NARDA 8718B User Manual

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USER'S GUIDE

Model 8718B

Electromagnetic Radiation Survey Meter

P/N 42983600 RevB

narda

Safety T est Solutions

an communications company

Introduction

About the Model 8718B

Your Model 8718B is a hand-held, battery-powered meter designed to simplify the measurement of electromagnetic fields. It can be used with any Narda 8700 Series probe. The 8718B is an upgraded version of the original Model 8718. Although there are many enhancements, the 8718B is most easily distinguished from its predecessor by the quick-release style probe connector.

The meter enables you to perform both simple measurements and more demanding ones that require averaging and/or data logging. It can be mounted on a tripod and used with an optional fiber optic link for enhanced accuracy in certain applications.

Note

Return the Owner Registration Card for updates and your copy of the Applications Booklet.

Getting Started with the Model 8718B

It is important to become familiar with the Model 8718B before you use it. Chapter 2 explains the basic meter hardware. Chapters 3 and 4 cover probe selection and basic operation. The menu system, which is the gateway to all the meter’s advanced features, is the subject of Chapter 5.

It is strongly recommended that, as a minimum, you read Chapters 2-4, and preferably Chapter 5, thoroughly before you attempt to use the Model 8718B. The advanced features in Chapters 6 though 17 can then be referred to as required. Chapter 18 covers the use of the User's Software.

1Chapter 1 Introduction

User’s Guide Updates

This User’s Guide was thoroughly reviewed for accuracy prior to publication. Corrections to this guide necessitated by errors or omissions or by minor revisions to the meter firmware will be covered in the README file enclosed with the User's Software. The README file is available at any time from the HELP menu within the User's Software.

Equipment Supplied

Your Model 8718B is supplied with:

Meter

•

Battery Charger/Power Supply

•

Power Cord (230 volt chargers only)

•

Storage Case

•

Probe Extension Cable Model 8744-04

•

• Electric Field Attenuator Model 8713B

•

User's Software (CD-ROM)

•

Computer Cable

•

User’s Guide

Using this Guide with a Model 8718

The Model 8718 can be upgraded to take advantage of most, but not all, of the improvements incorporated into the Model 8718B. The upgrade includes some minor hardware changes and the installation of the Version 3.0 firmware that is described in this guide. There are only a few differences in the operation of a Model 8718 upgraded with Version 3.0 firmware versus the new 8718B. Those differences are noted in this guide.

2 Operating the Meter

Understanding Your Model 8718B

General Description

It is important to be familiar with the Model 8718B before you use it. This section includes descriptive data keyed to highlighted illustrations to help you locate the various features of the meter. The descriptions not only identify the features but tell you how they are used.

Battery Charger and Power Cord

The battery charger and power cord are used to recharge the battery within the Model 8718B.

To recharge the meter, first connect the cable of the battery charger to the larger jack on the left side of the meter. Make sure the plug is fully inserted into the jack. Connect the power cord to the wall outlet.

Note

NiCad batteries should be fully dis charged (<20% indi cation) before recharging. Charge for a minimum of 8 hours. See Checking Battery Status in Chapter 12.

The battery will be fully charged in about 8 hours. The indicator light on the charger illuminates during charging. A full charge will give you about 20 hours of operation (approximately 6.5 hours if back lighting is used).

The charger can also be used to power the Model 8718B when it is to be operated for periods beyond the capacity of the battery.

3Chapter 2 Understanding Your Model 8718B

Probe Connection

To make measurements, you must use your Model 8718B with a compatible probe. Connect the cable of the probe to the probe connector located at the top of the unit.

If you use a fiber optic link, the probe connects to a fiber optic transmitter. A fiber optic cable connects the transmitter to the rectangular fiber optic jack on the left side of the meter.

Audio Alarm

Your Model 8718B is equipped with an audible alarm that emits sound through a tiny hole on the bottom of the meter. The alarm sounds whenever the field strength exceeds the measurement range of the probe (over ranges).

You can also set the meter to sound its alarm at a specific level and/or turn on a variable-tone mode.

Probe Test Sources

Your Model 8718B is equipped with two RF sources for testing your probes. The Test Source key will turn these sources on. They will stay on for approximately 20 seconds.

A microwave (waveguide) window on the right side of the probe is used for testing high frequency probes.

A contact on the right side of the meter is used for testing low frequency probes. Most probes have three test points on the head of the probe.

4 Operating the Meter

Strap and Tripod Mount

A strap is provided on the underside of the Model 8718B. It has a hook and loop closure to permit easy adjustment, around your hand.

Behind the strap is a threaded connector used to secure the meter to a tripod. Loosen the strap to access this connector.

Operation With a Computer

To update probe calibration information or retrieve stored measurements, you must connect your Model 8718B to a personal computer and use the User's Software provided by Narda.

See Chapter 18, User's Software.

Operation With a Recorder

To obtain a continuous record of measurement over an extended period of time, you can connect a data recorder to the smaller jack located on the left side of the meter.

See Chapter 17, Operation with a Data Recorder.

5Chapter 2 Understanding Your Model 8718B

Note

The keys on the 8718B must be firmly depressed to per form their function and give a tactile feedback when prop erly depressed.

Keypad

The Model 8718B has four groups of keys distinguished by their color.

Function keys (green)

Numeric keys (yellow)

Special Function keys (white)

Power keys (blue, green)

Power Keys

Two power keys are used to turn the Model 8718B On and Off.

Function Keys

Use the four function keys

(F1-F4) to select the options displayed on the bottom line of the display screen directly above the F1, F2, F3, and F4 markings. In a few cases the options will be spelled out on the display.

6 Operating the Meter

Numeric Keypad

Use the numeric keypad to enter number data into the Model 8718B. You also use the numeric keypad to select a numbered option listed on the display screen.

Special Function Keys

Six special function keys enable you to perform specific functions.

Esc Returns you to the previous menu. In a few

cases you must enter a selection rather than use the Esc key.

Auto Enables you to automatically zero the meter Zero and probe.

Help Displays a help screen that explains your options.

Test Turns on the built-in low frequency and high Source frequency probe test sources for approximately

20 seconds.

Range Locks in a specific measurement range for the

bar graph. The digital display is not affected. The meter automatically displays a digital value over

the probe’s entire measurement range. See Bar

Graph Ranges on page 23.

Enter Stores data you entered with the numeric

keypad. Confirms an option you selected from a menu screen.

7Chapter 2 Understanding Your Model 8718B

8 Operating the Meter

Probe Selection

Introduction

The 8700 series RF measurement system offers a very broad selection of probes. The factors that you should consider in selecting the probe, or probes, best suited for your task are described in this section.

Key Factors in Selecting a Probe

FREQUENCY RANGE

POWER DENSITY OR FIELD STRENGTH

ELECTRIC FIELD VERSUS MAGNETIC FIELD

The probe frequency range should include the frequencies of all the emitters to be surveyed at one time.

The measurement range of the probe should be adequate for the field levels that you anticipate, i.e., do you expect strong fields or weak fields? Probes give more accurate and more stable readings when they are not used at the extreme low end of their sensitivity range. Therefore, if you anticipate measuring very weak fields, select a probe with a lower power full-scale measurement range to get greater sensitivity. In contrast, higher power probes give additional safety margins, especially at microwave frequencies where field strength can change rapidly with a small change in distance to the source. Select a probe with a higher power full-scale measurement range if you anticipate measuring high level fields.

Most standards recommend that you measure both electric (E) and magnetic (H) fields below 300 MHz (due to the possibility that measurements may be made in the near field). Since most experts agree that the electric field poses a greater danger at lower frequencies due to induced and contact currents that can occur, the electric field is normally measured first. Higher frequency measurements are normally made of only the electric field since measurements will generally be made in the far field.

9Chapter 3 Probe Selection

FLAT RESPONSE OR SHAPED FREQUENCY RESPONSE

Flat response probes are the most common. Narda’s patented shaped frequency response probes read out in Percent of Standard and are particularly useful in complex, multi-signal environments where exposure limits are different for the various emitter frequencies and in classified environments.

SIZE AND MINIMUM MEASUREMENT DISTANCE

The majority of the 8700 series probes have four-inch (10 cm) diameter heads. The minimum measurement distance for these probes is about 4 inches (10 cm) from the outside surface of the probe. Measurements made at closer distances can result in inaccurate readings due to capacitive coupling. The Models 8721D, 8723D, and 8725D have two-inch (5 cm) diameter heads that can be used as close as 2 inches (5 cm) from the source to the outside of the probe. These probes are ideal for the measurement of waveguide leaks. Similarly, the Model 8781D has a one-inch (2.5 cm) diameter head with a flexible shaft that is designed for locating leaks in densely packaged microwave systems.

Shaped Frequency Response Probes

The goal in designing and manufacturing a traditional, “flat” frequency response probe is to make the probe equally responsive to energy at every frequency within its rated frequency range. In contrast, Narda’s patented shaped frequency response probes are designed and manufactured so that their sensitivity mirrors a particular standard as closely as possible. For example, many of the major standards in the world set limits for maximum exposure at the lowest frequencies of 100 mW/cm in the VHF region to 1 mW/cm microwave region. A shaped frequency response probe designed for such a standard is 100 times more sensitive in the VHF region than at the lowest frequencies. The result is that energy from all sources within the probe’s rated frequency range are not only summed in terms of RMS power but are also weighted in direct proportion to a particular standard's frequency dependent exposure limits.

. These same standards typically limit exposure

and to 5-10 mW/cm2in the

10 Operating the Meter

Note

It is important to un derstand that each shaped frequency re sponse probe model is designed to conform to a par ticular standard.

The readout on the 8718B is shown in terms of Percent of Standard. The full scale of Narda’s shaped probes is typically

either 300% or 600% of a standard. This permits measurements of exposure environments where the weighted field strengths

range from as high as three to six times the maximum permissible exposure (MPE) level to environments where the

levels are less than one percent of the MPE.

Connecting a Probe

Connect a cable with a quick-release, eight-pin connector to the connector at the top of your Model 8718B. This cable will be either (1) a short adapter cable for attachment to older style 8700 series probes with integral cables or (2) a 4 ft. (1.2m) long cable with a quick-release connector on both ends for use with the 8700 "D" series probes. The D series probes have a quick-release, eight-pin connector that allows the probe to attach directly to your 8718B or be used with a cable

8700D Series Probe

8718B

Direct Connection

8700D Series Probe

8718B

4' (1.2m) cable Model 8744-04 (supplied)

8700/8700B Series Probe

8718B

1' (0.3m) adapter cable P/N 2178770 (optional accessory)

A direct connection can be useful for certain low frequency measurements. See Low Frequency Measurements in the Applications Booklet.

11Chapter 3 Probe Selection

Probe Identification

Narda 8700D series probes use the following labels and indicators:

Field Type (E or H)

Full Scale Measurement Range

Model Number

Standards (Shaped Probes Only)

Frequency Range

Serial Number

Certified Calibration Date Label

•

Model Identification Label

•

Color Band to Indicate the Full Scale

•

Measurement Range (20 mW/cm probes do not have a colored band)

• Calibration Label With Frequency

Correction Factors

Correction Factor Listed for Every Calibration Frequency

Model Number and Serial Number

12 Operating the Meter

Making a Measurement

Introduction

This chapter will help you make measurements with your Model 8718B. Information is included for turning the meter on, selecting, zeroing, and testing a probe, plus an explanation of the main measurement screen of the meter. Some general information is also included about measurement surveys, precautions you should observe, and the use of probe correction factors.

Getting Started

Press the On power key. The meter model, serial, and firmware version will be displayed briefly. After a few seconds, the Opening Menu Screen will appear.

CALIBRATION DATE

• Indicates date the meter was last calibrated

Note

See Chapter 5,

Using the Menu System, for details

on features and

operation.

CAL DATE 09 / 01 / 98 CAL DUE 09 / 01 / 99 CONNECT PROBE NOW

MEASURE MENU

F1 F2 F3 F4

To Make Measurements...

1. Select the probe you want to use and connect it to the meter.

2. Proceed as directed in Entering the Probe Model.

To access the meter’s menu system to perform some other function...

1. Press F4 (MENU). The First Menu Screen will appear. See Chapter 5, Using the Menu System.

CALIBRATION DUE DATE

•

Indicates recommended date for next calibration

13Chapter 4 Making a Measurement

Note

The single most im portant thing you must do is tell the 8718B meter which probe you are using.

