Fixed alarm – NARDA 8718B User Manual

Page 69

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68

Operating the Meter

4. The left side of the display gives the status of the fixed

alarm. It indicates whether the fixed alarm is either on

or off and the current alarm threshold setting in terms

of percent of full scale of the probe in use (1% to 99%).

5. The right side of the display indicates whether the

variable tone alarm is either on or off.

6. The bottom line of the display indicates which function

key (F1-F4) is used to turn the two alarms on or off.

Fixed Alarm

1. Use F1 (ON) or F2 (OFF) to change the status of the

fixed alarm.

2. Use the numeric key pad to enter a two-digit alarm

threshold number. This number is equal to the percent

of full scale of the measurement range of the probe in

use. For example, to set the meter to sound its alarm

at 5 mW/cm

2

when using a Model 8721D probe, which

has a full scale measurement range of 20 mW/cm

2

, set

the alarm threshold to 25%.

3. If you want to turn the variable tone alarm on or off do

that next. See Variable Tone Alarm on the following

page.

4. When you are satisfied with all the alarm settings, press

ENTER and the meter will return to the measurement

screen.

N

ote

If you change to an-

other probe with a

different full scale

measurement range,

the alarm threshold

will also change. A

setting that is often

used with shaped fre-

quency response

probes is 50% of

Standard. To set

the alarm for one of

the 8722 series

probes, which have

full scale measure-

ment ranges of 300%

of standard, calculate

the threshold setting

by dividing the de-

sired alarm level by

the full scale value.

In this case

50/300 = 16.66%.

Set the alarm thresh-

old to 17% and the

alarm threshold will

be 51% of Standard

when using a

8722 series probe.

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