Pictures

The ultrasonic waves come out of that gold-colored disk.

The black structure at the top is a water-level sensor. The unit shuts off automatically if the water level gets too low.

The mister is shown sitting on the power supply that makes it run. The power supply is, relatively speaking, huge and heavy.

It puts out 24 Volts at 1.2 Amps.

Sources

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Tips

• Never put your hands or other body parts near the "business end" of the mister. It can drive water under your skin, causing damage that feels like a burn.

• Use only distilled or deionized water. Tap water will leave mineral deposits that gum up the unit.

• Never run the unit "dry". Make sure that the unit always has at least an inch of water over it. Check the directions that came with your unit to see how much water it needs.

• Ultrasonic mist units tend to "spit" droplets of water. Anything within a foot or so will become damp. There have been suggestions of using some type of container, like a funnel, over the mister to contain spatter. I would be tempted to try some form of mesh screen, that mist could pass through, but would catch larger dropplets.

• The mist produced by this unit is fairly heavy, and will not rise up.

• Don't expect much mist from one of these.

Fixes

Water Level Sensor

Step 1 - Is there really enough water? Perhaps the sensor is correct in shutting things down.

Step 2 - Find out what kind of water level sensor you have.
These drawings show three different kinds of sensors that detect the presence of water by measuring how well electricity flows through a gap.

When there is air around, the gap doesn't conduct well, and the mister shuts off. When there is water in the gap, it conducts some electricity and the mister runs.
I have also seen mechanical water level sensors with tiny plastic floats.

Step 3 - If you have a mechanical water sensor, make sure that the float is not jammed.

Step 4 - If the sensor measures electrical conductivity through a gap, perhaps your water isn't conductive enough. It is ironic that ultrasonic misters work best with distilled water, but distilled water is a poor conductor of electricity. To see if this is the case, try running the mister in tap water. If it works there, try running in distilled water, with a little tap water mixed in.

Fog Additives

Additives work with ultrasonic foggers because the mist particles have a larger droplet size, capable of carrying stuff with them. Also, the droplets are produced by mechanical means, not thermal.

I haven't tried this yet, but would be inclined to use diet tonic water. Regular tonic water contains sugar, and ultrasonic misters tend to spatter, and you don't want sugar water splattered all over the place.

Robert Benfield (28 Feb 2001) offered the following interesting note:

A few years ago, Jem Smoke Machine Co. were making an ultrasonic fogger,
which to my knowledge was never sold publicly.  It used a 10/90 Glycol
mix.

The problem they were having, was that after 4 or 5 hours of usage, the
transducer went off frequency and required recalibrating.  In my experiment
tonight, the glycol mixture created considerably more fog than water alone,
however after about 1 minute of use it stopped creating fog altogether, even
though the 'fountain' was still there.  I'm assuming it's the same problem
Jem was having, but I'm sure they used heavier duty transducers which made
it work longer.  I thought I broke it for sure!  But I took it out, cleaned
and dried it, and it works just fine in regular water again.

Light

Since an ultrasonic mister does not chill the water, as dry ice would, you can probably use a light stick in the water to produce light without worrying about electricity.