Why An Isolation Transformer Is Critical In Lab Environments: A TEST CASE December 11 2016, 0 Comments
In a lab at Providence Medical Center, an uninterrutible power supply (UPS) connected to a stand alone isolation transformer sits next to every lab instrument and lab computer. The 2 part combination provides clean uninterrupted power to the lab's flow cytometers, computers, and other instruments. Among the numerous instruments and computers are a BD LSRII, a Fortessa LSR, and an Aria II.
Why incur the expense of adding an isolation transformer to an existing UPS or purchasing a UPS with a built in isolation transformer?
The reason is that the laboratory technicians were experiencing “video camera noise on the internal Accudrop camera when the high density filter was in place…slow moving wave forms like snow on old style B&W TVs which were rendering the Accudrop algorithm useless.” Using a UPS by itself did not resolve this particular issue.
Battery Backup Power, Inc. diagnosed this quickly as electrical noise/feedback caused by other equipment operating in the facility. The issue was resolved with a separate isolation transformer installed before the uninterruptible power supply (UPS) and laboratory instruments.
A little background on interference:
Laboratory instruments and any sensitive electronic device can be degraded by electronic noise (radio frequency interference, called RFI). Medical centers, labs, data centers, offices, and even homes are full of potential interference sources, such as computer power supplies, wall wart AC adapters such as those on modems/routers, fluorescent light bulbs, light dimmers, laser printers, microwaves, etc.
In this case, the power supply interference of some other electrical device on the same circuit appeared as a faint horizontal band that moved slowly down (can also move up) the screen. This is typically referred to as the 60 Hz traveling wave. The traveling wave indicates that there is an inadequate amount of external filtering (no isolation transformer) or a potential filtering problem inside the instrument's power supply. A 60 Hz AC signal enters the electrical circuit that the instrument is plugged into and conflicts with another 60 Hz signal.
Since many outlets are on the same circuit, interference or voltage spikes/drops can enter the circuit from any device plugged into any outlet on that circuit. This is why your office lights may dim when you start to print something on a laser printer. The laser printer (if on the same circuit as the office lights) reduces the overall voltage on the circuit momentarily dimming the lights.
Back to Providence Medical Center and lab instruments:
After the recommended addition of a stand alone isolation transformer, Providence Medical Center’s Laboratory Manager stated, “Everything is working brilliantly!”
The Manager of Flow Cytometry at Providence Medical Center commented, “I was running instrument calibration and plugged and unplugged the Battery Backup unit several times for several minutes at a time…It performed very well, switching itself to battery power without causing any surges, or interference…Calibration of the instrument runs perfectly normally.”
“Flow cytometry is a technology that is used to analyze the physical and chemical characteristics of particles in a fluid as it passes through at least one laser. Cell components are fluorescently labelled and then excited by the laser to emit light at varying wavelengths.”
Uninterruptible Power Supply Pictured Above: http://www.backupbatterypower.com/collections/frontpage/products/1-5kva-double-conversion-battery-backup-power-ups
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