Entering the Probe Model

Narda's 8700 Series system is completely modular — all 8700 series meters work with all 8700 series probes. The single most important thing you must do is tell the 8718B meter which probe you are using.

The Model 8718B has the basic characteristics of every 8700 Series probe stored in its internal memory. All you have to do is select the correct model number and the meter automatically sets the correct scales.

The Model 8718B can also store the specific calibration details for up to six probes. This includes the probe serial number, calibration date, and the calibration factors marked on the handle of the probe. Probes with this additional detail stored in the meter are referred to as probes in memory.

Putting probes into memory has several advantages:

It makes it easier to select a probe

•

Data that is downloaded after using a data logging mode

•

will include a record of the probe’s calibration date and its serial number.

•

It makes using frequency correction much easier.

Probes are put into the meter’s memory using a personal computer:

•

By Narda on the day of shipment for all probes shipped at the same time as the meter.

•

By you at any time when you use the User's Software supplied by Narda and a personal computer. Refer to Chapter 18, User's Software for detailed information regarding computer operations.

14 Operating the Meter

To select from the PROBES IN MEMORY...

1. If you haven’t already, press F1 (MEASURE).

2. The model number and the serial number of the last probe used will be displayed on the second line of the display. If you want to use the same probe, press

Enter.

SELECT PROBE MODEL A8722 SND XXXXX OR SELECT FROM L I ST

87XX 87XX 87XX MORE

F1 F2 F3 F4

3. If you want to use a different probe, look for the model number in the positions above the F1, F2, or F3 legends. If more than three probes are in memory they can be found by pressing F4 (MORE).

4. Press the appropriate function key and the probe model and serial number will be displayed on the second line of the screen. If this is correct, press Enter.

5. A new screen will appear specifying probe model number, serial number, frequency range, field type, maximum measurement range, and type of response (flat or shaped). If this information is correct, press F1. If this information does not match your requirements, you need to select another probe. Press F2 and you will go back to the Select Probe screen to make another selection.

A8742D S/N 00001

300 H -3GHzzkE-FLD

600 % STD SHAPED

YES NO MENU

F1 F2 F3 F4

6. Proceed with the probe zeroing process. See Zeroing the Probe on page 17.

15Chapter 4 Making a Measurement

To use a PROBE that is NOT IN MEMORY...

1. If you haven't already, press F1 (MEASURE).

2. The model number of the last probe used will be displayed on the second line of the display. If you want to use the same model probe, press Enter.

SELECT PROBE MODEL A8722 SND XXXXX OR SELECT FROM L IST

87XX 87XX 87XX PROBE

F1 F2 F3 F4

3. If you want to use a different model probe, select PROBE by pressing F4. If more than three probes are in memory, you will have to press F4 twice (MORE, then PROBE). One of several screens that list all 8700 series probes will appear.

1 A8722D 5 A8732D 2 B8722D 6 A8742D 3 C8722D 4 D8722D 8 NEXT

F1 F2 F3 F4

Note

4. If you see the model of the probe you want to use, press the appropriate number key. The newer "D" series

You must return to the Opening Menu Screen and repeat the probe selection and zeroing process if you want to change probes. Press 7 (Probe) from the First Menu Screen and then press F4 (RESTART).

probes are listed first.

5. If you do not see the model number you want, use the 7 (BACK) or 8 (NEXT) keys to page forward and backward until you do. Press the appropriate number key to select a probe model.

6. A new screen will appear specifying probe model number, frequency range, field type, maximum measurement range, and type of response (flat or shaped). If this information is correct, press F1. If this information does not match your requirements you need to select another probe. Press F2 and you will go back to the Select Probe screen to make another selection.

16 Operating the Meter

Note

Position the probe in the case with one test point pointed downward and the other two test points above the foam. This will insure that the test points are not touching the foam.

A8722D SNXXXXX 300 H -50GHzzkE-FLD 300 % STD SHAPED

YES NO MENU

F1 F2 F3 F4

7. Proceed with the probe zeroing process.

Zeroing the Probe

The probe and meter must be “zeroed” together. It is important that the probe is not exposed to radiated fields during the zeroing process. The storage case is shielded and provides a convenient “zero density” environment.

To zero the probe...

1. Place the probe in the storage case. Be careful not to move the probe while zeroing takes place (on probes with low frequency test points, you can create static which will give inaccurate results).

2. When you are ready, press the ENTER key. The screen will say ZEROING.

3. The meter will beep and the main measurement screen will appear in about 15 seconds after zeroing is completed.

If you get a message that the probe could not be zeroed, the most likely causes are:

•

The probe is not connected properly. Check the connector and retry.

•

The meter is set for a fiber optic input and you are using the standard cable input (or vice versa). Turn the

meter off. Turn the meter back on and press

(F4) (MENU) to access the menu system. Press 8 (NEXT) to get to the Second Menu Screen. Press 3 (CABLE/FO) to the probe input status. Press F1 (OK) if it is correct or F4 to select the alternate. Then press Esc to return to the Opening Menu Screen.

17Chapter 4 Making a Measurement

Note

See Chapter 12, Probe Zero, for additional infor mation on the char acteristics of the survey system including the causes of zero drift.

The field strength is not low enough. Move away from

•

the RF field source, use the storage case to zero the probe.

The probe is damaged. Try another probe.

•

To reconfirm the zero while the instrument is in use...

1. Establish a zero density environment for the probe as before.

2. Press the Auto Zero key. This will automatically “touch up” the zero and correct for any drift in a few seconds.

Measurement Display Screens

There are two display screen options:

The Main Measurement Display Screen.

•

The Alternate Measurement Display Screen.

•

Main Measurement Display Screen

The Main Measurement Display Screen shows a maximum value on the third line of the display. The Alternate Measurement Display Screen provides frequency-specific, real time information instead of a maximum value.

18 Operating the Meter

Main Measurement Display Screen (Shaped Probes)

MAXIMUM VALUE

Indicates the

• maximum value that has occurred since you began making measurements or since resetting the maximum using

F2 (MAXR)

The unit of measure is

• the same as for the instantaneous value shown on the line above.

BAR GRAPH

Indicates approximate

• field strength

100 segment, three

• 10:1 (10 dB) ranges

12.1 % STD

27.5 MAX CF 1.00 ALT MAXR MENU FREQ

F1 F2 F3 F4

F1 Change to the

Alternate Measurement Display Screen

F2 Reset the

Maximum Value to the current Field Strength displayed on the second line

F3 Go to the First

Menu Screen

F4 Allows you to enter

or change the frequency that you are correcting for probe frequency deviation

FIELD STRENGTH

Indicates actual measured value

• Unit of measure is always % STD

• for shaped frequency response probes

PROBE FREQUENCY CORRECTION

CF = 1.00 indicates

• no correction factor is being applied

CF= X.XX indicates

• the numeric value that is being applied

A frequency displayed

• here indicates that the meter is applying a correction factor based on the stored calibration data for the specific probe in use.

FIELD STRENGTH

•

Indicates actual measured value

•

Unit of measure can be changed by going to the First Menu Screen

Main Measurement Display Screen (Flat Probes)

The Main Measurement Display Screen for flat frequency response probes is the same as the screen for shaped frequency response probes except as indicated below.

6.26 /Wmcm

11.5 MAX CF 1.00 ALT MAXR MENU FREQ

F1 F2 F3 F4

19Chapter 4 Making a Measurement

Note

The Alternate Mea surement Display Screen should only be used for single frequency measure ments or where all emitter frequencies are close and the ex posure standard has the same limits. Re fer to Using Probe Correction Factors on page 24.

Alternate Measurement Display Screen

The Alternate Measurement Display Screen is very similar to the Main Measurement Display Screen with one difference. This

display mode is used to show frequency-specific, real time information on the third line of the display instead of a maximum value. It should be used only for single frequency or narrow band measurement applications. The information that is shown depends on whether a flat frequency response probe or a shaped frequency response probe has been selected.

Flat Frequency Response Probes. This display mode

•

instantly converts the measured value to a percent of the referenced exposure standard at a particular frequency.

Shaped Frequency Response Probes. This display

•

mode instantly converts the measured value, shown in Percent of Standard, to an equivalent power density value at a particular frequency.

The use of the Alternate Measurement Display Screen also introduces an automatic correction for probe frequency deviation for probes in memory.

The option to change display screens is only available when other options such as spatial averaging, data logging or time averaging have not been turned on.

To use the Alternate Measurement Display Screen...

1. Make sure that the 8718B is set to the correct exposure standard. See Chapter 11 Using the Standards Feature.

2. Press F4 (FREQ) from the Main Measurements Display Screen. A new screen will appear to allow you to enter a frequency.

3. Enter the frequency that you are measuring. You must fill all four positions. If you make a mistake just enter more digits until correct. For greater accuracy, use the units that allow the larger number. For example, enter

10.00 kHz, not 00.01 MHz.

20 Operating the Meter

Alternate Measurement Display Screen (Shaped Probes)

BAR GRAPH

Indicates approximate

• field strength

100 segment, three 10:1

• (10 dB) ranges

FIELD STRENGTH

Indicates actual measured value

• Unit of measure is always % STD

• for shaped frequency response probes

CALCULATED FIELD STRENGTH

Displays field strength

• in mW/cm been calculated from the % STD reading using the referenced standard and the indicated frequency

that has

12. % S DT

0.61 Wmm zc/

10.00 HG

AM I N MAXR MENU FREQ

F1 F2 F3 F4

F1 Change to the

Alternate Measurement Display Screen

F3 Go to the First

Menu Screen

F4 Allows you to enter

or change the frequency that you are correcting for probe frequency deviation

PROBE FREQUENCY CORRECTION

CF = 1.00 indicates

• no correction factor is being applied

CF= X.XX indicates

• the numeric value that is being applied

A frequency displayed

• here indicates that the meter is applying a correction factor based on the stored calibration data for the specific probe in use.

Alternate Measurement Display Screen (Flat Probes)

The Alternate Measurement Display Screen for flat frequency response probes is the same as the screen for shaped frequency response probes except as indicated below.

CALCULATED PERCENT OF STANDARD

•

Displays percent of standard that has been calculated from the field strength reading using the referenced standard and the indicated frequency

.26 Wmmc/

125.2% STD 10.00 HzG AM I N MAXR MENU FREQ

F1 F2 F3 F4

FIELD STRENGTH

•

Indicates actual measured value

•

Unit of measure can be changed by going to the First Menu Screen

21Chapter 4 Making a Measurement

Note

Alternate values can not be calculated at low frequencies for standards with very high magnetic field limits. A “greater than” symbol (>) is shown under these conditions.

4. Change the units (if needed) by pressing either F1 (kHz), F2 (MHz), or F3 (GHz).

5. Press F4 (SAVE). The probe correction factor will be displayed briefly if you are using a probe in memory and you will automatically return to the measurement screen. See Using Probe Correction Factors on page 24.

6. From the Main Measurement Screen press F1(ALT)to select the Alternate Measurement Display Screen.

To return to the Main Measurements Display Screen...

1. From the Alternate Measurement Display Screen, press

F1 (MAIN) to select the Main Measurements Display Screen.

22 Operating the Meter

Note

The Range Key only affects how the bar graph displays infor mation.

Bar Graph Ranges

The Range key is used to control how the bar graph displays information. The digital display is not affected and the meter automatically displays a digital value over the probe’s entire measurement range. There are four available settings: AUTO, HIGH, MID, and LOW. The bar graph has 100 divisions.

You will probably find it convenient to use the AUTO setting most of the time, but under a few conditions you may find one of the three fixed ranges useful. The following table illustrates how the range setting will affect the bar graph. For simplicity, a probe with a full scale rating of 100 mW/cm example.

Range Measurement Range

AUTO As the field level increases the bar graph

automatically switches between three ranges:

0.01 to 1, 1 to 10, and 10 to 100.

HIGH 1to100

MID 0.1 to 10

LOW 0.01 to 1

is used as an

If you exceed the upper limit of either the MID or LOW range, the bar graph will be replaced with the message RANGE OVERLOAD. The digital display will continue to show the correct value. If you exceed the full scale measurement range of the probe, the word "OVERLOAD" will appear

Testing the Probe

Your Model 8718B is equipped with two RF sources for testing probes. Press Test Source and both sources will stay on for approximately 20 seconds.

