Appendix b: theory of operation, Overall functional description, Probe functional description – NARDA 8718B User Manual

Page 122: Model 8718b meter functional description, Theory of operation

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121

Appendix B Theory of Operation

B

Theory of Operation

Overall Functional Description

The meter is a portable, battery-operated instrument that forms

a complete RF Radiation Survey System when used with an

interconnected Narda 8700 Series probe. Optionally, the

system may employ a fiber optic transmitter and cable between

the probe and meter. The survey system is designed to detect

electromagnetic fields and to display the field level on the

meter’s Liquid Crystal Display (LCD). The probe detects the

electromagnetic radiation and transmits a DC signal to the

meter. The meter processes the signal from the probe for

viewing on the LCD screen. The meter displays the field levels

in various units of measure dependent on the field component

detected and the characteristics of the probe used.

Probe Functional Description

The probe senses the electromagnetic fields and develops a

signal for transmission to the meter. The probe has an isotropic

sensing pattern so that the radiation may be sensed from any

direction, except through the handle. Detectors in the probe

sense the electromagnetic radiation present and apply signals

to preamplifiers U1 and/or U2 located within the probe.

Preamplifiers U1 and U2 amplify the signals from the detectors

and route them to the meter via connector P1.

Model 8718B Meter Functional Description

The meter receives the signal(s) from the probe, processes the

signal(s) and provides a visual display of the levels detected.

The signal(s) received from the probe at PROBE connector J1 is

routed to amplifier U2. Amplifier U2 amplifies the signal(s) from

the probe and generates a signal to drive the A/D converter U3.

The output of the A/D converter is routed to microprocessor U5

that drives the LCD.

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