Microrad NHT-3D User Manual

NHT-3D

Complex signal analyzer

User Manual

Version 2.4 – May 2017

Design development and manufacturing

MICRORAD

Piazza delle Azalee 13/14
05019 Orvieto (TR) – ITALIA
Tel [phone]
Fax [phone]
email [e-mail]
web www.microrad.it

INDEX

1 GENERAL INFORMATION ................................................................................. 1

1.1 Application .......................................................................................................... 1

1.2 About the instrument ........................................................................................... 1

1.3 Operating modes ................................................................................................ 1

1.3.1 Frequency selective mode .......................................................................... 1

1.3.2 Wide band mode......................................................................................... 2

1.3.3 Single EMF measurement .......................................................................... 2

1.3.4 NHT-3D remote control using Waves software ........................................... 2

1.3.5 Downloading data to PC / Tablet ................................................................ 3

1.4 Measurement probes .......................................................................................... 3

1.4.1 Low frequency electric field probes............................................................. 3

1.4.2 Low frequency magnetic field probes ......................................................... 3

1.4.3 Magneto-static field probes ......................................................................... 3

1.4.4 Electromagnetic static and low frequency field probes ............................... 4

1.4.5 Radio-frequency electric field probes .......................................................... 4

1.4.6 Radio-frequency magnetic field probes ...................................................... 4

1.5 Exposure limits ................................................................................................... 4

1.5.1 Exposure limits for the population ............................................................... 5

1.5.2 Occupational exposure lower limits ............................................................ 5

1.5.3 Occupational exposure upper limits ............................................................ 6

1.5.4 Occupational exposure localized limits ....................................................... 6

1.6 Values and measurement indexes description ................................................... 7

1.6.1 Indexes displayed on the instrument .......................................................... 7

1.6.2 Indexes displayed through Waves software ............................................... 8

1.7 Filters .................................................................................................................. 9

1.7.1 1K span .................................................................................................... 10

1.7.2 20K span .................................................................................................. 10

1.7.3 400K span ................................................................................................ 10

1.7.4 50 Hz notch filter ....................................................................................... 10

1.7.5 50 Hz interference notch filter ................................................................... 11

1.7.6 DC filter ..................................................................................................... 11

1.8 Acoustic alarm .................................................................................................. 11

1.9 GPS module ..................................................................................................... 11

1.10 Temperature Sensor ......................................................................................... 12

1.11 Clock ................................................................................................................. 12

1.12 Equipment configuration ................................................................................... 12

1.13 NHT-3D Technical Specifications ..................................................................... 13

1.14 Normative references ....................................................................................... 14

1.15 Standard compliance ........................................................................................ 14

2 SAFETY INSTRUCTIONS ................................................................................ 15

2.1 Foreword ........................................................................................................... 15

2.2 Correct Use ....................................................................................................... 15

3 CERTIFICATION AND WARRANTY ................................................................ 16

3.1 Certification ....................................................................................................... 16

3.2 Warranty ........................................................................................................... 16

3.3 Limitation of warranty ........................................................................................ 16

4 UNIT DESCRIPTION ........................................................................................ 17

4.1 Front panel legend ............................................................................................ 17

4.2 Connectors and interfaces legend .................................................................... 20

5 PREPARATION FOR USE ............................................................................... 21

5.1 Unpacking ......................................................................................................... 21

5.2 Storage ............................................................................................................. 21

5.3 Connecting the probes ...................................................................................... 21

5.4 Power supply and autonomy ............................................................................. 22

6 OPERATION ..................................................................................................... 23

6.1 Base unit switching on ...................................................................................... 23

6.2 Main measuring screen .................................................................................... 25

6.3 Recording measured values ............................................................................. 28

6.3.1 Single storing ............................................................................................ 28

6.3.2 Monitoring ................................................................................................. 29

6.4 Measurement download and display ................................................................ 31

6.5 Alert levels ........................................................................................................ 31

6.6 Factory reset ..................................................................................................... 32

7 WAVES SOFTWARE ....................................................................................... 33

7.1 Introduction ....................................................................................................... 33