A contact on the right side of the unit is used for testing low frequency probes and the low frequency section of ultra-broadband probes. Most probes have three test points around the head of the probe. Position the probe so that one of the test points touches the contact on the meter. You should

23Chapter 4 Making a Measurement

Note

A probe that does not show a move ment of the bar graph for all three (or six) tests may be damaged and should not be used to make measurements.

get a deflection on the bar graph but the amount of deflection is not important. Repeat for the other two test points to insure that the probe is working correctly. The D series magnetic field probes have a single, conductive test point that is used to simultaneously test all three sensors.

A microwave window on the right side of the probe is used for testing high frequency probes. Hold the probe parallel to the right side of the meter and position the probe head against the test window so that one of three arrows on the probe is pointing towards the window. These arrows indicate the location of the three sensors inside the probe. A deflection of any magnitude on the bar graph is acceptable. Repeat for the other two sensors to insure that the probe is working correctly.

Ultra-broadband probes contain both high frequency and low frequency sensors. These probes require six checks – three high frequency and three low frequency.

Using Probe Correction Factors

All probes have a certain amount of frequency sensitivity. Frequency sensitivity is the amount of deviation from the correct measured value that a probe yields at various frequencies. Obviously, the smaller the deviation, the better. But since a certain amount of frequency deviation is unavoidable, the more frequencies that you calibrate the probe at, the better. At each calibration frequency, you have a correction factor.

Multiplying the reading on the meter by a correction factor marked on the handle of a Narda 8700 Series probe compensates for the probe’s frequency sensitivity. The Model 8718B is unique because it can perform this task automatically.

Correction factors can be used:

•

When there is only a single emitter being surveyed.

•

When there are multiple emitters all operating at the same frequency (this is often the case with industrial equipment).

24 Operating the Meter

Note

Do not use correction factors in a broadband, multi-emitter environ ment.

When there are multiple emitters with frequencies that

•

are close to each other and the nearest calibration frequencies have very similar correction factors.

Correction factors should NOT be used:

When the frequencies of the emitters are diverse.

•

Correction factors may vary considerably and there is no way to determine the distribution of energy from the various emitters. It is more accurate not to use a correction factor under these conditions. See Measurement Uncertainty on page 27.

To use a correction factor for a probe in memory...

1. Press F4 (FREQ) from the measurement screen. A new screen will appear to allow you to enter a frequency.

2. Enter the frequency for which you want to correct readings. Make sure you fill in all four positions. If you make a mistake just enter more digits until correct. For greater accuracy, use the units that allow the larger numbers. For example, enter 10kHz, not 00.01 MHz.

3. Change the units (if needed) by pressing either F1 (kHz), F2 (MHz), or F3 (GHz).

4. Press F4 (SAVE). The meter will automatically calculate the correction factor for the frequency you have entered from the two closest correction factors that were stored when you put the probe in memory. The calculated numeric value will be displayed briefly before the meter automatically returns to the measurement screen. See page 64 for a more complete description.

5. The frequency that you are correcting for will be displayed on the right side of the third line of the display.

25Chapter 4 Making a Measurement

To use a correction factor for a probe NOT in memory...

1. Press F3 (MENU). The First Menu Screen will appear.

1 DATA LOG 5 UNI TS 2 TIME AVG 6 RS232 3 SPAT I AL 7 PROBE 4 BAT/LIFE 8 NEXT

F1 F2 F3 F4

2. Press 8 (NEXT) to access the Second Menu Screen.

1 COR FACT 5 ALARM 2 SETTINGS 6 STNDS 3 CABLE/FO 7 BLANK 4 LOCKOUT 8 BACK

F1 F2 F3 F4

3. Press 1 (COR FACT). A screen will appear that shows the correction factor.

4. Use the correction factors on the handle of the probe to determine the appropriate correction factor and then use the numeric keys on the meter to enter this value. Enter a three digit number, ignoring the decimal point, and rounding to two digits to the right of the decimal point. If you make a mistake, just enter more digits until correct. For example, to enter a correction factor of 1.22, simply enter 1, 2, and then 2 while a correction factor of 0.94 is entered as 0, 9, and 4.

5. Press Enter to save this correction factor. The meter automatically returns to the measurement screen.

6. The numeric correction factor will be displayed on the right side of the third line of the display in the form CF X.XX.

26 Operating the Meter

Checking or Changing the Probe Model

To check the probe model that the meter is currently set to...

1. Press F3 (MENU). The First Menu Screen will appear.

2. Press 7 (PROBE). A Screen will appear that shows the model number and basic characteristics of the probe. The probe serial number is shown for probes selected from memory.

8712D SN 12345

300MHz z50GH E_FLD

20 Wmcm/

OK RESTART

F1 F2 F3 F4

3. Press F1 (OK) key to return to the First Menu Screen.

4. Press Esc to return to the Measurement Display Screen.

To change to another probe without turning the meter off...

1. Press F3 (MENU). The First Menu Screen will appear.

FLAT

2. Press 7 (PROBE). A screen will appear that shows the

model number and basic characteristics of the probe.

3. Press F4 (RESTART) to return to the Opening Menu Screen. Press F1 (MEASURE) and begin the probe selection process.

Measurement Uncertainty

The uncertainty of any measurement includes several factors related to the probe and meter.

•

Frequency response or frequency sensitivity is typically ±1 dB to ±2 dB (from about ±25% to about ±55%). The correct use of correction factors can greatly reduce the amount of uncertainty associated with frequency response.

27Chapter 4 Making a Measurement

Ellipse ratio is ±0.75 dB or better, depending on the

•

model of the probe. The ellipse ratio is the ratio of readings that occur when one rotates the probe around the axis of its handle. Narda calibrates its probes by rotating the probe about its axis and using the mean value to determine the correction factor. If you rotate the probe around its axis and use the mean value, ellipse ratio can be eliminated as a source of uncertainty.

Isotropic response is the error that occurs when the

•

probe is pointed in different directions. It includes the ellipse ratio plus some additional uncertainties. Although the probes pick up energy from all directions, they are most accurate when pointed at the source of energy. Generally speaking, the isotropic response is no greater than the ellipse ratio providing that the probe is pointed towards the source.

Calibration uncertainty represents another 0.5 dB.

•

The Model 8718B meter has a maximum uncertainty

•

of ±3%.

A good rule of thumb is that the total uncertainty is no greater than ±3 dB when correction factors are not used, providing that the probe is pointed at the source of energy. There are other issues related to field perturbation that can be more significant sources of uncertainty. See Field Perturbation in Measurement in the Applications Booklet.

Making a Measurement

Refer to the Applications Booklet for both general and specific information on making measurements.

Precautions

When making measurements of electromagnetic fields, a potential exists to expose yourself to excessive levels. Approach the source of energy slowly and begin making measurements from a distance at which low field levels exist. Be prepared to evacuate the area immediately if RF field levels in excess of the applicable standard are observed.

28 Operating the Meter

Using the Menu System

General

The menu system allows you to store data and to select various operating modes. It is accessed by pressing the appropriate function key that corresponds to MENU on the bottom line of the display screen. The menu is comprised of two menu screens and several sub-menus. Press the number on the keypad that matches the number on the menu to make your selection.

Instructions or sub-menus appear when one of the basic menu options is selected. Press the Help key or refer to the appropriate chapter of this guide for detailed instructions.

The following keys are used to move through the various menu options and to set measurement parameters:

Function Keys

F1-F4

Numeric Keys

0-9

ENTER

Key

key

ESC

Most menu options are offered on the fourth (bottom) line of the display. Simply press the function key that matches the marking just below the display.

Used to make a selection where options are listed on several lines of the display. Often, multiple options are listed in two columns.

Used to input a specific value or range (frequency, data logging interval, time and date, etc.).

Press the ENTER key after entering a numeric value to complete the selection process.

Press the ESC key to return to the previous screen without making a selection.

29Chapter 5 Using the Menu System

First Menu Screen

1DATALOG 5UNITS 2 TIME AVG 6 RS232 3 SPATI AL 7 PROBE 4 BAT/ L I FE 8 NEXT

F1 F2 F3 F4

Key Menu Options Chapter

Log with time and date stamp.

DATA LOG

Log spatially averaged values with time and date stamp.

Continuous logging at various rates.

TIME AVG

3 SPATIAL

4 BAT/LITE

UNITS

RS232

PROBE

8 NEXT

Turn fixed time averaging (various duration) on or off.

Turn the spatial averaging mode (used for whole body averaging) on or off.

Check battery charge status and estimated time remaining.

Turn the back light on or off.

Select from all appropriate units of measure (i.e., mW/cm probe in use. Percent of Standard is the only unit of measure for shaped frequency response probes.

Change the baud rate.

Turn the RS232 port on or off. (Automatic on for Model 8718B. Menu is for Model 8718 only)

Show the model and serial number of the probe in use.

Select another probe and restart the zeroing process

Go to the Second Menu Screen.

, V/m, V2/m2) for the

30 Operating the Meter

Second Menu Screen

1COR AFCT 5ALARM 2SETTNIGS 6STNDS 3CABLE/FO 7BLANK 4LOCKOUT 8BACK

F1 F2 F3 F4

Key Menu Options Chapter

COR FACT

SETTINGS

3 CABLE/FO

LOCKOUT

ALARM

STNDS

Enter a numeric probe correction factor. 4

Check or set the meter’s internal clock (time/date)

Enter a value for temperature. Used when the probe is separated from the meter and operating at a different ambient temperature.

Clear the memory of logged data.

Set the function keys for right or left handed operation.

Adjust the display contrast.

Select between the standard probe cable input and the fiber optic receiver.

Lock the keypad so that settings will not accidentally be changed. To release, press ENTER and ESC together.

Turn the audio alarm on or off.

Set the alarm threshold in terms of percent of full scale of the probe in use (1% to 99%).

Turn the variable tone alarm on or off.

Check or set the standard that is referenced for various measurement options.

BLANK

BACK

Blank the display and lock the keypad. To release, press ENTER and ESC together.

Return to the first menu screen.

31Chapter 5 Using the Menu System

Menu Commands

The following is a list of menu commands that are shown on the fourth line of the display and selected by using the four function keys (F1-F4).

AUTO Auto – returns the meter to the normal,

automatic temperature correction mode.

ABORT Abort clearing the memory

BEGIN Begin – confirms that the meter is ready to

perform time averaging to meet the requirements of a specific standard.

CABLE Cable – changes the meter input from fiber optic

receiver to the standard cable input.

CANCEL Cancel making the selection and return to the

previous menu.

CONT Continuous – initiate logging for an undefined

interval.

CLEAR Clear the memory of logged data.

CLR Clear the screen and return to making real time

measurements.

DISCARD Discard this data point without storing it.

END End the logging run or averaging interval.

FO Fiber Optic – changes the meter input from the

standard cable input to the fiber optic receiver.

FREQ Frequency – change or enter a frequency.

GHz GHz – used to enter a frequency.

HR Hours – used to define a logging interval.

kHz kHz – used to enter a frequency.

LEFT Left – set menus for left-handed operation.

LOG Log the current measured value.

32 Operating the Meter

MAIN Main – switch to the Main Measurement Display

Screen.

MAXR Maximum Reset - reset the maximum value to

the instantaneous value.

MEASURE Measure – begin the measurement process by

selecting and zeroing the probe.

MEM Memory – display the available memory.

MENU Menu – access the First Menu Screen.

MIN Minutes – used to define a logging interval.

MHz MHz – used to enter a frequency.

NO No – the current probe selection is incorrect.

Return to the menu to make another selection.

OFF Off – turn special mode off.

OK OK – continue with the same setting.

ON On – turn special mode on.

PAUSE Pause during data logging or time averaging.

QUIT Quit special mode and return to the standard

measurement screen.

RESTART Restart the probe selection and zeroing process.

RGT Right – set menus for right-handed operation.

SAVE Save the data point or the new setting.

SEC Seconds – used to define a logging interval.

SET Set the time, date, temperature, or display

contrast.

START Start averaging or data logging.

STNDS Standards – access the menu of available

exposure standards.

STOP Stop the current averaging run.

YES Yes – the current probe selection is correct.

Proceed with zeroing process.

