Hotstick Reveals High Voltage Detector For First Responders

JUN 29 2018 BY MARK KANE 7

The growing number of plug-in electric cars, and also hybrids, as well as expanding solar market, leads to the topic of how emergency responders will be able to detect high DC voltage.

The DC hotstick voltage probe can accurately detect the presence of DC voltages in a hybrid electric vehicle. Credit: Carlos Jones/Oak Ridge National Laboratory, U.S. Dept. of Energy.

One of the recent Tesla accidents raised questions of how to deal with an energized battery when the mechanism for neutralizing it — the “cut loop” — is destroyed.

Hotstick USA exclusively licenses a direct-current detector developed by the Department of Energy’s Oak Ridge National Laboratory to offer it emergency responders.

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Checking the voltage will let responders know what action should be performed.

Nance Ericson, left, and Bruce Warmack of ORNL test the DC hotstick on a hybrid electric vehicle. Credit: Carlos Jones/Oak Ridge National Laboratory, U.S. Dept. of Energy

“In emergency situations, first response teams often rely on voltage detectors such as Hotstick USA’s flagship product, the AC Hotstick, to sense the presence of dangerously high alternating current, or AC, electric voltages from a safe distance. The increase in electric vehicles on the road and solar panels on homes means high voltages could also originate from direct current, or DC, sources not accurately detected by existing technologies.

ORNL inventors Bruce Warmack and Nance Ericson, who specialize in experimental physics and sensing technologies, worked with Hotstick USA to develop a DC-detection prototype.”

“The DC hotstick prototype is a handheld device equipped with easy-to-read indicator lights that show whether the probe has established a connection and whether the electricity source is hot. In a crash involving an electric vehicle, for instance, the car’s battery could still be connected and energized at a deadly 400 to 600 volts.

The probe is designed with a novel piercing tool to cut through plastic cable insulation that may obstruct contact with the vehicle’s battery and to indicate that a valid electrical connection is made. “This ensures good contact for an accurate voltage reading in a situation where decisions must be made in seconds,” Warmack said.

Early results from field testing of the patent-pending technology have yielded a positive response, according to Warmack. He and his team plan to expand the functionality of the hotstick including collecting, sharing and storing voltage data.

After further development, Beckmann expects the DC hotstick to complement the company’s existing AC sensing technology, which is the market leading device, and satisfy the need expressed by many customers.”

“Inventors of this technology include ORNL’s Warmack, Ericson, Yarom Polsky and Roger Kisner.

The direct current voltage probe was designed under the sponsorship of the U.S. Fire Administration, a division of the U.S. Department of Homeland Security.

UT-Battelle manages ORNL for DOE’s Office of Science. The Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit”

William Beckmann, president of Hotstick USA said:

“Emergency responders need to assess their safety before commencing rescue efforts. The DC hotstick detector will help them more accurately determine whether an electric vehicle or home is energized from a direct-current source for better, safer emergency assessments.”

“This new tool protects them as they’re protecting others and saving lives,” he added.

Richard Raines, director of ORNL’s Electrical and Electronics Systems Research Division said:

“Our partnership with Hotstick USA exemplifies how our nation’s critically needed capabilities can be conceptualized, incubated and prototyped at the lab and then transitioned to industry for commercialization. This effort demonstrates the successes possible through strong, collaborative laboratory-industry partnerships.”

The DC hotstick voltage probe can accurately detect the presence of DC voltages in a hybrid electric vehicle. Credit: Carlos Jones/Oak Ridge National Laboratory, U.S. Dept. of Energy.

Bonus: How the AC Hotstick USA works

source: ORNL

Categories: General


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7 Comments on "Hotstick Reveals High Voltage Detector For First Responders"

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“…the mechanism for neutralizing it — the “cut loop” — is destroyed.”

i thought this to be self-evident, but if the “cut loop” is destroyed, doesn’t that mean the loop is indeed cut? After all, the loop is not only “cut” but it has been “destroyed.”

The cut loop is a design feature allowing first responders to open all circuits from the batteries of the vehicle by cutting in a designated place on the vehicle. If crash damage has rendered the point inaccessible, or if fault from overcurrent/ fire damage has welded/shorted the cut loop solid, then the vehicle will remain energized.
“IEC Definition
The International Electrotechnical Commission (IEC) defines supply system low voltage as voltage in the range 50 to 1000 V AC or 120 to 1500 V DC.
In electrical power systems low voltage most commonly refers to the mains voltages as used by domestic and light industrial and commercial consumers. “Low voltage” in this context still presents a risk of electric shock, but only a minor risk of electric arcs through the air.”

At first I was wondering about that article because none of the EVs I know has high-voltage batteries…

And was is the really new with that product? There’re now already for decades devices (sometimes even offered by supermarkets) which can detect wires under voltages in a wall…


Non contact voltage meters use induction to detect or measure voltage. There are many varieties, with Klein making a very nice one that will read and indicate level from 24VAC to 1000VAC clearly and safely. For transmission lines, more robust detectors, and the resistive handles to get the probe near the conductor, are made by Hot Stick. AC clamp meters use this same field to measure current without contacting energized cobductors. DC doesn’t have the same inductive field, due to its zero frequency. Hall effect sensors have been getting better, allowing DC current to be measured through a magnetic field, but they are more range specific, and obviously wouldn’t work on an open circuit with potential present, but no current flow. It is likely that Hall effect sensors were employed in this new meter, allowing for resistive isolation between the probes, metering, and handle. This would also help to protect the user in the event that the probes inadvertently discharge capacitors, or cross inverted AC transformers or components.

Context, I guess? The traction battery (typically 250 – 380 V), and everything connected to it (indicated by orange wires), is called “high voltage”, as opposed to the traditional 12 V system. The voltage is high enough to be deadly; so to first responders, that certainly qualifies as “high voltage”…

(That’s purportedly the main selling point of mild hybrids: 48 V is safe enough not to need costly special precautions.)

I hope those LEDs are visible in full daylight.

“we charged this line to 120 Volts of AC current…”
This product looks handy, but somewhere there’s a disconnect between the folks established in “experimental physics” and the video describing its AC Hotstick product. There are multiple descriptions of current levels expressed in voltage, while what the product aims to detect is actually the absence of current in a situation with the potential for current to become hazardously realized…