Protect Expensive Mechanical Equipment with our Self-Calibrating Current Switch

September 4, 2019
Tech Tuesday

Most people are aware that Functional Devices, Inc. sells currents switches with a few variations, like solid core vs split core, fixed vs adjustable threshold, and wires vs terminals. However, there is one of our current switches that I doubt as many people know about. It is the Self-Calibrating Current Switch.

The Self-Calibrating Current Switch is unique among our offerings and is available in two models, RIBXGA-SCAL (wires for field connection) and RIBXGTA-SCAL (terminal for field connection). Most of our current switches have a normally open (NO) output that closes when the current through the core exceeds the threshold, but the output of the self-calibrating version (-SCAL) is only closed when the current sensed is within a selectable range above and below the threshold. Also, as the name suggests, the -SCAL unit calibrates itself and sets the threshold to the nominal current of the load.

To set the threshold, the current switch is clamped around one of the conductors to the load. When current flows through the conductor for the first time, the -SCAL unit begins its calibration process, which lasts for 30 seconds. After that time, the threshold is set at that nominal current. A DIP switch on the unit allows for re-calibration at any time, and a second DIP switch is used to set the threshold differential. The differential is the percentage of current above and below the nominal current that defines the range where the current switch is closed. This range can be set to ±15% or ±25%. For example: If the nominal current of the load is 100 Amps, and the differential is set to ±25%, the output of the current switch would be closed from 75 – 125 Amps.

Having a current switch that is only closed within a range of the nominal current is beneficial in many applications, and it can be used to help protect expensive mechanical equipment. The main application is to sense current to a motor, where a current below the range could indicate a belt loss scenario, and a current above the range could indicate a locked rotor scenario. Both states could be detrimental to the equipment, and the addition of the -SCAL unit could alert maintenance of such a situation or be used to shut the equipment down completely.

If you would like more information about our Self-Calibrating Current Switch, read through the datasheet or give us a call here and we will answer your questions.

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About the Author

Henry Smith is a design engineer at Functional Devices, Inc. He has a BS EET obtained from Purdue University in 2014 and a lifelong interest in electronics. As an engineer at Functional Devices, he gets to provide Technical Support to our customers, from distributors to specifying engineers and installers.

Henry enjoys providing tech support, as it allows our company to assist at every level of our product’s lifecycle and exposes us to interesting and unique applications. While not every technical question is unique, even answering a simple question or providing someone with the information in a timely manner can go a long way to helping him or her meet a deadline.