33Chapter 5 Using the Menu System

Default Conditions Upon Turn-On

The Model 8718B is designed to automatically return to a basic set of operating parameters every time it is turned on. Although in some cases this may require additional key strokes to set up the meter as desired, this feature is designed to minimize the chance of making measurements while unknowingly having the meter incorrectly configured.

The table below lists the operating parameters that can be expected upon turn-on.

Parameter Default Condition

Alarms Last Used settings will be used

Back Light OFF to conserve battery power.

Blank Out OFF – display will be active.

Cable/Fiber Optic Last Used input will be active.

Data Logging OFF

Display Contrast Last Used setting will be in use.

Display Screen Main Measurement Display Screen

Lockout OFF – keypad will be active.

Probe Model Last Used probe model will be featured

on the probe selection screen.

Right/Left Last Used setting for function key

location will be in use.

RS232 Port OFF to conserve battery power.

Spatial Averaging OFF

Standard Last Used standard will be referenced.

Temperature OFF – the meter will sense ambient Correction temperature and automatically correct.

34 Operating the Meter

Time Averaging OFF

Unit of Measure Last Used unit of measure will be in use

if previous and current probe both have flat or shaped frequency response. If current probe is shaped, unit will be % of STD. If current probe is flat and previous probe was shaped, then unit

will be mW/cm

35Chapter 5 Using the Menu System

36 Operating the Meter

Units of Measure

Available Units of Measure

The 8718B Meter allows you to quickly select any unit of measure that is appropriate for the probe in use. The available units of measure depend on whether the probe is designed to measure the electric field or the magnetic field. It also depends on whether the probe has a “flat” frequency response or a “shaped” frequency response. The available units of measure for the various types of probes are:

Note

Percent of Standard is the only unit of measure available for shaped fre quency response probes. Shaped probes have fre quency response curves designed to mimic a particular exposure standard. See Chapter 3, Shaped Frequency Response Probes.

Field Component

Electric Flat

Magnetic Flat

Frequency Response

Units of Measure

mW/cm

2/m2

mW/cm A/m, A

,W/m2, V/m,

,W/m2,

2/m2

, pJcm

Electric Shaped Percent of Standard

Magnetic Shaped Percent of Standard

37Chapter 6 Units of Measure

Changing the Unit of Measure

To change the unit of measure that the meter is set for ...

1. Access the menu system by pressing the function key that corresponds to the legend below MENU on the bottom line of the display.

2. Press the number 5 on the keypad to select UNITS from the First Menu Screen. A screen will appear that offers the available units of measure for the probe in use.

1mW/c2m 2W/m 3V/m 7pJ/cm

6V2/m

F1 F2 F3 F4

3. Press the number key on the keypad that matches the desired unit of measure. For example, pressing

selects mW/cm

as the unit of measure. This unit of

measure is available for all probes with a flat frequency response.

4. The meter will automatically return to the measurement screen. If you had accessed the menu system from the Opening Menu Screen, you will return to that screen.

38 Operating the Meter

Spatially Averaged Measurements

Understanding Spatial Averaging

The major standards concerned with human exposure to radio frequency radiation specify maximum exposure levels averaged over the whole body. The co-linear dipole antenna arrays that are very common in modern wireless communications systems, for example, have multiple lobes close to the antenna. The field strength typically varies by 6-7 dB along the length of an array. Therefore, the measured value is highly dependent on not only the distance from the antenna but the height above the ground.

The traditional method of making spatially-averaged measurements is to use a “storypole”. A storypole is a non-conductive pole , often wooden, equal in height to an average adult with distance marks equally spaced along its length. Measurements are made alongside the storypole at each height and then mathematically averaged. The height and spacing of each measurement varies from standard-to-standard. For example, the IEEE C95.1-1999 standard specifies measurements from 0 centimeters (ground level) to 200 centimeters in 20 centimeter increments. Some exposure standards, such as Canada’s Safety Code 6, require that measurements be averaged across two dimensions – vertically and horizontally. Modern wireless communications sites make this manual technique more difficult than ever since field levels at many sites, particularly multi-user sites, are constantly varying. For example, paging systems go on and off and the number of cellular channels in use is constantly changing. Thus, a series of measurements made at varying heights can vary more as a function of time than location.

39Chapter 7 Spatially-Averaged Measurements

Spatial Averaging with the 8718B

The Model 8718B uses time to quickly make precise, spatially averaged measurements. With the 8718B set for spatial averaging, press the F1 function key to start the timer. Pressing the same key again stops the timer. During this interval of time, the meter takes a large number of measurements. The results are presented as both an average value and a peak value. Effective measurement technique requires you to simply move the probe slowly from toe-to-head while the timer is running. Although this technique may not be specifically called out in a particular exposure standard, it is technically sound and much more accurate than averaging a series of measurements. It is anticipated that future updates of the major standards will reflect this automatic technique now that the survey equipment makes it practical.

To make spatially averaged measurements ...

1. Access the menu system by pressing the function key that corresponds to the legend below MENU on the bottom line of the display.

2. Press the number 3 on the keypad to select SPATIAL from the First Menu Screen.

SPAT IAL AVERAGING

MOD E I S ON

ON OF F

F1 F2 F3 F4

3. Press F1 (ON).

4. The meter will automatically return to the measurement screen with new options for the function keys. If you had accessed the menu system from the Opening Menu Screen (where the calibration dates are shown), you will return to that screen.

5. Holding the meter in one hand and the probe in the other, touch the head of the probe to the ground.

40 Operating the Meter

6. Press F1 (START) while slowly moving the probe vertically at a constant rate of movement.

Note

It is important to move the probe vertically at a con stant rate to obtain an accurate spa

tially averaged measurement.

Note

The averaging time resolution is approxi mately 1/4 second.

24. % S DT

39.5 MAX

TSART MAX MEN QU I T

F1 F2 F3 F4

7. Strive for an interval of about ten seconds between starting and stopping the timer. The meter will beep every second as a timing aid.

8. When the probe reaches the height equal to the top of an adult’s head ( about 6 ft./1.9 m), press F1 again (STOP).

12. % S DT

39.5 MAX S TOP

Fl F2 F3 F4

9. The meter will show the average value on the second line of the display and the maximum value on the left

side of the third line of the display. The bar graph will be indicating the instantaneous field magnitude in real time. The averaging interval will be shown on the right side of the third line, which can be useful in perfecting your spacial averaging technique.

17. % S DT

39.5 MAX

TSART

CLR

MENU QUIT

F1 F2 F3 F4

ERAGE

SEC

41Chapter 7 Spatially-Averaged Measurements

10. To make another spatially averaged measurement, press F1 (START) again.

11. To temporarily suspend the spatial average mode and make real time measurements, press F2 (CLR). To make another spatially-averaged measurement, press F1 (START) again.

12. To end spatial averaging altogether, press F4 (QUIT). The meter will automatically return to the standard measurement screen. If you had accessed the menu system from the Opening Menu Screen, you will return to that screen.

13. To initiate spatial averaging again at a later point, use the menu system to select SPATIAL from the First Menu Screen.

42 Operating the Meter

Data Logging

Logging Options

The 8718B Meter features several methods of collecting data. The basic choices are:

Logging Data with the Meter. The logged data stored

•

in the meter is downloaded to a computer at a later date using the User's Software, where it can be viewed and printed. The data can also be exported in spreadsheet or database formats for further processing.

Continuous Output to a Computer. Data collection, if

•

any, is performed by the computer.

•

Analog Output. An analog voltage is continuously available for use with a Chart Recorder or A/D converter.

Mode 1

Logging Data

The 8718B has three logging modes to collect field strength measurements, store the data in the meter’s memory, and later export the data to a personal computer via the RS232 port on the top of the meter. The three logging modes are:

•

Collect a series of up to 999 data points, one at a time, and automatically assign a reference number to each data point. The reference numbers can refer to either site plan locations or to a diagram of the industrial equipment being surveyed. Each data point also has a time and date stamp.

43Chapter 8 Data Logging

Mode 2

Collect a series of up to 999 spatially-averaged data

•

points, one at a time, and automatically assign a reference number to each data point. Both the average value and the maximum value at each location are stored. The reference numbers can refer to either site plan locations or to a diagram of the industrial equipment being surveyed. Each data point also has a time and date stamp.

Mode 3

Automatically collect a series of data points at specific

•

intervals of time for a specific time period. Each data point also has a time and date stamp.

Format for Logged Data

A record contains a header and one or more data points. Each record is identified by a user-defined two-digit survey number and the time and date the survey was performed. The header defines the serial number of the 8718B meter, its calibration date, the probe model used, and a number of other settings. These settings may include logging rate, frequency correction, averaging mode, and averaging time.

If the probe used was selected from memory, the header will also include the serial number of the probe and its calibration date.

44 Operating the Meter

Note

If you access the menu system from the Opening Menu Screen, you will re turn to that screen. Once a probe has been selected and zeroed, the measure ment screen will re flect the logging mode that you have selected.

To initiate one of the three logging modes described above...

1. Access the menu system by pressing the function key that corresponds to the legend below MENU on the bottom line of the display.

2. Press the number 1 on the keypad to select DATA LOG from the First Menu Screen.

3. A new menu will appear, presenting the three logging

modes. If any of the three logging modes is currently active, the line showing that option will be flashing.

1LOGWITHREF # 2LOGAVGWITHREF# 3 CONT I NUOUS LOGG I NG

MEM QU I T

F1 F2 F3 F4

4. To review the available memory before beginning to make logged measurements, press F2 (MEM).

5. A screen will appear showing the approximate amount of available memory and the amount of memory already used. The bar graph is a rough indicator of remaining memory capacity as a percentage of total capacity. See Memory Capacity at the end of this chapter for information on how to determine the number of additional measurements that can be stored.

AILALB

10 B AVAI

L, 15

MENU QUIT

ORY

SED

Bkk

F1 F2 F3 F4

6. Press Esc to return to the logging menu screen.

7. To turn off the logging feature, press F4 (QUIT).

45Chapter 8 Data Logging

Mode 1 Logging

To initiate Mode 1 logging (a series of data points with a reference number assigned to each data point)...

1. Press the number 1 on the keypad to select LOG WITH REF # from the logging menu screen.

2. A screen will appear requesting that you assign a twodigit survey number to this logging run of data points. Use the numeric keypad to enter the two-digit number and then press F1 (OK)orENTER. Make note of this number so that you can later associate this survey number with the data points collected. If you make a mistake, press F2 (CLR) to clear the screen and enter a new survey number.

NEW L OGG I NG RUN :

ENTE

OK CLR MENU QU I T

NEW FRNO.__

F1 F2 F3 F4

3. Press F4 (QUIT)orF3 (MENU) if you change your mind.

4. The meter will automatically return to the measurement screen with new options available for the function keys.

12. % S DT

27.5 MAX CF LOG

MAX

END QUI T

F1 F2 F3 F4

5. Proceed to make measurements as normal. To log the value of the point currently being measured and displayed on the second line of the display, press F1 (LOG).

46 Operating the Meter

6. A screen will appear that indicates the value of reading that has been temporarily stored in memory and the number of the data point. The first data point will be 001.

DATA POINT NO.001

12.1 % STD

SAVE DI SCARD

F1 F2 F3 F4

7. Press F1 (SAVE) to permanently log this data point into the meter’s memory with its associated data point number. The meter will automatically return to the measurement mode.

8. Press F3 (DISCARD) to erase the data point from the meter’s temporary memory. The meter will automatically return to the measurement mode.

9. Press F1 (LOG) again to log the second data point. It will automatically be assigned data point 002 providing that you had saved the first data point. If you had elected to discard the first data point, then this point will be designated data point 001.

10. Press either F1 (SAVE) or F3 (DISCARD). The meter will automatically return to the logged measurements screen.

11. Continue to record up to 999 data points in this manner.

12. To end this logging run and begin a new run, press F3 (END). The screen will appear that allows you to enter another two-digit survey number.

NEW L OGG I NG RUN :

ENTE

OK CLR MENU QU I T

F1 F2 F3 F4

NEW FRNO.__

47Chapter 8 Data Logging

13. Use the numeric keypad to enter a new two-digit survey number and then press F1 (OK)orENTER. Again, make note of this number so that you can later associate this survey number with the data points collected. If you make a mistake, press F2 (CLR)to clear the screen and enter a new survey number. The meter will automatically return to the logged measurements screen.

