Estimation of Physiological Impedance from Neuromuscular Pulse Data.

INTRODUCTION: A Conducted Electrical Weapon (CEW) deploys 2, or more, probes to conduct current via the body to induce motor-nerve mediated muscle contractions, but the inter-probe resistances can vary and this can affect charge delivery. For this reason, newer generation CEWs such as the TASER® X3, X2 and X26P models have feed-forward control circuits to keep the delivered charge constant regardless of impedance. Our main goal was to explore the load limits for this "charge metering" system. A secondary goal was to evaluate the reliability of the "Pulse Log" stored data to estimate the load resistance. METHODS: We tested 10 units each of the X2 (double shot), X26P, and X26P+ (single-shot) CEW models. We used non-inductive high-voltage resistor assemblies of 50, 200, 400, 600, 1k, 2.5k, 3.5k, 5k, and 10k Ω, a shorted output (nominal 0 Ω), and arcing open-circuits. The Pulse Log data were downloaded to provide the charge value and stimulation and arc voltages for each of the pulses in a 5 s standard discharge cycle. RESULTS: The average reported raw charge was 65.4 ± 0.2 µC for load resistances < 1 kΩ consistent with specifications for the operation of the feed-forward design. At load resistances ≥ 1 kΩ, the raw charge decreased with increasing load values. Analyses of the Pulse Logs, using a 2-piece multiple regression model, were used to predict all resistances. For the resistance range of 0 - 1 kΩ the average error was 53 Ω; for 1 kΩ - 10 kΩ it was 16%. Muzzle arcing can be detected with a model combining parameter variability and arcing voltage. CONCLUSIONS: The X2, X26P, and X26P+ electrical weapons deliver an average charge of 65 µC with a load resistance < 1 kΩ. For loads ≥ 1 kΩ, the metered charge decreased with increasing loads. The stored pulse-log data for the delivered charge and arc voltage allowed for methodologically-reliable forensic analysis of the load resistance with useful accuracy.

Detection of Arcing and High Impedance with Electrical Weapons.

INTRODUCTION: Conducted electrical weapons are primarily designed to stop subjects from endangering themselves or others by deploying 2, or more, probes to conduct current via the body to induce motor-nerve mediated muscle contractions, but probe impedance can vary significantly including open circuits from probes failing to complete or maintain a circuit. METHODS: We tested 10 units of the TASER® 7 model with a range of impedances and open circuit conditions. Pulse data (stored in the device's memory) were used to predict the load resistances and detect arcing conditions. Acoustical data (recorded externally) was evaluated on an exploratory basis as a secondary goal. RESULTS: The average error of predicted resistance, over the physiological load range of 400-1000 Ω, was 8%. Arcing conditions was predicted with an accuracy of 97%. An arcing condition increases the duration of the sound generation. CONCLUSIONS: The TASER 7 electronic control device stored pulse-log data for charge and arc voltage yielded forensic analysis of the load resistance with reliable accuracy.