CS110 Electric Field Meter Sensor

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1. Can a CS110 be used to measure current flow and direction on electric transmission lines?

   When programmed as a “Slow Antenna” sampling at 100 Hz, the CS110 would provide polarity information but not actual current flow in the wire; therefore, Campbell Scientific does not recommend using a CS110 for this purpose.

2. If a CS110 electric field sensor is installed in complex terrain, such as on a ridgeline in alpine territory, what is the effective range (spatial range) of the instrument, and how might it differ from a flatland site?

   The following information can help determine the effective range (spatial range) of the CS110:

   • Thousands of miles: When there are no clouds in the sky, the CS110 responds to what is called the fair weather electric field created by the “global electric circuit.” Thunderstorms worldwide transfer charge to the upper atmosphere, which comes down worldwide as an electric field that varies from roughly -100 to -200 v/m on flatland sites. Our customers have indicated that the fair weather electric field is enhanced by high terrain. Interestingly, there are daily and seasonal changes to this global electric circuit.
   • 20 miles: Lightning strikes in thunderstorms as far as 20 miles away are discernable in the fair weather electric field from a flatland site. The strikes show up as sharp changes in the electric field followed by a more gradual recovery. It is unknown if the distance is greater on a high ridgeline.
   • 5 to 7 miles: When charged clouds are within five to seven miles, they can positively or negatively change the electric field above or below the fair weather electric field. Even when the actively producing cloud-to-ground lightning portion of the storm is 20 miles away, an anvil cloud from that storm that comes within five to seven miles of the CS110 will change the electric field measured by the CS110. Think of clouds attached to an active thunderstorm as electrical conductors. Even anvil clouds that were once part of a thunderstorm that has since dissipated will hold their charge for a significant period.
   • A mountain between a charged cloud and the CS110 will block the electric field influence that the cloud would have had on the CS110.

   For more information on this topic, refer to the “Cumulonimbus” section (section 3.2) of the book Lightning: Physics and Effects by Vladimir A. Rakov and Martin A. Uman.

    

3. Do the inputs on the CS110 panel board have the same (or better) surge protection as the CR1000 wiring panel?

   The CS110 uses the same gas discharge tubes, etc., so it provides similar surge protection as the CR1000. The ground paths are different, although both are intended to provide a good ground path through the ground lug on the wiring panel and the case ground hardware on the CS110.

4. Are there any problems with locating a CS110 Electric Field Meter Sensor and an SG000 Strike Guard Lightning Sensor near a tower that has spread-spectrum radios on it?

   The CS110 and the tower should be positioned away from each other a distance of three times the tower’s height.

   If the radio signal is strong enough, the SG000 may pick it up as one of the two components the SG000 measures to detect lightning. If this signal coincides with a light flash from a windshield or headlight, it could generate a false strike signal. Also, constant bombardment of the SG000 by sufficiently strong RF signals will pull the sensor out of its quiescent state, affecting its current drain. This will eventually degrade the battery and shorten its expected four-year lifespan.

5. How can an end user simulate a lightning strike to an SG000 or CS110?

   To simulate a lightning strike to the SG000, use a camera flash to flash the glass bulb from a distance of 5.08 to 7.62 cm (2 to 3 in.). Note: A flash from a cell phone usually isn't large enough to simulate a lightning strike. 

   To simulate high electric fields on the CS110, run a comb through your hair and hold it a distance of 2.54 to 5.98 cm (1 to 2 in.) from the shutter of the CS110. Other items such as plastic bags or balloons, or fur on glass, can be used as well.

6. What is the FC100 commonly used with?

   The FC100 is required to communicate with the SG000 Strike Guard Lightning Sensor. The SG000 is an option for the CS110 Electric Field Sensor and the LW110 Lightning Warning System.
7. Is there a meter that can measure the atmospheric vertical electric field without connecting to the Earth?

   The CS110 Electric Field Sensor, and field mills in general, are referred to as induction probes because the applied electric field induces charge onto sense electrodes. The amount of charge induced by a given field depends on the voltage at which the sense electrode is at.

   Normally, it is most convenient to ground the instrument, making the sense electrode at earth ground potential when measuring the vertical component of atmospheric electric field at the surface of the earth. This is because the instrument then appears to be an extension of the earth ground. For example, in a flush-mounted upward-facing configuration with the instrument earth grounded, the imaginary electric field lines will terminate on the instrument as if it were an extension of the earth ground. Negligible field distortion occurs at the instrument aperture, as if the instrument were not present. This configuration mimics the parallel plate factory calibration done on the instrument and is why a flush-mounted upward-facing configuration is used for site correction of inverted and elevated configurations.

   The instrument can be connected to other voltage potentials besides ground, or left electrically floating, although the measured results will differ because of the change in voltage between the instrument and the source of charge generating the electric field of interest. The closer the instrument voltage potential is to the voltage of a source of charge generating an electric field to be measured, the less there is an induced charge on the sense electrode. For example, if an induction probe was placed next to, and facing, a large conductive sheet that was at some voltage with respect to earth ground, and a voltage of the instrument was varied by means of a connection to the CS110 ground lug, it would be possible to adjust the instrument voltage until zero charge was induced on the sense electrode from the nearby sheet. For this to occur, the voltage applied to the induction probe would need to equal the voltage applied to the large conductive sheet mentioned. This approach can be used to determine the voltage of the sheet and is referred to as a non-contacting voltmeter. The CS110, or any induction probe for that matter, can operate as a non-contacting voltmeter with the addition of the adjustable supply.