14. To end logging altogether and return to the standard measurement screen, press F4 (QUIT). To initiate logging again at a later point, use the menu system to select DATA LOG from the First Menu Screen.

Mode 2 Logging

To initiate Mode 2 logging (a series of spatially-averaged data points with a reference number assigned to each data point)...

1. From the main data-logging screen, press the number 2 on the keypad to select LOG AVG WITH REF # from the logging menu screen.

1LOGWITHREF # 2LOGAVGWITHREF# 3 CONT I NUOUS LOGG I NG

MEM QU I T

F1 F2 F3 F4

48 Operating the Meter

Note

It is important to move the probe vertically at a con stant rate to obtain an accurate spa

tially averaged measurement.

NEW L OGG I NG RUN :

ENTE

OK CLR MENU QU I T

F1 F2 F3 F4

NEW FRNO.__

3. Press F4 (QUIT)orF3 (MENU) if you change your mind.

4. The meter will automatically return to the measurement screen with new options available for the function keys.

12.1 % STD

27.5 MAX CF 1.00

START MAXR END QUIT

F1 F2 F3 F4

5. Proceed to make measurements as normal. To initiate making a spatially-averaged measurement that will be logged, hold the meter in one hand and the probe in the other with the head of the probe touching the ground.

6. Press F1 (START) while slowly moving the probe

vertically at a constant rate of movement. Keep your finger on the F1 key during this operation.

7. Strive for an interval of about ten seconds between starting and stopping the timer. The displayed value will flash and the audio signal will sound every second as a timing aid.

8. When the probe reaches the height equal to the top of an adult's head (about 6 ft./1.9 m), press F1 again (STOP).

49Chapter 8 Data Logging

12. % S DT

27.5 MAX CF STOP

F1 F2 F3 F4

9. A screen will appear that indicates the average and maximum values of the reading that has been temporarily stored in memory and the number of the data point. The first data point will be 001.

DATA POINT NO.001

12.1 % STD AVG

27.5 % STD MAX

SAVE DI SCARD

F1 F2 F3 F4

10. Press F1 (SAVE) to permanently log this data point into the meter’s memory with its associated data point number. The meter will automatically return to the logged measurement screen.

11. Press F3 (DISCARD) to erase the data point from the meter’s temporary memory. The meter will automatically return to the logged measurement screen and display real time values.

12. Press F1 (START) again to begin the second spatially averaged data point. It will automatically be assigned data point 002 providing that you had saved the first data point. If you had elected to discard the first data point, then this point will be designated data point 001.

13. Press either F1 (SAVE) or F3 (DISCARD).

14. Continue to record up to 999 spatially-averaged data points in this manner. Both the average and maximum values will be saved and will be associated with a specific data point number.

50 Operating the Meter

15. To end this logging run and begin a new run, press F3 (END). The screen will appear that allows you to enter another two-digit survey number.

NEW L OGG I NG RUN :

ENTE

OK CLR MENU QU I T

F1 F2 F3 F4

NEW FRNO.__

16. Use the numeric keypad to enter a new two-digit survey number and then press F1 (OK)orENTER. Again, make note of this number so that you can later associate this survey number with the data points collected. If you make a mistake, press F2 (CLR)to clear the screen and enter a new survey number. The meter will automatically return to the logged-measurements screen.

17. To end logging altogether and return to the standard measurement screen, press F4 (QUIT). To initiate logging again at a later point, use the menu system to select DATA LOG from the First Menu Screen.

Mode 3 Logging

To initiate Mode 3 logging (a series of data points automatically logged at specific intervals)...

1. From the main data logging screen, press the number 3 on the keypad to select CONTINUOUS LOGGING from the logging menu screen.

1LOGWITHREF # 2LOGAVGWITHREF# 3 CONT I NUOUS LOGG I NG

MEM QU I T

F1 F2 F3 F4

51Chapter 8 Data Logging

NEW L OGG I NG RUN :

ENTE

OK CLR MENU QU I T

NEW FRNO.__

F1 F2 F3 F4

3. A new menu screen will appear that offers five different logging rates: 1/SEC, 10/MIN, 1/MIN, 10/HR, and 2/HR.

LOGGING RATE=10/MIN 1= 1/SEC 4= 10/HR 2= 10/MIN 5= 2/HR 3= 1/MIN OFF

F1 F2 F3 F4

4. Press the number on the numeric keypad (1-5) that corresponds to the desired logging rate.

5. A new menu screen will appear. The numeric keypad and the function keys are used to define the duration of time to be logged.

CONT I NUOUS LOGG I NG

RATE=10 /MIN

DURATION=__SEC/MN/HR

SEC MIN HR CONT

F1 F2 F3 F4

52 Operating the Meter

6. To log for a specific interval of time, enter a two-digit number on the keypad. If you make a mistake entering a number, simply continue entering numbers until the correct value is displayed. Then press either F1 (SEC), F2 (MIN), or F3 (HRS) and the meter will automatically return to the measurement screen with new options available for the function keys.

7. To log for an indeterminate interval of time (until you tell the meter to stop or the memory is filled), press F4 (CONT). The meter will automatically return to the measurement screen with new options available for the function keys.

12.1 % STD

27.5 MAX CF 1.00 LOG MAXR MENU QUIT

F1 F2 F3 F4

8. Proceed to make measurements as normal. To initiate logging, press F1 (LOG). The meter will beep every time a data point is recorded.

12.1 % STD

27.5 MAX CF 1.00 LOG END QUI T

F1 F2 F3 F4

9. If a specific interval of time had been selected, the meter will automatically stop logging at the end of this interval. To stop logging earlier or when set to an indeterminate period of time, press F3 (END).

53Chapter 8 Data Logging

10. A screen will appear requesting that you assign another two digit survey number to the new logging run. Use the numeric keypad to enter the two-digit number and then press F1 (OK)orENTER. Again, make note of the number for later use. If you make a mistake, press F2 (CLR) to clear the screen and enter a new survey number. The meter will automatically return to the logged measurements screen.

NEW L OGG I NG RUN :

ENTE

OK CLR MENU QU I T

F1 F2 F3 F4

NEW FRNO.__

To begin another logging run at a different rate or for a different duration...

Press F3 (MENU). Press the number 1 on the keypad

•

to select DATA LOG from the First Menu Screen and proceed as previously described.

To end logging altogether and return to the standard measurement screen...

•

Press F4 (QUIT). To initiate logging again at a later point, use the menu system to select DATA LOG from the First Menu Screen.

Memory Capacity

To determine the remaining memory of the 8718B meter...

1. Access the menu system by pressing the function key that corresponds to the legend below MENU on the bottom line of the display.

2. Press the number 1 on the keypad to select DATA LOG from the First Menu Screen.

54 Operating the Meter

3. Press F2 (MEM).

4. A screen will appear showing the approximate amount of available memory and the amount of memory already used. The bar graph is a rough indicator of remaining memory capacity as a percentage of total capacity.

AILALB

10 B AVAI

F1 F2 F3 F4

L, 15

MENU QUIT

ORY

SED

Bkk

A record contains a header and one or more data points. To estimate the approximate number of data points and records (logging runs) that can be stored with the available memory ...

1. Allocate 33 bytes for each header. A separate header is used for each record.

2. Allocate 7 bytes for each data point from Mode 1 and Mode 3 logging.

3. Allocate 14 bytes for each for each spatially averaged data point from Mode 2 logging. More memory is used in this mode because both average and peak values are stored.

4. Determine whether there is sufficient available memory to perform the desired task. If there is, proceed with logging as described above.

5. If you determine that there is insufficient memory to perform the desired task because much of the meter’s memory has been used, it will be necessary to empty the memory. Press F4 (QUIT)

6. To download the current memory contents, you must connect the 8718B to a computer. See Chapter 18, User's Software.

55Chapter 8 Data Logging

7. To discard the contents of the meter’s memory once the contents have been downloaded or without saving the information, access the menu system by pressing the function key that corresponds to the legend below MENU on the bottom line of the display.

8. Press 8 (NEXT) to get to the Second Menu Screen.

9. Press 2 (SETTINGS).

10. A new screen will appear offering several options.

SETTINGS 1CLOCK 4RGT/LEFT 2TEMP 5DISPLAY 3CLEARMEMORY

F1 F2 F3 F4

11. Press 3 (CLEAR MEMORY). A screen will appear requesting that you confirm your request and warning that the stored information will be lost.

CLEAR MEMORY CLEAR I NG THE MEMORY CAN NOT BE REVERSED CLEAR ABORT

F1 F2 F3 F4

12. Press F1 (CLEAR) to clear the memory or F1 (ABORT) to return to the First Menu Screen without clearing the memory.

Analog Output

The 8718B Meter allows the user to output a DC voltage that is proportional to the instantaneous measured value. When connected to a typical chart recorder, it will provide a continuous analog record of the measured field strength. See Chapter 17, Operation with a Data Recorder.

56 Operating the Meter

Time-Averaged Measurements

Measurement Options

The 8718B meter features two averaging modes:

Mode 1

Mode 2

Perform fixed-time averaging over any one of several

•

specific time intervals.

Perform averaging to meet the requirements of a

•

specific standard. The averaging period is automatically set by meter.

Making Time-Averaged Measurements

To make time averaged measurements ...

1. Access the menu system by pressing the function key that corresponds to the legend below MENU on the bottom line of the display.

2. Press number 2 on the keypad to select TIME AVG from the First Menu Screen.

3. A new menu will appear offering two averaging modes. The status of both modes will be shown.

T IME AVERAGING 1FIXEDTIME:OFF 2STANDARDS: OFF ENTER NO . TO TURN ON

F1 F2 F3 F4

4. Press F4 (OFF) to turn either time averaging mode off and return to the measurements screen.

57Chapter 9 Time-Averaged Measurements

Mode 1 Averaging

To initiate Mode 1 averaging (fixed time averaging over any one of several specific time intervals)...

1. Press number 1 on the keypad to select FIXED TIME from the averaging menu screen. Selecting Mode 1 averaging will automatically shut off Mode 2 averaging if it is on.

2. A new menu screen will appear that offers four different averaging intervals: 30 SEC, 1MIN, 6MIN, and 30 MIN. If an averaging interval had previously been selected and is currently active, that selection will be flashing.

F IXED T IME AVERAGING 1=30 SEC 3= 6 MIN 2= 1 MIN 4=30 MIN

OFF

F1 F2 F3 F4

3. Press the number on the numeric keypad (1-4) that corresponds to the desired averaging interval and the meter automatically returns to the measurement screen with new options available for the function keys. If you had accessed the menu system from the Opening Menu Screen, you will return to that screen.

12.1 % STD

27.5 MAX CF 1.00 START MENU QUI T

F1 F2 F3 F4

4. At any time you can press F4 (QUIT) to turn the time averaging mode off and return to the normal measurements screen.

58 Operating the Meter

5. The meter will continue to make real-time measurements until you initiate making the timeaveraged measurement.

6. Determine where you want to make the averaged measurement and place or hold the probe in the desired position. For short intervals, it may be practical to hold the meter in one hand and the probe in the other. For longer intervals, it is suggested that you place the probe on some form of non-conductive stand so that it does not move. At frequencies above 50 MHz, the meter should be separated from the probe by a minimum of 12 inches (30 centimeters) to minimize any interaction between the meter, the probe, and the electromagnetic field. At the lower frequencies, the measurement techniques are very different. See Low Frequency Measurements in the Applications Booklet.

7. Press F1 (START) when you are ready to begin the time-averaged measurement.

8. The averaged value is displayed on the screen and will flash each time it is updated (one second intervals). The meter will automatically stop at the end of the selected averaging interval.

9. To end time averaging prior to the end of the averaging interval, press F4 (STOP).

24 . 2 % STD AVERAGE

39.5 MAX CF 1.00 PAUSE STOP

F1 F2 F3 F4

10. At the end of the averaging interval, the meter will show the time-averaged value and the averaging interval on the second line of the display. The maximum value will be shown on the third line of the display. The bar graph will be indicating the instantaneous field strength in real time.

59Chapter 9 Time-Averaged Measurements

Note

If you access the menu system from the Opening Menu Screen, you will re turn to that screen. Once a probe has been selected and zeroed, the mea surement screen will reflect the averaging mode that you have selected.

