There are the "consumer" negative ion detectors which are about 50 USD, reviews appear to indicate that they are not measuring very much at all. Then there are the professional ones which are $800 and up. As I understand it the customary standard measurement is in millions of ions per cubic centimeter; the precision needed is not great, 25% or 20M/cm3 will do, range 10 to 300 would be very helpful. Any ideas?
The standard measurement for a genuine, high-density negative ion generator is 1,000,000 negative ions (anions) per cm3 at a distance of 1 meter from the ionizer. That is the level that Dr. Michael Terman of Columbia University used in his well-known study of the treatment of depression using negative ions. I believe he has a patent on that.
On the web, you'll find several variations of a two-transistor negative ion detector schematic. It can be quite useful; the LED just starts to glow at ~9000 ions/cm3. (In fact, our IDS-2 ion detector was based on that circuit. Google is your friend.) And the model IG-133* series we manufactured --that generated that ion density-- made its LED just glow at 8' away from the ion emitter on those models. Therefore, it was quite useful in determining whether a particular ionizer was actually a high-density ionizer or not.
You can also make a simple but useful one with an NE-2 neon lamp in parallel with a .001 uF disc ceramic capacitor. Solder a 6" piece of bare wire to one end, and hold the other end between your thumb and forefinger. Unless a static charge has built up on your body, it will slowly blink within 6" from a high-density ionizer. We used to give these (IDN-1) away with every ionizer purchase.
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