7.2 Software installation .......................................................................................... 33

7.3 Upper toolbar description .................................................................................. 34

7.4 Description of side panel controls ..................................................................... 37

7.5 Chart diagram operation ................................................................................... 39

7.5.1 Diagrams zoom and pan ........................................................................... 39

7.5.2 Diagrams pointers ..................................................................................... 39

7.5.3 Diagrams Markers .................................................................................... 40

7.6 Snapshot panel ................................................................................................. 41

7.7 Monitoring panel ............................................................................................... 42

7.7.1 Monitoring data numeric format ................................................................ 42

7.7.2 Monitoring data graphic format ................................................................. 44

7.8 GPS and Google maps ..................................................................................... 45

7.9 NHT-3D firmware update .................................................................................. 46

ANNEX A COMMUNICATION PROTOCOL .......................................................... 47

1

1 GENERAL INFORMATION

1.1 Application

Human exposure to electromagnetic fields (not ionizing radiation) is nowadays
a very critical subject almost all countries in the world are dealing with.
Technical and normative bodies work alongside government institutions to
enact new guidelines and decrees regarding maximum permitted exposure
levels for populations and workers.

The measurement equipment for this type of analysis must suit the technical
requirements from the guidelines and must provide the user with qualified
physical parameters for compliance with legally required thresholds.

1.2 About the instrument

The NHT-3D is the new Microrad solution for the measurement and analysis of
complex signals in the electromagnetic safety applications.

Besides being handy and compact, the instrument operates in selective mode
in the frequency band DC÷400 kHz, and in wide band mode up to 40 GHz.

It is user-friendly and provides extremely reliable measurements; it also
provides the operator with local temperature and GPS coordinates of the site
being measured for inclusion in a final report.

1.3 Operating modes

The instrument performs measurements in two different modes, depending on
the type of probe: selective frequency mode and wide band mode.

In both modes, acquisition and display of measurement data is continuous and
real time.

It is also possible to store individual measuring points (snapshots) or
continuous sequences (monitoring) that can then be downloaded to a PC /
Tablet and analyzed using Waves application.

Waves application software also allows the device to be remotely controlled
thus providing the operator with access to measured signal portions for in
depth analysis both in the time domain and in the frequency domain.

1.3.1 Frequency selective mode

In frequency selective mode, the signal is sampled very quickly, allowing its
exact reconstruction in the time domain, and a subsequent spectral analysis,
its comparison with normative masks, and calculation of weighted indexes
linked to frequency performance and exposure limits.

In this mode signals in the frequency band from DC to 400 kHz are measured.
The probes used in selective mode are the so-called low frequency probes
(probes for the electric field and the magnetic induction field) and probes for
the magneto-static field.

NHT-3D 1. General information

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1.3.2 Wide band mode

Wide band mode is typical of radio frequency probes for electric or magnetic
field, that are capable of measuring signals from approximately 100 kHz up to
40 GHz and over. These types of probes sample the signal after it has been
rectified within the probe. The probe provides the r.m.s. value (root mean
square), and it is no longer possible to discriminate the frequency information.
However, fast sampling allows to trace, with Waves application, a timeline of
the r.m.s. value, capable of representing impulsive signals with a width of few
microseconds.

1.3.3 Single EMF measurement

The main application of NHT-3D is to perform electromagnetic field
measurements allowing the user to make evaluations in relation to established
protective safeguards. The system uses a variety of probes to measure
specific physical parameters (magnetic induction, magnetic field and electric
field) according to the frequency band of interest.

On the instrument LCD display, are always displayed:

 Instantaneous isotropic value ISO of measured field.
 Instantaneous value on the three Cartesian axes X, Y, Z.
 Maximum value MAX of measured field.
 Moving average value r.m.s. in time domain AVG.
 Spatial average value SPT.
 Filter insertion status.
 Frequency Span on (

only in selective mode

).

 Regulation limit selected (

only in selective mode

).

 WP or Ib index (

only in selective mode

).

 Alarm threshold ALM.
 Measurement unit.
 GPS on/off.
 Temperature.
 Date and time clock.
 Battery charging level.

The instrument can be used in direct operating mode via the front keyboard
panel and the measurements can be viewed on the LCD display. The
instrument can also be remotely controlled by connecting it to a PC/Tablet via
fiber-optic, and using the Waves software.