24. % S DT

39.5 MAX 10 TSART

F1 F2 F3 F4

CLR

ERAGE

SEC

MENU QU I T

11. To make another time-averaged measurement over the same interval, press F1 (START) again.

12. To temporarily suspend the time average mode (once the current measurement interval has been completed or stopped) and make real time measurements, press F2 (CLR). To make another time-averaged measurement over the same interval, press F1 (START) again.

13. To end time averaging altogether and return to the standard measurement screen (once the current measurement interval has been completed or stopped), press F4 (QUIT). To initiate time averaging again at a later point, use the menu system to select TIME AVG from the First Menu Screen.

To temporarily pause during a time-averaged measurement...

1. To temporarily suspend time averaging, press F3 (PAUSE). The word *PAUSED* will appear on the fourth line of the display. To resume time averaging and complete the measurement, press F1 (START).

24 . 2 % STD AVERAGE

39.5 MAX CF 1.00

START *PAUSED * STOP

F1 F2 F3 F4

60 Operating the Meter

Note

2. You may continue to pause and start the averaging as many times as needed. The time interval initially selected applies only to the measurement time.

The PAUSE feature can be useful when measuring the aver age value from cer tain rotating radars. The effective mea surement technique requires you to pause during the pe riod of time when you are not in the beam of the radar. Continue this technique for two or more revolutions (depending on the RPM) to obtain a realistic average value of the field in the beam at your location. For details on this measurement technique, see Radar Measurements in the Applications Booklet.

3. To end time averaging while *PAUSED*, press F4 (STOP).

To change the averaging interval...

1. To change the averaging interval (once the current measurement interval has been completed or stopped), press F4 (QUIT). To initiate a new time

averaging interval, use the menu system to select TIME AVG from the First Menu Screen.

2. Proceed as previously described to select FIXED TIME from the averaging menu screen and then the new averaging interval.

Mode 2 Averaging

Mode 2 averaging (time averaging to meet the requirements of a specific standard) requires two parameters to be properly set before being used:

•

The meter must be set to the correct standard for your application.

•

The meter must be set for a specific frequency because the averaging time in many standards is frequency dependent. For example, IEEE C95.1-1999 specifies a six minute averaging period for Controlled Environments from 3 kHz to 15 GHz. Above 15 GHz, the averaging period decreases to ten seconds at 300 GHz based on a logarithmic function.

61Chapter 9 Time-Averaged Measurements

To set the meter for a specific frequency...

1. Press F4 (FREQ) from the measurement screen. A new screen will appear to allow you to enter a frequency.

FREQUENCY : __ . __ GH

CORRECT. FACTOR:1.00

Hkz z z MH GH SAVE

F1 F2 F3 F4

2. Enter the frequency that you want to use for the timeaveraged measurements. Make sure you fill in all four positions. If you make a mistake just enter more digits until correct. For greater accuracy, use the units that allow the larger number. For example, enter

10.00 kHz, not 00.01 MHz.

3. Change the units (if needed) by pressing either F1 (kHz), F2 (MHz), or F3 (GHz).

4. Press F4 (SAVE). The meter will automatically return to the measurement screen.

5. If the probe used is a probe in memory, the frequency that you have set will be displayed on the right side of the third line of the display. The meter will also automatically correct the readings for probe frequency deviation. The meter does this by using the closest calibration frequencies above and below the selected frequency to calculate and apply an appropriate correction factor. This new correction factor is briefly shown on the second line of the display after you press F4 (SAVE) before the meter automatically returns to the measurement screen.

62 Operating the Meter

To initiate Mode 2 averaging (averaging to meet the requirements of a specific standard)...

1. Make sure that the meter is set for the correct standard or change it if needed. See Chapter 11, Using the Standards Feature.

2. Make sure the meter is set to the correct frequency for the measurement you are making. See page 64.

3. Press number 2 on the keypad to select STANDARDS AVG from the averaging menu screen. Selecting Mode 2 averaging will automatically shut off Mode 1 averaging if it is on.

4. A new screen will appear stating that averaging has been enabled in accordance with a specific standard.

AVERAGI NG ENABLED STND: IEEEC95.1-1999 LEVEL : CONTROLLED BEGI N CANCEL OFF

F1 F2 F3 F4

5. Press F3 (CANCEL) to return to the initial time averaging menu screen to make another selection or press F4 (OFF) to turn time averaging off and return to the standard measurement screen.

6. Press F1 (BEGIN) to automatically return to the measurement screen with new options available for the function keys.

6.26 Wmcm/

11.5 MAX 10.00 GHz START MENU FREQ QUI T

F1 F2 F3 F4

63Chapter 9 Time-Averaged Measurements

7. The meter will continue to make real time measurements until you initiate making the timeaveraged measurement.

8. Press F1 (START) when you are ready to begin the time-averaged measurement.

9. The averaged value is displayed on the screen and will flash every second each time it is updated. The meter will automatically stop at the end of the averaging interval, which was determined by the standard and the frequency.

10. To end time averaging prior to the end of the averaging interval, press F4 (STOP).

Note

8.71 Wmcm/

11.

MAX 10.00 GHz

P AUSE STOP

AVERAGE

F1 F2 F3 F4

11. At the end of the averaging interval, the meter will show the time-averaged value on the second line of the display and the maximum value on the third line of the display. The bar graph will be indicating the instantaneous field strength in real time.

8.71 mW/c m2 AVERAGE

11.5 MAX 10.00 GHz

START CLR MENU QUI T

F1 F2 F3 F4

12. To make another time-averaged measurement at the same frequency, press F1 (START) again.

64 Operating the Meter

Note

The PAUSE feature can be useful when measuring the aver age value from cer tain rotating radars. The effective mea surement technique requires you to pause during the pe riod of time when you are not in the beam of the radar. Continue this tech nique for two or more revolutions (depending on the RPM) to obtain a realistic average value of the field in the beam at your location. For details on this measurement technique, see Radar Measurements in the Applications Booklet.

13. To temporarily suspend the time average mode (once the current measurement interval has been completed or stopped) and make real time measurements, press F2 (CLR). To make another time-averaged measurement under the same conditions, press F1 (START) again.

14. To end time averaging altogether and return to the standard measurement screen (once the current measurement interval has been completed or stopped), press F4 (QUIT). To initiate time averaging again at a later point, use the menu system to select

To temporarily pause during a time averaged

TIME AVG from the First Menu Screen.

measurement...

1. To temporarily suspend time averaging, press F3 (PAUSE). The word *PAUSED* will appear on the fourth line of the display. To resume time averaging and complete the measurement, press F1 (START).

8.71 mW/c m2 AVERAGE

11.5 MAX 10.00 GHz START *PAUSED* STOP

F1 F2 F3 F4

2. You may continue to pause and start the averaging as many times as needed. The time interval determined by the standard and the frequency applies only to the measurement time (excludes time when "PAUSED").

3. To end time averaging while *PAUSED*, press F4 (STOP).

65Chapter 9 Time-Averaged Measurements

To change the frequency...

1. To change the frequency (once the current measurement interval has been completed or stopped), press F2 (CLR) if the averaged value is displayed.

2. Once the meter is displaying real time values, the frequency menu is accessed by pressing F3 (FREQ).

3. Proceed as previously described to set the meter to a new frequency.

66 Operating the Meter

Note

If you access the menu system from the Opening Menu Screen, you will return to that screen. Once an alarm set ting has been made, the alarm function will be initiated once the meter is placed into the measure ment mode.

Alarm Settings

Alarm Description

The Model 8718B Meter is equipped with an audible alarm that emits sound through a tiny hole on the bottom of the meter. The alarm sounds automatically whenever the field strength exceeds the measurement range of the probe or over ranges.

The meter can also be set to sound its alarm at a specific level and/or to sound a variable tone indication of field strength.

Controlling the Alarm Functions

To make changes to the audio alarm settings...

1. Access the menu system by pressing the function key that corresponds to the legend below MENU on the bottom line of the display.

2. Press 8 (NEXT)togototheSecond Menu Screen.

3. Press 5 (ALARM) to access the alarm menu. A new menu will appear that allows you to:

•

Turn the audio alarm on or off.

•

Set the alarm threshold in terms of percent of full scale of the probe in use (1% to 99%).

•

Turn the variable tone alarm on or off.

AUD IO ALARM SETT I NGS

FIXED IS TONE IS

ON @ 25% OFF

ON OFF ON OFF

F1 F2 F3 F4

67Chapter 10 Alarm Settings

Note

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 frequency 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.

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

5. The right side of the display indicates whether the

6. The bottom line of the display indicates which function

Fixed Alarm

1. Use F1 (ON)orF2 (OFF) to change the status of the

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

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

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

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%).

variable tone alarm is either on or off.

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

fixed 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 has a full scale measurement range of 20 mW/cm

when using a Model 8721D probe, which

, set

the alarm threshold to 25%.

that next. See Variable Tone Alarm on the following page.

ENTER and the meter will return to the measurement screen.

68 Operating the Meter

Variable Tone Alarm

1. Use F3 (ON)orF4 (OFF) to change the status of the fixed alarm. The variable tone alarm constantly generates a series of tones that increase in frequency in direct proportion to field strength.

Note

The fixed and vari able tone alarms op erate independently of each other. The meter can be set to have both alarms off, either one of the alarms on, or both alarms on. If both alarms are turned on, the variable tone rate will vary with the field strength unless the measured field strength exceeds the fixed alarm threshold. The alarm will then sound a continuous tone.

2. If you want to turn the fixed alarm on or off, do that next See Fixed Alarm on the previous page.

3. When you are satisfied with all the alarm settings,

press ENTER and the meter will return to the measurement screen.

69Chapter 10 Alarm Settings

70 Operating the Meter

Using The RF Exposure Standards Feature

Application

The Model 8718B Meter is always set to reference a particular safety standard, regulation, or guidance.

The 8718B uses the referenced standard in two ways:

The Alternate Measurement Display Screen displays

•

additional information about the instantaneous measurement at a particular frequency. See Alternate Measurement Display Screen on page 20.

Time-averaged measurements are made to conform to

•

the referenced standard at the specified frequency.

Checking or Changing the Standard

To determine which standard the 8718B is currently set to reference ...

1. Access the menu system by pressing the function key that corresponds to the legend below MENU on the bottom line of the display.

2. Press number 8 (NEXT) to select the Second Menu Screen.

3. Press number 6 to select STNDS.

4. A screen will appear that specifies the current standard. The specific level or tier will be specified for standards with more than a single tier.

71Chapter 11 Using the RF Exposure Standards Feature

Note

IEEE C95.1-1999

CONTROLLED ENVIR

Many standards have more than one tier, i.e., IEEE C95.1-1999 establishes different Maximum Permissi ble Exposure (MPE) levels and averaging times for Controlled Environments and for Uncontrolled Envi ronments.

OK STNDS

F1 F2 F3 F4

5. Press F1 (OK) to continue using this standard as a reference without change.

To change the standard or tier that the 8718B references...

6. Press F4 (STNDS). A new menu screen will automatically appear that lists several major international standards.

1FCC‘97 5 IRPA 2 I EEE ‘ 99 6 US DOD 3 ANS I ‘ 82 7 UK 4ACGIH 8NEXT

F1 F2 F3 F4

7. Press the number on the keypad that matches the desired standard.

For standards with only a single tier...

8. A new screen will appear that lists the complete standard number.

ANSI C95.1-1982

OK STNDS

F1 F2 F3 F4

72 Operating the Meter

9. Press F1 (OK) to begin using this standard as a reference.

10. Alternately, press F4 (STNDS) to select another standard.

For standards with two or three tiers...

11. A new screen will appear that lists the complete standard number at the top of the display. The available tiers will be listed below the basic standard.

Note

Changing the level referenced on a multi-tier standard does NOT change the characteristics of a probe ie. a probe rated at 600% of occupational limits always yields an output in Percent of the Occupational limits.

FCC REGULAT IONS ' 97 1 OCCUPA ' L /CONTRL 'D 2 GEN POP /UNCONTR ' D

ENTER NO. TO SELECT

F1 F2 F3 F4

12. Press the number on the keypad that matches the desired tier. The screen will change so that only the standard and the selected tier are shown with two options available for the function keys.

