false tripping of a metal detector

[walleye]

i work as a maintenance electrician in a sawmill.we have had some problems with a metal detector tripping when other a machine centre shuts down for breaks.when the first machine shuts down,another machine centre also does and the control power is lost shutting it down.the vibrating conveyor mounted above the search coil was installed at the proper distance and has a fibreglass trough over it.

i have read the troubleshooting manual for the metal detector and it said to
install a .47micro farad capacitor to the coil of the magnetic starter.

i will try this at shutdown, but has anyone had to deal with this before?

 

[OkiePC]

Our SafeLine metal detectors are sometimes flaky too. We use isolation transformers for their power to help. Also, I have been told that a cellphone too close will set them off even if it is turned off.

 

[mordred]

very common problem I've worked on safeline and the two different Loma models the types of problems I've encountered with nuisance tripping are as follows. Poor power supply (make sure you check for ground to neutral feedback anything more than 1 amp and it will cause problems. Dirty conveyer belting. mechanical vibration is a very strong source of problems. leaking capacitor on the capacitor bank. (in this case you usually have to send the head to th manufacturer.) Seen in one case where it was the main board on the Loma IQ2 model. in the case of the IQ2 sometimes the compensation value is too far off to correct do the autocalibration after doing the ferrite calibration. Also for the Lomas check the ADC values in the Loma menu X and R values should stay near 0
when you have no product It been too long since I worked with Safeline to provide much help there. It may help if you can provide the make and model of which detector you are using as each is manufactured differently. Harmonics can also have a crippling effect EMF is not so common but easily assumed.

 

[milldrone]

metal detector tripping when other a machine centre shuts down for breaks.when the first machine shuts down,another machine centre also does and the control power is lost shutting it down

Are you saying the control power comes from another machine center? On every metal detector I have worked with the control power is provided discreetly. As in a separate 110V breaker.

has anyone had to deal with this before?

Yes

These can tough to trouble shoot because any random touching metal can make them "trip". To demonstrate this phenomenom take a 20 foot piece of insulated # 12 thhn strip both ends make a loop arround the metal detector coil on top of the fiberglass section. Everything should be fine at this moment then touch the stripped ends to each other and your detector should trip. This is just to illustrate the tempormental personality of these things.

So look for loose conduit and double check all wiring terminations.

Is your detector a MDI?

 

[Bruce99]

Metal Decs

Very common problem.. Check the cables and connections. The coils do not like any vibration or loose metal by the coils. We now lock the cabinets because an operator turned the sensativity to max to get time to kick back and read...cables seem to be our biggest trouble.

 

[ElectricEngy]

You may want measure if a stray voltage / current is on the grounding conductor for the detector.

Please verify that for the detector and all systems in the shared circuit / distribution panel are properly grounded (no ungrounded / grounded bonding (single point at main service only)) and that proper grounding is as the manufactures recommendations. Also, check for any large inductive loads coming on-line at the time that the detector is mis-operating

From my experience with metal detectors from food processing, the microprocessor / system is sensitive to stray voltage / current on the grounding since they rely on an a the grounding plane on the control board to maintain a solid voltage level to the microprocessor.

 

[Patrick]

I have IQ2 and Safeline. The most common cause that I have seen is the use of two way radios, and the real pain is bad bearings on the conveyor system that passes through the search head. Here at this plant all bearings on the metal detector belts is grounded.

Pat

 

[scooterboiler]

i work as a maintenance electrician in a sawmill.we have had some problems with a metal detector tripping when other a

I am a service engineer for these and inspection systems. IQ's are not very stable at the best of times and the filtering system does'nt work so great. It sounds like your interference is cuasing a surge/drop in line voltage. This causes a disturbance in the magnetic field which the processor sees as metal. I reckon the quickest way is to fit a UPS or a "good" filtering system.