1.3.4 NHT-3D remote control using Waves software

This operation mode is recommended in order to avoid where possible the
influence of the user's presence on the environment being measured (mainly
for electric field analysis) or when there is a requirement to install the
measurement system in a screened and controlled space (anechoic chamber

NHT-3D 1. General information

3

for EMC testing). In such a situation it is strongly recommended that a wooden
tripod with variable height (optional) is used.

NHT-3D can be remotely managed through a fiber optic connection to an
external PC/Tablet. The Waves software allows the total remote control of the
NHT-3D unit displaying measured values, indexes and masks relating to
occupational or population regulations. Simultaneously it displays the graphic
curves in the time domain and in the frequency domain, with high resolution
diagrams.

Additionally, Waves software can perform in-depth analysis of the signal,
computing additional evaluation indexes and allowing data and images to be
exported for post-analysis, reporting, and recording.

The display of the normative limits mask and the diagram in the frequency
domain is only possible in selective mode, using low frequency or magneto­static probes.

1.3.5 Downloading data to PC / Tablet

All measured values, recorded both as single acquisition or continuous
monitoring, can be downloaded to an external PC/Tablet through the fiber optic
cable using an optical/USB adapter.

Once the values have been transferred, they can be viewed and analyzed
within Waves software and saved on a hard disk or other mass storage units
for later reference. Data export in tabular format (Excel compatible) and
graphics, such as images, is also possible.

1.4 Measurement probes

Measurement probes available for use in conjunction with NHT-3D, are listed
below, according to the type of probe and field being measured:

1.4.1 Low frequency electric field probes

• 11E : for measurements of electric field (E) in the frequency range from
1Hz to 400kHz; measurement range from 20 V/m to 20 kV/m.

1.4.2 Low frequency magnetic field probes

• 10B : for measurements of magnetic induction (B) in the frequency
range from 1Hz to 400kHz; measurement range from 100 nT to 1 mT.

• 20B : for measurements of magnetic induction (B) in the frequency
range from 1Hz to 20kHz; measurement range from 300 nT to 16 mT.

• 30B : for measurements of magnetic induction (B) in the frequency
range from 1Hz to 400kHz; measurement range from 300 nT to 16 mT.

1.4.3 Magneto-static field probes

• 10H : for measurements of magnetic induction (B), static field only;
measurement range from 150 nT to 2.5 mT.

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• 20H : for measurements of magnetic induction (B) from static field up
to 1 kHz; measurement range from 1 mT to 15 T.

• 30H : for measurements of magnetic induction (B) from static field up
to 1 kHz; measurement range from 200uT to 600mT.

1.4.4 Electromagnetic static and low frequency field probes

• 33P : for measurements of electric field (33E) in the frequency range
from 1Hz to 400kHz, measurement range from 20 V/m to 20 kV/m, of
magnetic induction (33B) in the frequency range from 1Hz to 400kHz,
measurement range from 300 nT to 16 mT, and of magnetic induction
(33H), static field only, measurement range from 150 nT to 2.5 mT. The
3 measurements are combined in the same device, each of them can
be selected through a manual selector.

1.4.5 Radio-frequency electric field probes

• 01E : for measurements of electric field (E) in the frequency range
from 100 kHz to 6.5 GHz; measurement range from 0.2 V/m to 350
V/m.

• 02E : for measurements of electric field (E) in the frequency range
from 400 kHz to 40 MHz; measurement range from 2 V/m to 1’200
V/m.

• 03E : for measurements of electric field (E) in the frequency range
from 100 kHz to 18 GHz; measurement range from 0.8 V/m to 650
V/m.

• 04E : for measurements of electric field (E) in the frequency range
from 3 MHz to 40 GHz; measurement range from 0.5 V/m to 350 V/m.

1.4.6 Radio-frequency magnetic field probes

• 02H : for measurements of magnetic induction (B) in the frequency
range from 300 kHz to 30 MHz; measurement range from 0.016 A/m to
16 A/m.

Each probe is automatically recognized by the NHT-3D when inserted.
Please refer to our website for additional technical details on probes and for

availability of new products (www.microrad.it).

1.5 Exposure limits

The limit of the electric or magnetic field levels at a specific frequency value
represents the r.m.s. value of a sinusoidal field tone at that frequency, beyond
which health security is no longer guaranteed.