FCC REGULAT IONS ' 97

OCCUPA ' L /CONTRL 'D

OK STNDS

F1 F2 F3 F4

13. Press F1 (OK) to begin using this standard and tier as a reference.

14. Alternately, press F4 (STNDS) to select another standard.

73Chapter 11 Using the RF Exposure Standards Feature

74 Operating the Meter

Back Light and Battery Status

Application for Back Light

The liquid crystal display (LCD) on the Model 8718B Meter provides high contrast in bright outdoor lite. However, LCD’s do not generate any light and can be difficult to read in low light conditions. The LCD on the 8718B contains a high brightness back light that can be turned on whenever it is needed.

The only disadvantage to using the back light is that it consumes much more energy than the meter circuits and significantly reduces operating time between battery charges.

Controlling the Back Light

To turn the back light on or off...

1. Access the menu system by pressing the function key that corresponds to the legend below MENU on the bottom line of the display.

2. Press 4 to select BAT/LITE from the First Menu Screen. A new screen will appear that indicates both battery status and back light status.

BATTERY GHT LEVEL= 90% l IS OFF TIME=18HRS lON OFF

F1 F2 F3 F4

3. Press F3 (ON)orF4 (OFF) to turn the back light on or off as required.

4. Press the ESC key to return to the First Menu Screen. Press it again to return to the measurements screen.

75Chapter 12 Back Light and Battery Status

Battery Capacity

The Model 8718B Meter uses a custom rechargeable battery. Under normal conditions, the battery provides about 20 hours of use before it must be recharged. The two features on the 8718B that significantly increase the current draw and therefore reduce the operating time are the back light and the RS232 serial port. It is for this reason that the default condition upon turn-on for both these features is off. Operating time with the back light on is about 6.5 hours. This is normally sufficient for a full day of measurements but it is a factor that must be considered.

Checking Battery Status

To check the battery status...

1. Access the menu system by pressing the function key that corresponds to the legend below MENU on the bottom line of the display.

2. Press 4 to select BAT/LITE from the First Menu Screen. A new screen will appear that indicates both battery status and back light status.

BATTERY GHT LEVEL= 90% l IS OFF TIME=18HRS lON OFF

F1 F2 F3 F4

3. The bar graph indicates the approximate charge level of the battery. The charge level is also shown as a numerical percentage on the left side of the third line of the display.

The estimated operating time under the current operating conditions is shown on the left side of the bottom line of the display. Turning the back light on, for example, reduces the operating time significantly.

76 Operating the Meter

4. Press the ESC key to return to the First Menu Screen. Press it again to return to the measurements screen.

Accuracy of Battery Status Indicator

The characteristics of Ni-Cad rechargeable batteries make it difficult to provide a truly accurate indication of charge level. This is because there is very little voltage difference over a broad range of charge levels.

The battery status indicator on the 8718B is reasonably accurate when indicating charge levels of more than 80% or less than 20%. Unfortunately, indicated charge levels greater than 20% but less than 80% are only very rough estimates.

It is a characteristic of these batteries to get a large voltage increase with only a brief charging period if one starts with a battery that is completely discharged. However, under such conditions, the battery has very little capacity and the voltage drops quickly in use. Since the status indicator circuits measure battery voltage, this can lead to erroneous indications of charge level when the meter is first turned on. This false indication will only occur when the batteries do not receive a complete charge.

The battery should be charged for a minimum of eight hours, but ideally only when the status indicator shows a level of less than 20%. The back light can be turned on to speed up the discharge process when desired. These batteries obtain a maximum charge when charging takes place with batteries close to fully discharged.

77Chapter 12 Back Light and Battery Status

78 Operating the Meter

Keypad Lockout and

Display Blanking

Description

The Lockout feature disables the keypad to prevent inadvertent changes in operation. This feature can be useful while climbing and/or if the meter is left unattended during a long data logging session.

The Blank feature both disables the keypad and blanks the display. This feature can be useful if the meter is left unattended during a long data logging session.

Keypad Lockout

To lock the keypad...

1. Access the menu system by pressing the function key that corresponds to the legend below MENU on the bottom line of the display.

2. Press number 8 (NEXT) to select the Second Menu Screen.

3. Press 4 to select LOCKOUT.

4. The meter will automatically return to the measurements screen and the keypad will be locked. Only the Off key will respond to commands individually.

To unlock the keypad...

5. Simultaneously depress both the Enter and Esc keys to unlock the keypad. These are the two dark blue keys.

79Chapter 13 Keypad Lockout and Display Blanking

Display Blanking and Keypad Lockout

To both blank the display and lock the keypad...

1. Access the menu system by pressing the function key that corresponds to the legend below MENU on the bottom line of the display.

2. Press number 8 (NEXT) to select the Second Menu Screen.

3. Press 7 to select BLANK.

4. The meter will automatically return to the measurements mode but will be blank. The keypad will also be locked. Only the Off key will respond to commands individually.

To both activate the display and unlock the keypad...

5. Simultaneously depress both the Enter and Esc keys to both activate the display and unlock the keypad. These are the two dark blue keys.

80 Operating the Meter

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.

12. % S DT

27.5 MAX A LT MAXR MENU FREQ

F1 F2 F3 F4

81Chapter 14 Probe Zero

Causes of Zero Drift

All sensors have a change in output that is a function of temperature. In a probe, it is both the thermal coefficient of the detector and the gain of the probe amplifier that determine how much a probe drifts over temperature. Thermal compensation circuitry in the probe is used to minimize the impact of temperature change. Thermocouple detectors have the lowest thermal coefficient but their very low level output requires much more amplifier gain than diode sensors, especially in electric field probes. Therefore, Narda probes with the greatest amount of thermal drift are the microwave- band electric field probes, which all use thermocouple sensors. The lower frequency electric field probes use diodes and require much less gain. Narda magnetic field probes use thermocouples but the circuit requires lower gain than the electric field probes.

The other possible cause of zero drift can occur when a probe is subjected to a very high field level and then is moved to an area with a very low field. The high field heats the sensor and can cause drift. However, this type of drift normally corrects itself within a few minutes.

Many competitive diode sensor probes exhibit drift for another reason - reaction to infrared light on the diodes. Narda probes do not have this problem. Narda uses special diodes with an integral light shield, photographic paper inside the probe cover, and a combination anti-static shield and blackout coating on the inside of the probe cover.

Checking for Zero Drift

There are two indications that the probe may have drifted enough to require correction.

•

Whenever the negative zero drift exceeds 0.1% of full scale of the probe, the words “RE-AUTO-ZERO” will flash on the top line of the display. This will replace the bar graph.

82 Operating the Meter

RE- AUTO- ZERO

12.1 % STD

27.5 MAX CF 1.00 ALT MAXR MENU FREQ

F1 F2 F3 F4

Whenever the meter continues to show low-level values

•

and never seems to get back to a zero-field condition, positive zero drift is a possibility. This can be confirmed by shielding the probe to see if the meter goes back to a zero reading. See Shielding the Probe on the following page for suggested methods.

Temperature Concerns

It is important to allow the meter and probe to become conditioned to the ambient temperature before attempting to zero the system. This is especially important when the meter and probe have been transported or stored at a different temperature such as in a vehicle, for example. Diode sensor-based probes require only a few minutes to stabilize. The thermo-couple sensors used in microwave band and ultra broadband probes may require 15-20 minutes to stabilize.

Establishing a Zero Field

It is important to “zero” the probe while the probe is not exposed to a significant RF field level. For accuracy, the field level should be lower than the lowest value that the probe is capable of reading. If previous measurements have indicated that the ambient field level is very low, the probe can be zeroed without shielding. This is often the case in a typical office environment. It is recommended that the ambient field level be at least 30 dB below the full scale measurement range of the probe. When it is necessary to zero a probe in higher field areas, the probe must be shielded.

83Chapter 14 Probe Zero

Note

The Electric Field At tenuator can not be used to zero mag netic field probes.

Shielding the Probe

The probe must be shielded from significant RF fields whenever it is zeroed with the meter. This is to establish a zero reference for the field.

There are four ways to shield the probe during zeroing:

Use the Model 8713B Electric Field Attenuator supplied

•

with the meter. This conductive fabric is the same material that is used in RF protective clothing. The

attenuator should be put over the head of the probe and closed off around the neck of the probe above the handle using the hook-and-loop fastener band.

Use the shielded storage case. Place the probe in the

•

case and close the lid carefully on the cable with the meter outside the case. Be careful not to move the probe while zeroing takes place (On probes with low frequency test points you can create static which will give inaccurate results, although this is less of a concern with the new 8700D series probes).

• Use aluminum foil to shield the head of the probe. Fully

wrap the head of the probe and close it around the neck of the probe about half way down. If the probe has metallic low frequency test points, these must be insulated from the aluminum foil. One way to do this is to use electrical tape to cover the test points. The other solution is to use a wide elastic band around the head of the probe over the test points. The elastic band can easily be moved to use the 8718B’s built-in low frequency RF test source. Alternately, use an aluminum can.

•

Use your body to shield the probe from the source of energy.

84 Operating the Meter

Zeroing the Probe While In Use

The meter and probe are initially zeroed before the meter is allowed to go into the measurement mode. If you determine that significant drift may have occurred, it is simple to fine tune the zero. See Checking for Zero Drift on page 82.

To zero the probe while in use...

1. Shield the probe using one of the methods described in Shielding the Probe.

2. Press the Auto Zero key. The meter will correct for any

probe drift in about eight seconds. The meter will then automatically return to the measurements screen.

85Chapter 14 Probe Zero

86 Operating the Meter

Advanced Settings

Description

The Settings menu is used to control several features of the Model 8718B that need to be accessed infrequently. The options available under the Settings menu are:

Check or set the meter’s internal clock (time/date).

•

Enter a value for temperature. This feature is used only

•

when the probe is separated from the meter and operating at a different ambient temperature.

Clear the memory of logged data.

•

Set the function keys for right or left handed operation.

•

Adjust the contrast of the display.

•

Accessing the Settings Menu

To access the Settings menu...

1. Access the menu system by pressing the function key that corresponds to the legend below MENU on the bottom line of the display.

2. Press 8 (NEXT) to select the Second Menu Screen.

3. Press 2 to select SETTINGS. A new screen will appear that offers five choices.

SETT INGS 1CLOCK 4RGT/LEFT 2TEMP 5DISPLAY 3CLEARMEMORY

F1 F2 F3 F4

87Chapter 15 Advanced Settings

Setting the Clock

To check and/or change the time and date...

1. Access the settings menu by following the procedure described in Accessing the Settings Menu.

2. Press 1 to select CLOCK. A new screen will appear that displays the time on the left side of the screen and the date on the right. The time is in 24 hour format, i.e. 13:30 equals 1:30 P.M. The date format is MM/DD/YY.

TIME IS DATE IS

13:42 02/27/98

2 4HR - FORMAT - MM/ DD / YY

SET SET

F1 F2 F3 F4

3. Press the Esc key to return to the First Menu Screen without making any changes.

To set the time...

1. Press F1 (SET). The display will change to show four underscored lines where the new time must be entered.

TIME IS DATE IS

__:__ 02/27/98

2 4HR - FORMAT - MM/ DD / YY

SAVE

F1 F2 F3 F4

2. Enter the new time in 24-hour format using the numeric keypad. If you make a mistake, simply enter more numbers until the correct time has been entered.

3. Press F2 (SAVE) to save the new time.

88 Operating the Meter

4. Proceed to setting the date, if required.

5. Alternately, press the Esc key to return to the First Menu Screen. Press Esc again to return to the measurements screen.

To set the date...

1. Press F3 (SET). The display will change to show six underscore lines where the new date must be entered.

TIME IS DATE IS

13:42 __/__/__

24HR -FORMAT -DD /MM/ YY

SAVE

F1 F2 F3 F4

2. Enter the new date in DD/MM/YY format using the numeric keypad. If you make a mistake, simply enter more numbers until the correct time has been entered.

3. Press F4 (SAVE) to save the new time.

4. Proceed to setting the time, if required.

5. Alternately, press the Esc key to return to the First Menu Screen. Press Esc again to return to the measurements screen.

Temperature Correction

This feature is only used when the meter and probe are operating at significantly different ambient temperatures.

