Anti-collision is the quiet safety system that makes a height adjustable desk fit real life. When a surface moves dozens of times a day, it will eventually meet a chair arm, a wall, a drawer, or someone’s knees. A good system recognizes resistance early, stops smoothly, and backs away without drama. A weak one misses soft obstacles, triggers false alarms, or jerks hard enough to spill a drink. Here’s how anti-collision actually works inside a sit stand desk, what affects sensitivity, and how to test and tune it so the setup stays safe, quiet, and reliable.

How systems sense a collision

Most desks use one of three approaches, and the best pair them in a hybrid design.

• Motor-current sensing: The control box monitors current draw from each linear actuator. A sudden spike suggests resistance, so the controller stops and reverses slightly. It’s simple and cost-effective, but soft obstacles can soak up force without causing a sharp spike.

• Position error via hall sensors: Each motor in a lifting column reports rotation. If columns desynchronize under load, the controller infers an obstruction or bind and halts motion. This is great for tilt and jam detection, especially on three-leg frames.

• IMU-assisted (accelerometer/gyro): Premium systems add motion sensors to detect tiny shocks or tilt changes as soon as the desk meets an obstacle. IMUs improve upward detection (hitting shelves) and soft-object sensitivity.

What changes sensitivity in the real world

Anti-collision is not a fixed number. It’s influenced by mechanics, load, and even temperature.

• Surface mass and load distribution: Heavier tops and gear raise baseline current. A desktop with most weight on one side increases friction in that column, reducing margin for detection.

• Speed and ramps: Faster lift speeds create higher kinetic energy before the stop. Smooth start/stop ramps minimize “thumps” but also shape how quickly the controller recognizes resistance.

• Column overlap: At maximum height, lifting columns have less telescoping overlap. Slight wobble or friction changes can look like resistance. A rigid frame with long feet and a reinforced crossbar helps.

• Cable drag: Tight cables, a crowded cable tray, or a vertical cable chain with too little slack can trip anti-collision going up or down.

• Temperature and duty cycle: Warm motors after many cycles may run different current profiles. Give the system its rated cool-down time.

Upward vs. downward protection

Good systems protect in both directions. Downward is about knees, drawers, and chair arms. Upward is about shelves, wall art, or a window ledge. Upward protection is harder because the structure compresses less and “gives” less, so IMU assistance or tighter current thresholds help.

How to calibrate and set sensitivity
Always start with a clean baseline so the control box “knows” the desk’s natural motion.

• Run a full reset: Clear the area. Hold the down button on the desk controller to drive the desk to its lowest mechanical stop. Keep holding until the controller beeps or shows a reset code, then release.

• Set sensitivity: If your control box offers levels (for example, 1–5), start at the default. In busy shared spaces, go one step more sensitive for downward moves.

• Test under load: Calibrate with the real desktop, monitors, and cable management installed. Recalibrate if you add heavy gear.

Real-world tests you should run
Never test with body parts. Use safe, repeatable props.

• Downward knee zone test: Place a 50 to 75 mm thick foam block or a rolled towel on a chair where knees would be. Lower the desk. It should stop promptly and reverse a few millimeters without crushing the foam.

• Upward shelf test: Place a felt-padded board or thick book under a fixed shelf above the desk. Raise the desk until it contacts the pad. It should stop and back off cleanly.

• Drawer and CPU holder check: Open a shallow drawer 25 mm and lower the desk. Confirm a stop before contact. If you use a CPU holder, ensure it clears crossbars at all heights.

• Cable chain sweep: Move from lowest to highest while watching the vertical cable chain. If it straightens tight at any point, reintroduce slack or lengthen the chain.

• Corner tilt test on three-leg frames: With an L-shaped desk, put a foam block near the inside corner. Raise and lower; the system should detect slight tilt and stop consistently.

When anti-collision “overreacts” (false positives)

• Cable interference: A cable rubbing the lifting column or control box can mimic a bind. Reroute, add strain relief, and separate AC and data lines inside the tray.

• Tray contact: A deep cable tray can touch a crossbar at certain heights. Shift the tray back or lower slightly.

• Binding hardware: Loose crossbar bolts or a racked frame cause changing friction. Square the frame and torque hardware in a star pattern.

• Heavy off-center loads: Move a monitor arm clamp closer to a leg, or redistribute weight. Extremely off-center loads can look like an obstruction.

When anti-collision “underreacts” (missed stops)

• Sensitivity too low: Increase sensitivity one step and retest with foam and felt-protected obstacles.

• Compressible obstacles: Very soft objects may absorb force without a current spike. IMU-equipped systems do better here; otherwise, raise sensitivity and lower lift speed if your controller supports it.

• Firmware and ports: Update firmware if supported. Reseat motor connectors in the control box and verify columns are in the correct ports.

• Mechanical bind: If the desk hesitates at one height on every cycle, inspect lifting columns for damage, debris, or misalignment.

Safety practices that matter more than any setting

• Keep knee space clear: No loose boxes, trash cans, or hanging bricks from the tray.

• Train the basics: Show users the child lock, memory presets, and how to watch clearances when moving.

• Use presets: Memory presets reduce “hunting” and shorten motor run time, which lowers risk and keeps motion smooth.

• Maintain monthly: Wipe column exteriors, recheck torque on the frame, confirm cable slack, and run a quick anti-collision test.

What to specify when you buy

• Bidirectional detection with adjustable sensitivity.

• Documented stop-and-reverse behavior (for example, stop depth and automatic reverse distance).

• Stable motion under load: Rated speed at 30 to 45 mm/s with a defined test weight.

• Synchronization and error handling: Clear error codes on the desk controller and a simple reset procedure in the manual.

• Structural stability: Dual motors, three-stage lifting columns, long feet, and a rigid crossbar to minimize wobble-induced false trips.

Hand-over checklist for facilities

• Reset complete and memory presets saved for sit and stand.

• Downward foam test passed; upward padded-shelf test passed.

• Cable tray clear of crossbars; vertical cable chain forms a smooth S-curve at all heights.

• Controller child lock verified; quick-start card posted.

• Control box labeled with support contact and reset steps.

Anti-collision is a system, not a checkbox. It works best when a smart control box, synchronized linear actuators, and tight, stable lifting columns move a balanced surface with clean cable management. Calibrate under real load, test both directions with safe props, and set sensitivity for your environment. Do that, and your height adjustable desk will stop quietly when it should—and never when it shouldn’t.

• Explore sit stand desks, control boxes, desk controllers, and lifting columns engineered for safe, smooth motion at Venace: https://www.vvenace.com

• Contact us: tech@venace.com