Leo Smith Leo at
Mon Nov 29 15:55:48 EST 1999

Jim Coe wrote:

> All these "Lie Detector" type circuits put the test subject (usually having
> a high resistance (more correctly a high "AC Impedance"), in series with a
> battery - then they amplify and detect fluctuations in the voltage or
> current in this battery circuit. Now, a battery contact - especially to a
> high impedance load, is a very squirrelly thing. Many things in that
> interface act like little batteries in series with the main battery. There
> are electrochemical effects at the connection, such as changing leaf
> moisture, mechanical (movement) effects that change the impedance with the
> slightest motion of the leaf, EM (electromagnetic, i.e. motors, light
> dimmers,radio, TV, 60Hz power wiring, etc.) interference effects from house
> wiring and radio/TV (since the interface can also have diode
> characteristics), etc. etc.

I confirm everything that Jim says. Picking up low level signals is fraught with
problems. Generally you pack so much signal processing after the detector that
unless you know what you are looking foir in advance all you are likely to get
is random and not-so-random noise generated by almost ANYTHING in the

Any thunderstorms within 5-10 miles will push pulses into unscreened circuits.

So you need to do a fairly careful design, and put the plant in a faraday cage
as well, and stick it on a huge chunk of iron, to get rid of say 95% of the
crap. Then be very careful about how you apply the electrodes. Just sticking a
piar of not quite the same metals into any organic matter wil give you some
electrovhemical effects.

Probably not worth the effort...

> In other words, this circuit is practically guaranteed to pick up and to
> generate all kinds of signals that have nothing to do with the plant -
> except for the impedance and physical characteristics of its leaf. This is
> especially true as you turn up the gain of the amplifier. In electronics,
> this is known as an "active circuit" - that is, it creates signals and
> applies them to the plant.
> So, I figured the smart thing to do would be to just use an amplifier hooked
> up to the leaf - a passive circuit which would simply amplify and measure
> as the other circuit does.
> I built a (rather good) very high impedance input balanced differential
> amplifier (to cancel out EM and very low frequency contact movement
> artifacts). I know this circuit worked well, because I could hook the
> contacts to my head and measure clean brainwave pulses on my oscilloscope.
> Brain waves on the scalp are a high impedance source (though the scalp is
> not as high as a dry leaf) and are in the tens of microvolts (millionth of a
> Volt) range - consistent with other low level biological signals.

That is pretty big signals then. I reckon that input noise is around the 1-3uV
range for that kind of amp, over the full audio bandwidth. You can get an order
better than that if you filter out the high frequencies.

> When I hooked this rig up to various plants, I got nada, nothing no signals
> at all.

Surprise :-)

> I conclude that the signals reported by "Plant Consciousness Sensors" are
> artifacts of the circuit itself and are not coming from the "consciousness"
> of the plant.
> Incidentally, I tried other sources, like eggs (talk about high impedance -
> eggshell must be practically a perfect insulator!), trees outdoors, yogurt,
> milk.

So many of these crossover scientific experiments prove to have been done
without the aid of a single competent electronic engineer :-)

>Well, I also built a couple of good "Acupuncture Point Finders", which

> clearly indicated points of very different impedance near where "Acupuncture
> Points" are supposed to be on many people. A couple of Chinese Acupuncture
> doctors thought they were pretty cool and used them.

That sorta doesn't surprise me.

> I also took Polaroid photos of two nearly identical slices of a pear - one
> on top of a "Pyramid Energy Plate" device I bought in a metaphysical
> bookstore and one on top of only the shelf. These were in mason open jars,
> to stop air currents, and were placed on a shelf in a closed nursery
> hothouse about 3 feet apart. In other words, one jar with the peach slice
> inside was on the "Energy Plate" and the other jar, with the other peach
> slice inside, was just on the shelf.
> They looked the same for many days. Then the one on the "Energy Plate"
> stopped deteriorating, while the other was eventually black and shrunken.
> When I put them next to each other on a piece of cardboard and removed the
> "Energy Plate", they were both black and shrunken in a couple of days.

That does surprise me slightly.

> Someday, I'd like to do this over, in a double-blind way, and with a dummy
> "Pyramid Energy Plate" under the "control" sample.

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