Sensors for unwinding aplication in harsh environment

MrQ · Nov 21, 2005

Hello,

I am looking for sensors to measure the roll diameter of a roll with unwinding steelwire. The max diameter is aproximately 1500mm and the min 500 mm. The sensor will be mounted aprox 200-500 mm away from the roll. I have never used sensors to measure distance before but I have read some threads and understand that the main choices are laser or ultrasonic. The resolution/accuracy is not critical 5-10mm is OK.

However my application is a little special . The roll is mounted on a vehicle that moves at aprox 10-15 km/h while unwinding. There is no roof or cover. The vehicle is used all year in Sweden. So it might be anywhere from -20'C to +50'C it may be dark or intense sun light and calm or windy.

Which type of sensor would be best in my application?

The way I understand ultrasonic sensors have problems with temperature and wind.

Laser sensors have problems with ambient light.

Is there any sensor type???

There are a lot of brands on the market. Has anyone used anything for an aplication like mine?

Steve Bailey · Nov 21, 2005

Since precision is not an issue, do you know the speed of the wire through the machine? If so, mount a rugged limit switch so that it gets tripped once per revolution of the unwind. Measure the time between each actuation of the limit switch.

Then (Wire Speed * Time between actuations)/ PI = Diameter

SimonGoldsworthy · Nov 21, 2005

What controls the unwind tension - a brake or a drive ?

MrQ · Nov 21, 2005

Steve,

Thank you for a quick reply. I have considered this but the wire speed equals the speed of the vehicle and I am not sure how accurate readings I can get from the system that controlls the speed of the vehicle.

Simon,

to make a long story short without going into details it is a brake where I control the force.

parky · Nov 27, 2005

I have used a number of ultra sonic & laser types in harsh enviroments, the ultrasonic would be best, I used one in a factory that made concrete products so very dusty & it worked a treat.

Another solution is an LDV, this is a linear potentiometer in rod form, (they look a bit like a shock absorber)these give out a 4-20ma or 0-10v proportional to the resistance, you can get these in various lengths or even produce some form of swing arm to amplify or reduce the movement, these work well but like any moving part they will have a life span shorter than electronic means.

rsdoran · Nov 27, 2005

Let me see if I have the details correct. You want to mount a sensor 500mm from the roll and detect when it goes from 1500mm to 500mm...is this correct?

I have used SICK distance measuring sensors for these type applications, some can measure a wide range of distances with teach in (set the range) and analog output.
http://www.sickusa.com/live/master/default.asp

leitmotif · Nov 27, 2005

MrQ said:
Hello,

I am looking for sensors to measure the roll diameter of a roll with unwinding steelwire. The max diameter is aproximately 1500mm and the min 500 mm. The sensor will be mounted aprox 200-500 mm away from the roll. I have never used sensors to measure distance before but I have read some threads and understand that the main choices are laser or ultrasonic. The resolution/accuracy is not critical 5-10mm is OK.

However my application is a little special . The roll is mounted on a vehicle that moves at aprox 10-15 km/h while unwinding. There is no roof or cover. The vehicle is used all year in Sweden. So it might be anywhere from -20'C to +50'C it may be dark or intense sun light and calm or windy.

Which type of sensor would be best in my application?

The way I understand ultrasonic sensors have problems with temperature and wind.

Laser sensors have problems with ambient light.

Is there any sensor type???

There are a lot of brands on the market. Has anyone used anything for an aplication like mine?

Lemme see if I understand what you are doing.
1. Mount roll of steel wire on truck.
2. Anchor end of wire.
3. Get in truck and drive
4. Wire comes off roll.
5. You do this at 15 km /hr?

What are you measuring
the length of the wire you paid out?
The length remaining on roll?
How far you drove?

Once you get this number what do you do with it?

Dan Bentler

nif · Nov 28, 2005

I think it would be better to use two pulse encoders.

One on the reel axes and one extra wheel on the wire. If you calculate the difference in the pulses you will get the diameter.
If you use pulse encoders they can be covered and won´t be affected by the weather. We have use ultrasonic devices in Finland but when the snow blows in the gauge the thing stops working.

Sensors for unwinding aplication in harsh environment

MrQ

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Steve Bailey

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SimonGoldsworthy

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MrQ

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parky

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rsdoran

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leitmotif

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nif

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