Smith Research & Technology, Inc.
Colorado Springs, Colo.

The following is a list of the most desirable characteristics for any inductive alternating-current sensor.

• High gain at low currents (gain depends on the number of turns and core permeability).
• Wide operating range without saturation (at which point the computer control ceases to function because the output no longer changes with an input change). A proprietary technology that acts like a magnetic air-gap is used to achieve this.
• Mitigation (smoothing) of the drastic knee (saturation point) that causes spikes in a toroid (even at light loading) at flux reversal. The air-gap assists in this also.
• Ability to operate several times above the rated current without damage to the sensor.
• A floating, isolated output to avoid signal mixing. This trait applies to toroid and SRT devices, but may not be available in other types of inductive devices.
• High linearity at unloaded (open circuits) operation to keep power dissipation low. (CTs and toroids are operated with significant current - i.e., they suffer a "burden")
• Ability to measure current by measuring the flux that surrounds the wire being monitored, eliminating the need for an auxiliary power source just to measure current (as is needed in hall-effect devices).
• Ability to cover a wide range of frequencies. Our standard products are available from 6 Hz to 14 MHz, but we can go higher if needed.
• Ability to cover a wide range of temperatures (depends on potting). Most of our devices have been tested from 80 degrees C to -5 degrees C, but lower or higher temperatures may be available.
• Packaged for the convenience of the user. A sensor that will allow operation up to several thousand volts on the line or wire being monitored, with no dangerous shocks from the output.
• Voltage output repeatability at identical currents.