The G-sensor is the component that turns a passive recording device into an active safety tool. Without it, your dash cam is a camera that records everything continuously with no way to distinguish a routine commute from a collision. With it, the camera identifies significant events automatically and protects the relevant footage from being overwritten.
Here's how it works, why sensitivity matters, and how to calibrate it correctly for your specific vehicle and driving environment.
What a G-Sensor Is
A G-sensor (gravitational sensor) is a three-axis accelerometer — a microelectromechanical system (MEMS) that measures acceleration forces in three dimensions: forward/backward, left/right, and up/down. Each axis is measured independently and continuously.
In normal driving, the accelerometer reads near 1g downward (gravity), with small positive and negative deviations as the car accelerates, brakes, and corners. When a significant event occurs — hard braking, a side impact, a rear-end collision — the accelerometer detects a force spike that exceeds the normal range and triggers the event recording protocol.
What Happens When the G-Sensor Triggers
When the G-sensor detects a force above the trigger threshold:
- The current recording file is immediately locked — flagged as an event file and excluded from the loop overwrite cycle.
- The camera continues recording for a set post-event period (typically 30–60 seconds, depending on settings).
- The event is logged with a timestamp and, if GPS is active, GPS coordinates.
- If the camera is cloud-connected, the event clip is queued for priority upload.
- A notification is sent to the paired app.
The result: the footage from before, during, and after the trigger event is preserved regardless of what happens to the loop recording afterward.
Pre-Event Recording
Most cameras don't start recording at the moment the G-sensor triggers — they've been recording continuously all along. The G-sensor trigger determines which portion of the continuous recording is saved and protected.
The standard event clip includes a pre-trigger buffer — footage from before the event, typically 10–30 seconds — plus the post-trigger footage. This pre-event footage is often the most valuable part: it shows the approach to the incident, the following distance, the speed, and the other vehicles' behavior before the collision occurred.
G-Sensor Sensitivity Settings
This is where most users make mistakes. G-sensor sensitivity determines the force threshold that triggers an event. It's typically adjustable in the app or camera settings on a scale of Low / Medium / High (or a numeric scale of 1–10).
Too high (over-sensitive): The camera triggers on potholes, speed bumps, rail crossings, and rough road surfaces. Your event log fills with false triggers, real events are harder to find, and the SD card and cloud storage fill with routine events. Parking mode generates alerts every time a large truck drives past.
Too low (under-sensitive): Minor accidents don't trigger the event protocol. A low-speed rear-end collision or a side-swipe might not generate a locked event file — the footage may still exist in the loop recording, but it could be overwritten before you realize it's needed.
Medium (default recommendation): The default setting on most cameras is medium sensitivity. This is appropriate for smooth highways and standard urban driving. Adjust based on your specific experience — if you get multiple false triggers per week, lower sensitivity; if you've had an incident that wasn't captured as an event, raise it.
Calibrating for Your Vehicle
Different vehicles transmit different baseline vibration levels to the camera mount. A diesel truck transmits more engine vibration than a hybrid sedan. A lifted 4x4 on a gravel road generates more random acceleration events than a low-profile car on smooth pavement.
The auto-calibration function (available in Nexar and several other cameras via the app's Settings → Camera → Calibrate) establishes a vehicle-specific baseline by sampling accelerometer data during normal driving. Subsequent event triggers are relative to this baseline, not to a fixed universal threshold. Run calibration after installation and again if you change vehicles or mount positions.
Parking Mode G-Sensor vs. Motion Detection
Parking mode typically uses both the G-sensor (for impact triggers) and motion detection (for visual movement triggers). These are separate systems:
- G-sensor in parking mode: Detects physical impacts — someone hitting your bumper, rocking the car, or breaking into it with force. Highly reliable for actual physical events. Won't trigger on a car driving past without touching yours.
- Motion detection in parking mode: Detects changes in the camera's field of view — movement of objects within the frame. Captures approaching vehicles, people walking toward the car, and visual events that don't involve physical contact. More prone to false triggers from wind, changing light conditions, and distant motion.
The combination of both in parking mode provides the most comprehensive coverage. The G-sensor catches physical events; motion detection catches approach events before physical contact occurs.
G-Sensor Data in Insurance Claims
The G-sensor event log provides evidence independent of video footage. When an event triggers, the acceleration force magnitude (in g-force) is recorded — this establishes the severity of the physical event at the moment of impact.
In accident reconstruction, G-sensor magnitude data helps establish:
- Whether the impact was consistent with the claimed damage (a 15mph rear impact generates a different G-force signature than a 45mph rear impact)
- The direction of the primary force (which axis registered the highest peak identifies the angle of impact)
- The timing and sequence of multiple impacts in a multi-vehicle event
This data is embedded in the event file metadata. A forensic analysis of the raw sensor data from your camera provides an objective force measurement that complements the visual evidence from the video.
Common G-Sensor Questions
Can I disable the G-sensor? Yes, in most cameras, though this removes event locking entirely. Not recommended except in specific research or testing scenarios.
Will the G-sensor trigger on a car wash? Car wash vibration and water pressure can trigger G-sensor events. Some cameras have a car wash mode that temporarily disables the trigger. If yours doesn't, expect a few false event files from car wash visits.
What happens if the G-sensor fails? The camera continues recording normally — the G-sensor is not required for recording. Only event locking is lost. If you suspect G-sensor failure (no events triggering even in clear impact situations), check firmware and run calibration. If the issue persists, contact support.