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Hi everybody,

I have a following question, I hope somebody will be able to help. Our client uses ultrasonic level sensors inside the water wells and they are having problems with spider webs. Has anybody run into problems similar to this and could suggest a solution? So far the solution has been a broom and it works perfectly except that somebody has to drive there, pick up the broom, open the hatch and do the cleaning. I will appreciate any suggestion, please brainstorm with me,

Thanks,
wesley

Yes, this is certainly possible. The spiderwebs are creating a return signal that the transmitter interprets incorrectly as a water level.

Some transmitters have adjustable blanking distances, and if the spider webs are consistently at a particular level or region, the blanking distance could be increased to ignore them.

Other physical suggestions include a nozzle with a high pressure water supply on a timer, as well as to continue to use the broom.

Walt Boyes

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Walt Boyes (wboyes@putman.net)
Editor in chief, CONTROL magazine
www.controlglobal.com
DigitalFieldInsider,SecureSystems Insider

Blogging "Sound Off" at controlglobal.com

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630-467-1301 x 368
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I have forward this on from a colleague...

I have actually,

On a storm water drain weir at Kimberly Clarke.

We used to drive there, pick up the broom, open the hatch and do the cleaning.

They could:
1) Swap to Radar - will see through the webs but they might need to clean them every year or so predictively.
2) Put a spider killer thingo [like you do in your shed] down the well, or get in the pest control guy with a long lasting type killer.
3) Seal the well to prevent spider ingress, but if the temperature is likely to cause condensation then an air purge will be required - it would need a vent so as to avoid pressurising the well. If natural air circulation currently prevents condensation then can the well be sealed with a fine gauze.
4) Mount a permanent light in the well. Spiders hate that.
5) Implement pro-active cleaning of the well
6) Encourage a wasp to take up residence in the well or
7) Swap to a non webbing model of spider.

Since you have water under pressure handy, I think a spraydown of the area on a timer would discourage the webslingers and wouldn't be vary hard to arrange. Might wash in some debris, but only the first couple times. Underground sprinkler timers from the nearest box store might be useful.

Regards

cww

I would try an insect control form and branch out from there - try http://www.bugsmart.ca

Thanks Bob Hogg

bob@almegcontrols.com

Wesley

I have used a stilling well (or collimator) in other hard to measure situations (ladders, sewage foam etc) using an ultrasonic transducer.

The technique uses a pipe of suitable diameter (depending on the ultrasonic transducer -- Milltronics works with a 6 inch PVC pipe with no seams) down to the water level and a small breather hole at the top (spiders may have a hard time finding this hole).

Dennis

The frequency of operation is the real culprit to your ultrasonic-spider web problem. Typical ultrasonics operate in the 40-60KHz range and are succeptible to interference from webs or foam. Depending on the measuring range, you could drop down to a sonic in the 15-20KHz range which will not be affected by spider webs. Hawk Measurement Systems makes a unit with variable gain along with low frequency, that does really well with changing environmental conditions.

If the buggers are doing real well and loading the face with carcasses, you could use a simple panel indicator on the analog and a timer relay to 'wash' the face with a solenoid and a low pressure water supply