Principle Of Operation; What Comes With The Am-Fog Probe; Operating The Am-Fog Probe; Downloading The Am-Fog Connect App - Water Analytics AquaMetrix AM-FOG Installation And Operation Manual

3 Principle of Operation

As stated in the introduction, the AM-FOG analyzer works by measuring the capacitance of the
surrounding medium. The capacitance is related to an electrical property called the dielectric constant.
Materials that hold a large charge, such as air, have a high dielectric constant. Those that can't, such as
water, have a low dielectric constant. In general, insulators have high dielectric constants whereas
conductors have very low constants. Grease, or FOG, has a relatively high dielectric constant though not
as high as air.
The AM-FOG analyzer uses electrodes whose electric fields extend several centimeters into the medium.
Therefore, a coating of grease on the surface of the probe has a minimal effect on the measurement of
the capacitance. The probe consists of a number (1 to 8) 8" sensor boards attached in series, with each
board containing 8 capacitance sensing elements located at 1" intervals. Therefore, the probe length can
be anywhere from 8" to 64", with 1" resolution, regardless of size. The probe can be used in nearly all
hydromechanical interceptors and all but the largest gravity interceptors.
Firmware inside the probe communicates via Low Energy Bluetooth (BLE) to an app smart device such as
a cell phone or tablet. There is an app for both Android and iOS (iPhone) devices. Configuration,
calibration, and measurement are all done on the app.
The value of the capacitance that the probe reads is in units of frequency (Hz). Values range from about
60,000 in water to about 80,000 Hz in air. To make the user interface easier to understand the value of
the sensors in water are set to zero and the value of the sensors in air are set to 10,000. Typical FOG
values then fall into the range of 6000 to 8000.
Since each sensing element is slightly different from all others the probe must be corrected such that all
sensors give approximately the same value of 0 to 10,000 when immersed in the same medium. During
the process of calibration, the probe is immersed in water and the app assigns zero to all sensor
elements. The user then hangs the probe in air and the calibration routine assigns 10,000 to all sensor
elements. Of course these values drift by as much as 10% over several days of use so calibration must be
done on a periodic basis—approximately weekly.

4 What Comes with the AM-FOG Probe

The AM-FOG probe is a self-contained unit and has no accessories that are necessary for operation. The
only other component needed is the free app loaded onto your smart phone. The handle of the probe
will enable you to immerse the probe in the interceptor. If you need to access an interceptor that is more
than about two feet underground, you will need an extension pole with a grabber. Here is an example:
Unger 42.5 in. Steel-Rubber Rugged Trash Reacher Grabber-971340 - The Home Depot.
The probe comes with a 3" diameter PVC carrying case. The carrying case doubles as a container for
calibrating the probe in water. Simply stand the case up and fill it with water such that the level reaches
the top when the probe is fully inserted.

5 Operating the AM-FOG Probe

Downloading the AM-FOG Connect App

The interface to the probe is through an app on an Android or iOS (Apple) phone. The app is free. We are
constantly adding useful features so keep checking the app store for the latest version. (Will the app
notify the user that a new version is available and automatically install it?)
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AM-FOG Operating Manual rev 0.9