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.

Output of Electronic Muscle Stimulators: Physical Therapy and Police Models Compared.

INTRODUCTION: Both physical therapists and police officers use electrical muscle stimulation. The typical physical therapist unit is attached with adhesive patches while the police models use needle-based electrodes to penetrate clothing. There have been very few papers describing the outputs of these physical therapy EMS (electrical muscle stimulator) units. METHODS: We purchased 6 TENS/EMS units at retail and tested them with loads of 500 Ω, 2 kΩ, and 10 kΩ. RESULTS: For the typical impedance of 500 Ω, the EMS units delivered the most current followed by the electrical weapons; TENS units delivered the least current. At higher im-pedances (> 2 kΩ) the electrical weapons delivered more current than the EMS units, which is explained by the higher voltage-compliance of their circuits. Some multi channel EMS units deliver more calculated muscle stimula tion than the multi-channel weapons. CONCLUSION: Present therapeutic electrical muscle stimula-tors can deliver more current than present law-enforcement muscle stimulators.

Electrical Weapon Charge Delivery With Arcing.

INTRODUCTION: Human electronic control with the Conducted Electrical Weapon (CEW) has gained widespread acceptance as the preferred law enforcement force option technology due to its dramatic injury and fatal shooting reduction. However, with bulky or baggy clothing, a CEW probe may fail to make direct skin contact and thus arcing is critical to complete the circuit. The goal of the study was to evaluate the ability of modern CEWs to deliver their pulse charges across typical required arcing distances. METHODS: Popular TASER® CEW models X26E (openloop output), and the X2 and X26P (with closed-loop outputs) were activated using a cartridge connected to a custom polymer air-gap fixture. For each model 5 units were tested. The raw and normalized charge delivery were evaluated according to ANSI-CPLSO-17. RESULTS: All 5 units of each model satisfied ANSICPLSO-17 even at maximum arcing length. The X26P CEW had the greatest arcing gap capability. CONCLUSIONS: The stabilized closed-loop charge output feedback of modern electrical weapons (X2 and X26P CEWs) provides a significantly improved output consistency under arcing conditions. With arc lengths of 10-20 mm per probe, the X2 CEW normalized output charge exceeds that of some units of the older higher output X26E CEW model.