Geometrics G-822A, Руководство по эксплуатации

Страница: 9 / 62

Geometrics, Inc. G-822/G-823 Magnetometer Manual
3
A single coaxial cable connected to the BNC connector on the sensor driver module
carries power to and signal from the module. This BNC connection is located next to the
interconnect cable. This coaxial cable may be as long as 200ft (61m) for interconnection
with a power/signal decoupler (e.g. Geometrics P/N 27560-01)
3.0 PERFORMANCE
Geometrics G-822A magnetometer produces a Cesium Larmor frequency output at
3.498572 Hz per nT. ‘nT’ refers to the magnetic field strength as measured in nanoTesla.
1nT equals one gamma or 10
-5
gauss. So, at the earth’s surface, in a nominal 50,000nT
field, the Larmor frequency is about 175 kHz. The output of the G-822A is a continuous
sine wave at the Larmor frequency. The typical signal amplitude is from 1 to 2 volts
peak-to-peak with the sensor in its optimal orientation.
The G-822A is intended for use in airborne, marine, land and base station applications,
and operates over the earth's magnetic field range of 20,000 to 100,000nT. Absolute
accuracy depends on sensor orientation, internal light shift and the accuracy of the
external counter's time base. Error due to orientation of the G-822A does not exceed
±0.25nT or 0.5 nT peak-to-peak (p-p) throughout the active zones shown in Figure 3.
Environmental conditions for proper operation are -35 to +50°C (-31 to +122° F),
humidity to 99 percent non-condensing, over an altitude range of 0 to 30,000 feet.
Figure 3. Active zone for the cesium-vapor sensor.