a UPS.

You will need to know how much power your system requires. This will be specified in VA or wattage, both are numbers representing the output ratings of the UPS. A good rule of thumb for selecting a UPS is 80% of the UPS capacity. This will allow for loss due to conversion and allow for start-up current, unfortunately nothing is free.

?The VA rating is the apparent power, while the Watt rating is the real power (or true power). The difference between these two numbers is the reactive power. Reactive power arises due to the effects of capacitance and inductance of components in the load to be powered by the AC circuit. In a purely resistive load the apparent power is equal to the true power and the amount of VA's and Watts used would be equivalent. However, in more complex loads, such as computers the apparent power used (VA's) will be larger than the true power used (watts). The ratio of this difference is called the power factor.? Wikipedia

Be sure to ask what input power will be required. Your system may be happy with a 15amp outlet but the UPS may need a 20amp supply. That additional 20% capacity may push you input current up to the next breaker size.

What about maintenance?

Most UPS units require little maintenance. They should be clean and free from debris. This type of UPS is heavy and tends to disappear under a table or in a corner. They must have adequate airflow.

These units usually have resident self-testing which will warn the operators if there are circuit faults, internal failures and battery issues. Their batteries are typically sealed gel cells and are functional for 5 or more years. They should be replaced and disposed of in accordance with manufacturers? recommendations, local and federal laws.