Difference between revisions of "Magnet detector configuration v4"

Latest revision as of 15:11, 10 April 2018

General functionality description

Device works as magnet detector. Device has a connectors for magnet sensors cable. Device has groups of parameters "Magnet" and "Magnet Adv." for tuning magnet detector. And it also has two groups of parameters "Mag S1" and "Mag S2" for sensors tuning. These parameter groups allow you to configure the detection of magnets.

The system responde to a changes in the magnetic field in the range of the magnet sensors. If magnet response level is big enough corresponding to magnet detection settings this consider as alarm. So internal state is changing to alarm state, alarm counter is incrementing, common system buzzer is switching-on ("fast beeps" by default), external LED3 indication is switching-on. After a short time when magnetic field is not changing, while there is no moving magnet near sensors or it is out of the detection area, if reaction is less then magnet detection settings it consider as end of alarm. So internal state is changing to normal state, common system buzzer and corresponded external LED indication are switching-off.

For magnet detection there is a set of algorithms for elimination or decreasing a number of false alarms caused by non hard-tag detachers or non "target magnets". For this magnet detectors can use two-sensor measurements for filtering false alarms caused by "far located strong magnet" (urban transport, elevators), impulse disturbances (electrical drive of sliding doors, power converters). While iron structure has the properties of a magnet, when moving this can cause false alarm. Accordingly magnet detectors can use corresponded metal detector data for correction the magnet detection. These functions are intended for installations in outlets (or elsewhere) where iron trolleys are used.

The device can send information about the number of magnet detection alarms for a period (enabled, every 5 min by default) or immediately alarm states. Also it can send separately sensors own alarms counters and states. To do this, you need to set these variables as streams with the necessary parameters and save the changes.

Parameters description

See figure 1 for details about detection principle.

Fig. 1: An example of the alarm state changes, depending on the response value (dV) and the influence of the tuning parameters (th, in delay, out delay)

Parameters features explanation

Parameters groups Mag Sx for magnet sensor tuning.

• dV - the response of the separate sensor detector over the magnetic field. Features: [var], [float], [RW], [Monitor only].

• th - detection threshold level. The parameter value ​​is selected based on the noise level. In generally the recommendation is to select "th" at least 10 times greater that max noise dV level (without magnets). Features: [1.0], [0.25 .. 10.0], [RWS].

• Babs - [mGs] current level of magnetic field strength measured by the sensor. Features: [var], [float], [RW], [Monitor only].

• bsize - [x10 ms] the size of the history buffer for analysis.Features: [100], [1 .. 200], [RWS].

• bwindow - [x10 ms] analysis window. The bsize / bwindow ratio affects the speed and sensitivity of the magnet detection.

Features: [75], [1 .. 200], [RWS].

• in delay & out delay - [x10 ms] time delays for start detection when dV is exceeded above th and at end of detection when dV is less than th. Features: [4 & 20], [uint], [RWS].

• state - the state of magnet detection by separate sensor. Features: [var], [0, 1], [RW], [Monitor, Stream].

• alarm counter - the lifetime magnet sensor alarms counter. Features: [var], [uint], [RW], [Monitor, Stream].

Parameters groups Magnet for magnet detector tuning.

• dV - the overall response of the system to the magnetic field depended on algo. Features: [var], [float], [RW], [Monitor only].

• th - sensitivity detection setting. The parameter values ​​are selected based on the noise level. In generally the recommendation is to select "th" at least 10 times greater that max noise dV level.

Features: [2.0], [0.25 .. 10.0], [RWS].

• in delay & out delay - [x10 ms] time delays for detection when dV is exceeded & less then th . Features: [20 & 15], [uint], [RWS].

• alarm state - the state of magnet detection. Features: [var], [0, 1], [RW], [Monitor, Stream, Alarm].
• alarm counter - the lifetime magnetdetector alarms counter. Its value stored in battery backup domain. Features: [var], [uint], [RW], [Monitor, Stream].

• algo - the detection algorithm. Features: [11], [0 .. 100], [RWS].
  • 0 - Simple magnet detector. Detection is depended only on sensors sensitivity settings (Mag S 1, 2). When one of two sensors detects magnet it's consider as magnet detector alarm. dV is not calculated in this mode
  • 1, 2 - Dual magnet detector in gain sense mode 1 and 2. The main detection variable dV is calculated as a sum of each sensors responses without/with sign of values considering.
  • 10, 11 - Dual magnet detector in magnet filter mode 1 and 2. The main detection variable dV is calculated as a delta sensors responses without/with sensors space orientation considering.
  • 20, 21 - Dual magnet detector in metal filter mode 1 and 2. The main detection variable dV is calculated as a sensors responses with with metal detector data compensations. In this mode is need to tune parameters from group Magnet x adv

Parameters groups Magnet Adv. for tuning magnet detector in metal filter modes .

• trolley tau - [s] the parameter of calculating the rate of change of the metal response. Features: [0.1], [0.01 .. 1.0], [RWS].
• trolley win magnet - [x10 ms] the size of the history buffer for the analysis of changes in the magnetic field. Features: [5], [1 .. 200], [RWS].
• trolley win metal - [x10 ms] the size of the history buffer for analysis of changes during the movement of metal. Features: [10], [1 .. 200], [RWS].
• trolley AB magnet th & trolley AB metal th - ranges of dV for magnet alarm blocking by metal. Features: [12 & 100], [float], [RWS].
• trolley K2magnet - the parameter of taking into account the rate of change of the magnetic field. Features: [10], [float], [RWS].
• trolley Kmetal & trolley K2metal - the parameters of accounting for changes and the rate of change during the movement of the metal. Features: [50000 & 150], [float], [RWS].

Setup procedure

1. To assess the level of the magnet's influence, use the variable dV, which should be chosen for monitoring. The system should tuned to the best sensitivity when detecting moving magnets using the parameters th, bsize, bwindow, in delay / out delay, taking into account the noise level.

The magnet detector is evaluated using the state and counter variables, as well as based on the external LED indication.

The range of detection depends on the level of magnetic induction of the magnet, the direction of its magnetic field and the speed of motion. For tuning, you can use a standard magnetic hard-tag detacher with an induction of 6-10,000 Gauss.

2. False triggering in some cases can be caused by impulse and constant interference at the installation site, for example, when the sliding doors (especially with the DC collector drive) are close (<2 m), when power consumers switch on/off the power line (depends on Parameters of the mains), with close proximity (<0.5 m) of mains power lines, with close location (<25 m) of transport routes (metro, tram, parking). The detuning from false alarms can be performed by a load of sensitivity (increase in th), as well as an increase in the delay in triggering in delay.

3. For false alarm filtering select corresponded algo value from Magnet x group , use the variable dV, which should be chosen for monitoring. The system should tuned to the best sensitivity when detecting moving magnets using the parameters th, in delay / out delay, taking into account the noise level.