Probe zero, Understanding the zero function – NARDA 8718B User Manual

Page 82

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Chapter 14 Probe Zero

14

Probe Zero

Understanding the Zero Function

The purpose of “zeroing” the probe and meter is to set the meter

to indicate a zero field strength when there is no measurable

field strength. The Narda 8700 series survey system maintains

measurement accuracy under all conditions by insuring that all

probes always provide true RMS (Root Mean Squared)

indications of field strength. Diode detectors, which are used in

many of Narda’s electric field probes, are always operated in the

square law region. Since the diodes are not operated in a

saturated mode to insure accuracy in multi-signal conditions,

the survey system must be “zeroed”.
The Model 8718B establishes the zero reference as a small

positive voltage inside the meter. This zero offset allows the use

of only positive voltages while handling both positive and

negative zero drift. While it is difficult to distinguish between a

positive zero drift and the presence of an actual field, a negative

indication on the meter must be due to zero drift. This is

indicated on the display by a flashing negative sign between the

field strength value and the unit of measure on the second line of

the display.

1 2 .

%

S

D

T

2 7 . 5 M A X

C F 1 .

0

A

L T

M A X R

M E N U

F R E Q

1

F1

F2

F3

F4

0

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