High speed and high resolution. Breakthrough ADC technology switches from 8 to 16 bits in the same oscilloscope.
Figure 3 below shows a quiet evening when the conditions were very still. There is a slow cycle of activity visible that appeared to be a large tree situated some 50 feet from the sensor antenna swaying in the breeze.
No other source of the variation was visible, and careful observation of the instrument and the tree indicated that this was indeed the case. It is possible that the tree was acting as an antenna, and the variation is due to change in field strength.
Figure 4 shows a heavy shower with some electrical activity associated with it approaching and passing in the distance. The recording starts with a shower drifting by in the distance with a second shower approaching and causing the local field level to start rising to the point where the meter was disconnected and the experiment stopped.
Figure 5 shows the effect of charged particles from a crawler tractor being blown toward the antenna whilst it was working. The tractor in question was a large Cat D8, and the driver was throttling up to turn close to the antenna causing the spikes that can be seen to occur.
he results in Figure 6 were obtained after installing an electronic weather station, allowing more detailed observations to be made.
The experiment was started at 19:40 on the 07/06/03, the following conditions were recorded:
The data logger was set to 1 s sampling, so tending to smooth excursions, but changes look fairly slow anyway.
Visual observation indicated an evening sky, going milky blue.
The experiment was monitored, activity observed to be predominantly positive, occurred at 4200 seconds (20:50 local) coinciding with the sky becoming cloudy, but remaining dry.
By 21:25, it was getting dark, the outside temperature down to 18.9°C. with the wind still from the South West, windspeed still 1.5 m/s and the sky continuing to cloud over. The barometer remained steady at 1009.9.
Extreme caution should be exercised when using an external antenna as potentially dangerous voltages can build up.
As the weather is unpredictable this experiment should ideally be left running for extended periods of time.
Ages 16 to 19+ (Science Key Stage levels 5+)
Here the change in charge in the atmosphere can be detected and logged with an ADC-16, and the effect of approaching rain shown, together with the effects of thunderstorms and the passing over of clouds. Additionally the setup can detect the charge generated in exhaust smoke/fumes. All AS/A level Physics courses have sections on electrostatics and most courses in Meteorology would also address such phenomena. It might also provide an interesting investigative task for a slightly younger age group, though their understanding of the phenomenon and the detection technique would obviously be rather limited.