Different regulatory limits are implemented: population and working
environments. The latter, as defined by law [4], is generally subdivided into
lower, upper and localized levels, both for electric field and magnetic field;
localized levels are defined only for magnetic fields.

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The instrument performs an automatic analysis of compliance with exposure
limits only when it is working in selective frequency mode, even in the
presence of complex signals with bands up to 400 kHz, using low frequency
and magneto-static probes.

Exposure limits are in fact considered by the instrument in the calculation of
WP and Ib weighted indexes; these dimensionless indexes ensure that limits
are not exceeded when they have a value below 1.

Additionally, Waves software graphically represents the selected mask for the
limits within the signal diagram in the frequency domain, and uses them in the
calculation of the II98 and IRSS indexes.

1.5.1 Exposure limits for the population

For the population exposure mask, the reference levels contained in document
[1] paragraph 1.14 are adopted. The tables below show exposure limits for the
electric field and magnetic induction, up to 400 kHz.

Frequency E (V/m)

< 25 Hz 10’000

0.025 – 3 kHz 250/f
3 – 400 kHz 87

Tab. 1.1 – Electrical field limits for the population

Frequency B (uT)

< 1 Hz 40’000

1 – 8 Hz 40’000/f2

8 – 800 Hz 5’000/f

0.8 – 150 kHz 6.25

150 – 400 kHz 920/f

Tab. 1.2 – Magnetic field limits for the population

1.5.2 Occupational exposure lower limits

For the workplace mask, lower levels, the exposure limits are defined in
document [2] paragraph 1.14 and in document [4] Annex II paragraph B. The
tables below show the exposure limits for the electric field and magnetic
induction, up to 400 kHz.

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Frequency E (V/m)

< 25 Hz 20’000

0.025 – 3 kHz 500/f
3 – 400 kHz 170

Tab. 1.3 –

Electrical field limits for professional environments, lower levels

Frequency B (uT)

< 1 Hz 200’000

1 – 8 Hz 200’000/f2

8 – 25 Hz 25’000/f

25 – 300 Hz 1’000

0.3 – 3 kHz 300/f
3 – 400 kHz 100

Tab. 1.4 – Magnetic

field limits for professional environments, lower levels

1.5.3 Occupational exposure upper limits

For the workplace mask, upper levels, the exposure limits are defined in
document [4] Annex II paragraph B. The tables below show the exposure limits
for the electric field and magnetic induction, up to 400 kHz.

Frequency E (V/m)

< 50 Hz 20’000

0.050 – 1.64 kHz 1000/f

1.64 – 400 kHz 610

Tab. 1.5 –

Electrical field limits for professional environments, upper levels

Frequency B (uT)

< 1 Hz 300’000

0.001 – 3 kHz 300/f
3 – 400 kHz 100

Tab. 1.6 –

Magnetic field limits for professional environments, upper levels

1.5.4 Occupational exposure localized limits

For the workplace mask, localized levels, the exposure limits are defined in
document [4] Annex II paragraph B. The tables below show the exposure limits
for the magnetic induction, up to 400 kHz. Localized levels are not defined for
the electric field.

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Frequency B (uT)

< 1 Hz 900’000

0.001 – 3 kHz 900/f
3 – 400 kHz 300

Tab. 1.7 –

Magnetic field limits for professional environments, localized levels

1.6 Values and measurement indexes description

1.6.1 Indexes displayed on the instrument

The NHT-3D device calculates and displays on its screen the following values
and measurement indexes:



 ISO: instantaneous isotropic value of the field, and corresponds to the

value displayed in large digits on the instrument screen; even if it is
called instantaneous, in reality it is an r.m.s. average value. The
average is calculated on a moving window. The time window width
depends on the selected span: with 400K span the window is 8.2 ms,
with 20K span it’s 163.8 ms, with1K span it’s 3.3 s. For wide-band
probes, where the span cannot be selected, the window is 163.8 ms.

 MAX: is equal to the maximum ISO value; it displays the maximum

value measured from insertion of the probe or from last reset. This
value is updated only when a new higher amplitude value is reached. A
reset from the keyboard can be performed when required.

 X, Y, Z: are the 3 Cartesian components of ISO value.



