Ultrasonic Proximity Sensors

Yes, The issues with your hearing aid, I speculate it’s the frequency that may create a resonance feed back or something to that affect it.

we used ultra sonic level sensors, never had a problem with it.

If it is both hearing aids and cell phones then EMI might be the prime suspect. If it is EMI then the sound part of the ultrasonic system should not be affected but the overall ultrasonic system would still be an unknown. The EMI emissions of the welder(s) and the EMI susceptibility of the ultrasonic system would be very complex to analyze and testing them together is probably your most realistic way to get your answer.

Nasty punch line: it could be both acoustic and EMI.

The ultrasound is acoustic in nature,so it must be the electronic part of the welders that is affecting the cell phones and hearing aid.

However,some cell phones can receive and transmit ultrasound,so it could be affecting both modes.

Shielding the ultrasonic transmitter can provide some protection of the RF interference,and shielding of the circuit board is critical.

A grounded metal stilling well will give good rf protection of the probe itself

Best way to determine the viability of the system is to construct a mock-up and try it in the area of installation.

A fixed target for the sensor would give a repeatable reference point.

I constructed a mock up using a 1"x6" plank for mounting the probe,and a 1"x6" target mounted at right angles to the transmitter.

Mounted it on a cart for portability,and saved a lot of pencil-work and trial and error.

There may be a "sweet spot" where everything works just fine,or you may find no interference at all.

A fallback position is to use an old fashioned bubble tube for level detection.

They require very little air flow,about one bubble-per-second.

With the proper electronics they can be very accurate and effective.

They are still used in hostile environments where electronics cannot survive;High temperature,explosive/hazardous environs,etc.

Use a Teflon bubble tube,cut the bottom of the tube at an angle,and cut two notches in the bottom edge of the measuring tube to prevent clogging by floating coagulants.

Good luck.

I think you are barking up the wrong tree. This is not an EMI problem, it is strictly an acoustic problem. An ultrasonic welder generates the weld heat by means of very high frequency mechanical vibrations, and mechanical vibrations yield sound waves. With a well tuned welder, the sound frequency is well above the limit of human hearing ( but a poorly tuned welder can emit an ear piercing scream), but the sound appears to be effecting the receiver (microphone) in my hearing aid as well as the receiver in cell phones.

My fear is that the sound waves will likewise interfere with the receiver of the ultrasonic sensor which is tuned to the same frequency range that the welders are emitting. In addition, we have three welders operating at the same time on this line. Who knows what harmonics are being generated.

I would go as far as the frequency is higher then what a human can hear... the ultrasonics I’ve been around was very annoying.

Probably true for you, but I am deaf as a haddock. That is why I have a hearing aid

I’m not that far behind...

back in the 90’s, I had design a ultrasonic cutter for cutting the cheese ... ricotta cheese that is.

and it was irritating.

im had used a Dukane Ultrasonics and a Branson Ultrasonics. Bronson was light years ahead of the competition at the time.

I just told my boss, using this type of sensor in this situation would be like trying to have a conversation while sitting in the front row at a rock-n-roll concert.

My solution is simpeler. Use a different technology. After all I am just trying to measure the height of a loop of material as it is unwound from a coil. At the moment a dancer arm with discrete high and low on - off limits is working just fine. My boss just wanted to get more sophisticated with analog PID controls. The problem I am facing is the material is extremely elastic and must be fed into the process with minimum stretching, that is with minimum tension.

Maybe a position transmitter on the dancer? Maybe something as simple as this

I don't know anything about your application. You might need something more robust.

exactly what I have been looking for. Thank you.

Would they spend the money on acoustic curtains to knock the peaks off those pesky sound waves ?

The shaft driven pot as posted above might work well enough off a dancer arm to control your drive speed for the spool but if they want to protect other electronics and your ears then curtains at right angles to the source can achieve big percentages.

Has there been any history of premature failures in electronics around these welders ?

Mil-spec shielded cables or even just CAT 7 does wonders with EMI and HEMP if that became a factor.

Would they spend the money on acoustic curtains to knock the peaks off those pesky sound waves ?
Branson Ultrasonics calls thAt Clipped waves. I believe the added expense is nominal.

AH! The light is on:More information is given!What a concept.I was thinking liquid level control.

Now I see that we have a simpler problem to solve.

I designed a position sensor for a textile Sanforizing* operation,where the loop between the rubber belt and the drying drum was critical.

Excessive loop pulled the shrink out of the cloth.

I used a full length bar across the width of the fabric between the stages of the process.

It had counter weights to balance it precisely to follow the cloth,but not to put excessive pressure on it.

I coupled the shaft of the bar to a highly accurate potentiometer, and applied 5volts to one end of the pot, ground to the other,and simply picked off a voltage(1 to 5V on the wiper,which was proportional to the rotation,and hence the drop in the loop.

I fed the output into an A/D converter(dual slope converter) and from there into a control loop for PID control,where the digital signal was converted to engineering units for a control block,with results displayed on a local monitor.No need for a long cable runs as everything was located close to the machine.Everything was shielded and grounded by very robust sheet metal enclosures.

For calibration,I used a string pulled tight for 0% droop,and let it drop all the way down for 100% droop.

Once the optimal running position was determined,this was used as a set point for the process,and appropriate tolerances were established.

PID control was used for very fine control and to prevent drift and overshoot of corrective output.

The result was sent to a variable speed drive to control the speed of the output roller.

All fabricated by me in my shop,and it worked flawlessly for many years.

I am sure there are simpler measuring devices available now with digital output directly,but at the time(1970's) it was the way to go.

Good Luck!

*Sanforizing is a trademark of the Sanford Company

If it is an arc welding , then I believe your problem is created by harmonics!

You may need to use a Very stable power supply and very selective filtering circuit..

Hi, I think the most reliable way of receiving analog input sensors is 4-20ma. 0-10v can be affected by induced currents and voltages, but 4-20ma is far more stable.

Can't help with your other problems

Simple answer is yes. They can also cause problems with pacemaker telemetry.

How wide is the material you are controlling?

There may be an even simpler non contact method of control.

The material is 1 cm wide elastic fabric, in fact it is the elastic for the head band for a N95 face mask. As I stated, we have the process running well enough to make test samples. However, I am thinking ahead for any problems we may encounter when we ramp up to full production speed.

This is one of the directions that I am considering. I am redesigning this part of the process in a way that will make this a workable solution. I will be contacting some of our regular suppliers for this type of sensor.

Thank you for this suggestion.

Used ultrasonic level transducers in bins and tanks but found they were too susceptible to high ambient noise levels when filling tanks or bins from empty and gave false readings. The ambient noises were generated by the product striking the bin walls or splashing in bins. The tanks we changed to DP cells and the bins went to either radar detectors or sonar with lower frequencies in a pulsed mode with blanking for reflected signals, obstructions or false triggering. The blanking was done at the intelligent transmitter.

Detection ranges were 1.5 to 6m for bins and tanks. We measured stockpile profiles from 3m to 30m with multi head sensors angled to remove the chute from the target area.

Electrical discharges cause huge amount of EMP and Radio frequencies.