Magnasensors

VD961 exit sensors

Like most loop detectors, Magnasensors reset to the ambient ferrous footprint on power up. VD961a has three sensitivity levels selected by any two output wires. Magna exit sensors are marked with a blue stripe. 

The exit sensor range is within a 1m of the sensor, but like all magnetic sensors, it depends on the ferrous content of the vehicle.

Current suffix 'A' models have a five core cable. The power wires (red & black) are isolated from the output wires (green, yellow, brown). 

The cable is 10m, but can be extended to 100m. It is recommended to place the sensor in the centre of the road at least 7m back from gate or barrier. 

VD963 presence sensors

VD963 presence sensors also reset on power up. They are identified by a red stripe. There are 3 sensitivities. The yellow cable is 10m, but can be extended to 100m.

Like all magnetic sensors, detection range depends on the ferrous content of the vehicle. The VD963a has a reliable range of 500mm from the vehicle's silhouette. 

Current suffix 'A' models have a five core cable. The power wires (red & black) are isolated from the output wires (green, yellow, brown). Sensitivity is selected by wiring, but is not the same wiring as VD961a.

It is recommended to place the sensor in the centre of the road. The presence sensor range is within 2m, so metal gates (steel in particular) need to be 2m away at all times if they are not to interfere with vehicle detection.  A wooden gate will not affect the sensor, but any automation fitted to a wooden gate should be at least 1m from the sensor. 

Presence not safety

In the context of automation, we use the word 'safety' to describe measures that protect persons or animals. A magnetic vehicle sensor will detect ferrous material, and to lesser extent, other conductive metals.

We use the word 'presence'  for a function that detects an object and maintains its output for the duration of the presence of that object (within the specified ambient creep time). In most cases, presence outputs use N/C contacts that open on detection because they are wired into a control panel's 'safety' input. 

Automation devices may be described as 'primary' or 'supplementary' safety devices. The safety of a machine may not rely on a supplementary safety device.

Presence sensors on a barrier

Presence devices, including conventional loops, have advantages on rising arm barriers. They can be placed below most aluminium barrier which have less visibility to magnetic sensors. 

Photobeams howver are the natural safety devices for parking barriers because they protect people. Specifiers are sometimes more concerned with vandalism to photobeams than public safety.