This situation can occur when the meter is located indoors and the probe is outdoors. Either a probe extension cable or a fiber optic link system is normally used for such applications. Temperature correction circuitry is used in the probe and there is a temperature sensor located inside the meter. To achieve the highest level of accuracy, it is important that the sensor inside the meter sense the ambient temperature that the probe is subjected to. If the two components are operating in different ambient temperature environments, the 8718B can be set to

89Chapter 15 Advanced Settings

correct for the temperature differential. The amount of error that can occur when the meter and probe are operating at different temperatures depends on the particular probe design as well as the temperature differential. The maximum error that can occur is about 1% per degree Centigrade for diode probes and about

0.1% per degree Centigrade for thermocouple probes. The change may either increase or decrease the meter reading from the true value, depending on the probe model.

To correct for a significant temperature differential...

1. Access the settings menu by following the procedure described in Accessing the Settings Menu.

2. Press 2 to select TEMP. A new screen will appear that shows the current mode. The default mode is Auto Correct.

TEMP. CORRECT ION

IS SET FOR AUTO

OK SET

F1 F2 F3 F4

3. Press F1 (OK) to continue with the same setting without change.

4. Press F4 (SET) to either set or change to a specific probe temperature.

5. If the meter was set for a specific temperature and you want to return to the auto correct mode, press F1 (AUTO).

6. A new screen will appear that shows two underscored lines where the probe ambient temperature should be entered. Use the numeric keypad to enter the temperature of the probe in degrees Centigrade.

TEMP. CORRECT ION

IS SET FOR __°C

AT THE PROBE

AUTO SAVE

F1 F2 F3 F4

90 Operating the Meter

Note

All data will be lost when the memory is cleared.

7. Once the correct probe temperature is displayed on the screen, press F4 (SAVE). The meter will automatically return to the measurements screen.

8. Alternately, press F1 (AUTO) to return to the default auto correct mode.

Clearing the Memory

If you determine that there is insufficient memory available to perform the desired logging task because much of the meter’s memory has been used, it will be necessary to empty the memory. All data will be lost when the memory is cleared.

To download the current memory contents prior to clearing the memory you must connect the 8718B to your computer. See Chapter 18, User's Software.

To clear the memory...

1. Access the settings menu by following the procedure described in

2. Press 3 (CLEAR MEMORY). A screen will appear

requesting that you confirm your request and warning that the stored information will be lost.

Accessing the Settings Menu.

CLEAR MEMORY CLEAR I NG THE MEMORY CAN NOT BE REVERSED CLEAR ABORT

F1 F2 F3 F4

3. Press F1 (CLEAR) to clear the memory or F4 (ABORT) to return to the First Menu Screen without clearing the memory. Press Esc to return to the measurements screen.

91Chapter 15 Advanced Settings

Function Key Position

The position of the commands for the function keys (F1-F4), as described in this guide, is for right-hand operation. Conventionally, right-handed people hold the probe in their right hand and the meter in their left hand. The choice of function key location for the START and LOG commands is particularly important because it is often desirable to press these keys without looking at the meter. This situation occurs during spatial averaging, data logging, and time averaging.

The four function keys on the Model 8718B allow for easy operation with your thumb and the raised area around each key makes it easy to be certain that your thumb is in the correct location. The START and LOG functions are always operated with the F1 key for right-hand operation.

The 8718B allows you to change to left-handed operation with a few keystrokes. When set for left-handed operation, the START and LOG functions will be operated with the F4 key. The functions normally associated with the F4 key are then operated with the F1 key. The meter will remain set the same way upon turn-on and can only be changed by following the procedure described below.

To check or change the function key location...

1. Access the settings menu by following the procedure described in Accessing the Settings Menu.

2. Press 4 to select RGT/LEFT. A new screen will appear that shows the current mode.

FUNCT ION KEYS ARE

SET FOR R I GHT - HANDED

OPERAT ION

OK LEFT

F1 F2 F3 F4

92 Operating the Meter

3. Press F1 (OK) to continue with the same setting without change. The meter will return to the First Menu Screen. Press Esc to return to the measurements screen.

4. Press F4 (LEFT)orF4 (RGT) to change to the alternate setting for function key menu position. The meter will return to the first menu screen. Press Esc to return to the measurements screen.

Adjusting the Display Contrast

The LCD display is set at the factory for the best contrast under typical conditions. The user can adjust the contrast to optimize visibility under specific lighting conditions.

To adjust the display contrast...

1. Access the settings menu by following the procedure described in Accessing the Settings Menu.

2. Press 5 to select DISPLAY. A new screen will appear that shows the current setting. The adjustment range is from 0-9, with 0 the lightest setting and 9 the darkest setting.

DI SPLAY CONTRAST

CURRENT SET NGT:6

0=LIGHT 9=DARK

OK SET

F1 F2 F3 F4

3. Press F1 (OK) to continue with the same setting without change. The meter will return to the First Menu Screen. Press Esc to return to the measurements screen.

93Chapter 15 Advanced Settings

4. Press F4 (SET) to change the display contrast setting. The screen will change to show both the current setting and display an underscore where the new setting is entered.

DI SPLAY CONTRAST

OLD SETT G:I6 NEW SETT ING: _

F1 F2 F3 F4

SAVE

5. Use the numeric keypad to enter a single digit from 0-9 with 0 for the lightest setting and 9 the darkest setting. The contrast will change as soon as the numeric value is entered. You may continue to experiment as many times as needed by entering a new value.

6. When you are satisfied with the setting, press F4 (SAVE). The meter will return to the First Menu Screen. Press Esc to return to the measurements screen.

94 Operating the Meter

Operation with a Fiber Optic Link

Description

Narda fiber optic link transmitters are compatible with all 8700 series probes and the Model 8718B meter. The meter has a built-in fiber optic receiver compatible with the HP Versatile Link type plastic cables and connectors. The fiber optic transmitter connects directly or via a short cable to the probe. A fiber optic cable connects the 8718B to the transmitter.

The transmitter contains a rechargeable battery that provides both power for its own circuitry and to operate the amplifier in the probe. Full system calibration is maintained because each of the components in the system – meter, fiber optic transmitter, and probe – are independently calibrated. The fiber optic transmitter converts the analog DC voltage out of the probe amplifier to a series of pulses. The pulse rate is directly proportional to the probe output.

Application

The fiber optic link provides total isolation between the meter and the probe which is often desirable when making low frequency measurements. At frequencies below 50 MHz, and especially below 10 MHz, there is significant interaction between the field, the individual making the measurements, and the survey equipment. There is also the possibility that the probe and meter will be at different electrical potentials which can result in a false indication of what is actually a scalar field. See Low Frequency Measurements in the Applications Booklet for additional information.

95Chapter 16 Operation with a Fiber Optic Link

The fiber optic link system also allows the meter and probe to be separated by up to 50 meters. One application is surveying towers. A skilled climber carries the probe while the person actually making the measurements remains on the ground.

Controls and Indicators

The fiber optic transmitter has the following controls and indicators:

Control Function Indication

BAT Test

S1 OFF

Tests Battery Charge

Turns Battery Off

Turns Power On

LED On

LED Off

CAL 1

S2 NORM

CAL 2

a. The battery is considered charged when above 15.0 Vdc.

Tests Channel 1

Normal Operation

Tests Channel 2

Meter mid-scale

Variable Level

Above mid-scale

Setting the Meter

The meter has two input ports to receive information from probes:

•

The standard probe cable input

•

The fiber optic receiver input

Only one input can be in use at any time. The default input upon turn-on is the last input port used. It is important to remember this if you switch back and forth between using the standard input and the fiber optic receiver.

96 Operating the Meter

To set the meter to use the fiber optic receiver input...

1. Access the menu system by pressing the function key that corresponds to the legend below MENU on the bottom line of the display.

2. Press 8 (NEXT) to select the Second Menu Screen.

3. Press 3 to select CABLE/FO. A new screen will appear that shows the current input status.

PROBE INPUT STATUS

CABLE ON:

FIBER OPTIC: OFF

OK FO

F1 F2 F3 F4

4. Press F1 (OK) to continue with the same input without change. The meter will return to the First Menu Screen. Press Esc to return to the measurements screen.

5. Press F4 (FO) to change to the fiber optic receiver input. The meter will return to the First Menu Screen. Press Esc to return to the measurements screen.

To set the meter to use the cable input...

6. Access the CABLE/FO menu as previously described. A screen will appear that shows the current input status.

PROBE INPUT STATUS

CABLE OF:F

FIBER OPTIC: ON

OK CABLE

F1 F2 F3 F4

7. Press F1 (OK) to continue with the same input without change. The meter will return to the First Menu Screen. Press Esc to return to the measurements screen.

97Chapter 16 Operation with a Fiber Optic Link

8. Press F4 (CABLE) to change to the cable input. The meter will return to the First Menu Screen. Press Esc to return to the measurements screen.

System Checks

To insure that the entire system – meter, fiber optic transmitter, and probe – are functioning properly...

1. Set the 8718B to use the fiber optic receiver input as previously described.

2. Connect the probe to the fiber optic transmitter.

3. Connect a fiber optic cable between the meter and the fiber optic transmitter.

4. Check the battery charge level in the transmitter by turning switch S1 (BATT TEST–ON)toBATT TEST. Verify that the green LED is illuminated which signifies that the battery is adequately charged for operation. If the LED fails to illuminate, charge the transmitter overnight. A full-battery charge takes approximately 16 hours.

5. Set S1 to the ON position and S2 to the NORM position.

6. Zero the 8718B using the standard procedure.

7. Move S2 ( CAL1–NORM–CAL2) to the CAL1 position. The meter should read 45-55% of the full scale rating of the probe. The actual error from the combination of the 8718B and the fiber optic transmitter is less than (±3%).

8. Move S2 to the CAL2 position. The meter should read approximately 25% higher than the CAL1 position. The exact value is not critical.

9. Set S2 to the NORM position to begin making measurements providing that all the system checks were successfully completed.

98 Operating the Meter

Operation with a Data Recorder

Description

The Model 8718B provides an output signal that can be connected to a data recorder to provide a continuous record of measurement over an extended period of time. The recorder output is available via the smaller of the two jacks located on the left side of the meter. The output is always on.

Output Level

The recorder output ranges from 0.0 volts to 3.0 volts. The level corresponds directly with the indication on the bar graph of the display. Under normal conditions, the bar graph is in the AUTO mode which results in the bar graph using three 10 dB ranges to cover the entire dynamic range of the probe, which is typically 30 dB. Thus, the recorder output would produce a sawtooth pattern if the measured field strength was slowly increased in a linear fashion over the entire dynamic range of the probe. For example, the recorder output level with the 8718B bar graph range set to AUTO used with a probe with a full-scale measurement range of 100 mW/cm, such as the Model 8723D, would follow the table on the next page.

99Chapter 17 Operation with a Data Recorder

NARDA 8718B User Manual

Specifications and Main Features

Frequently Asked Questions

User Manual

Introduction

About the Model 8718B

Getting Started with the Model 8718B

User’s Guide Updates

Equipment Supplied

Using this Guide with a Model 8718

Understanding Your Model 8718B

General Description

Battery Charger and Power Cord

Probe Connection

Audio Alarm

Probe Test Sources

Strap and Tripod Mount

Operation With a Computer

Operation With a Recorder

Keypad

Power Keys

Function Keys

Numeric Keypad

Special Function Keys

Probe Selection

Introduction

Key Factors in Selecting a Probe

Shaped Frequency Response Probes

Connecting a Probe

Probe Identification

Making a Measurement

Introduction

Getting Started

Entering the Probe Model

Zeroing the Probe

Measurement Display Screens

Alternate Measurement Display Screen

Bar Graph Ranges

Testing the Probe

Using Probe Correction Factors

Checking or Changing the Probe Model

Measurement Uncertainty

Making a Measurement

Precautions

Using the Menu System

General

First Menu Screen

Second Menu Screen

Menu Commands

Default Conditions Upon Turn-On

Units of Measure

Available Units of Measure

Changing the Unit of Measure

Spatially Averaged Measurements

Understanding Spatial Averaging

Spatial Averaging with the 8718B

Data Logging

Logging Options

Logging Data

Format for Logged Data

Mode 1 Logging

Mode 2 Logging

Mode 3 Logging

Memory Capacity

Analog Output

Time-Averaged Measurements

Measurement Options

Making Time-Averaged Measurements

Mode 1 Averaging

Mode 2 Averaging

Alarm Settings

Alarm Description

Controlling the Alarm Functions

Fixed Alarm

Variable Tone Alarm

Using The RF Exposure Standards Feature

Application

Checking or Changing the Standard

Back Light and Battery Status

Application for Back Light