 AVG: long-term r.m.s. value; the average is calculated on a moving

window. The time window width is configurable via Waves application
from a minimum of 1 s up to a maximum of 192 minutes; a reset from
the keyboard can be performed. The AVG value is evaluated only after
a period of time equal to the length of the moving window has been
completed (starting from power on, from insertion of the probe or from
the average reset).

 SPT: represents the r.m.s. value of points acquired through single

acquisitions. This function can be useful to quickly obtain an average
value in space when capturing two or more values in different locations
from which spatial average name is derived. A reset from the keyboard
can be performed if/ when required. The SPT value is also reset when
the instrument is switched on or when the probe is changed.

 WP: weighted peak index, is implemented according to the indications

in document [2] appendix. The weighted peak index allows the operator,
even in the presence of complex signals, to quickly evaluate whether
regulatory limits have been exceeded; in fact, the index is a
dimensionless number, and ensures that exposure limits are not

NHT-3D 1. General information

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exceeded when its value is less than 1. It is calculated from the
instrument using a weighted digital filter, whose parameters vary
according to the type of probe (electrical or magnetic) and to selected
exposure limits (population, lower higher, and localized occupational)
for a total of 7 different configurations (localized is defined only for
magnetic probes). The WP index is equal to the output peak value of
the digital weighted filter. The index is available only in selective mode,
for low frequency or magneto-static probes, since it is defined only for
signals with a bandwidth between 1 Hz and 100 kHz. Span selections or
notch filters activation do not affect the calculation and result of the
index.

 Ib: weighted index implemented as defined in [3] "time domain

evaluation" section, with characteristics similar to those of the weighted
peak. The main difference is in the definition band, that is extended up
to 400 kHz, and in the index that is not equal to the peak but it’s the
r.m.s. value of the signal at the weighted digital filter output. The Ib
index is available only in frequency selective operation mode, and the
span selections or the activation of notch filters will not affect the
processing.

1.6.2 Indexes displayed through Waves software

The Waves software can display all individual samples (real instantaneous
values, non-mediated) in a diagram in the time domain; furthermore, if the
instrument is in selective mode, the application, when performing the FFT
operation, is also able to represent in detail the information regarding to the
frequency domain of the acquired signal.

All this enables the processing and display on PC / Tablet of the following
values / measurement indexes:

 RMS: r.m.s. isotropic value of samples acquired within the window and

represented in the time diagram, consisting of 65'536 instantaneous
consecutive field values.

 Peak: the maximum isotropic value of the samples acquired within the

window and represented in the time diagram.

 WP and Ib: are the weighted indexes calculated by the instrument and

transferred to the application that returns them to screen without any
additional processing. They do not depend on the selected span.

 II98: Index calculated according to the following formula [1]:

II98 =

ΣΣΣΣ

j

(

( (

(

F

j

/

L

j

))))

F

j

= field component (r.m.s. value) at frequency j;

L

j

= exposure limit at frequency j;

j = frequency included in the range from 1 Hz to the upper limit for the

selected span (1, 20 or 400 kHz).

NHT-3D 1. General information

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II98 value is therefore influenced by the selected span, since it defines
the upper limit where the summation stops. The index is a non­dimensional number and it ensures that limits are not exceeded when
its value is less than 1. II98 index is available only in frequency
selective mode.

 IRSS: index calculated according to the following formula:

IRSS =

√

Σ

j

(

F

j

/

L

j

)2

F

j

= field component (r.m.s. value) at frequency j;

L

j

= exposure limit at frequency j;

j = frequency included in the range from 1 Hz to the upper limit for the

selected span (1, 20 or 400 kHz).

IRSS value is therefore influenced by the selected span, since it define
the upper limit where the summation stops. The index is a non­dimensional number and it ensures that limits are not exceeded when
its value is less than 1. IRSS index is available only in frequency
selective mode.

 Fmax: represents the frequency, within the selected span, where the

spectral component of the signal has the highest intensity. This indicator
is available only in selective frequency mode.

 Irms: index calculated according to the following formula:

Irms = RMS

/

L

Fmax

RMS

= wide band field r.m.s. value;

L

Fmax

= exposure limit at the frequency Fmax of greatest contribution.

In practice, this index is calculated assuming all the power of the signal
is concentrated at Fmax frequency. The index is a non-dimensional
number and it ensures that limits are not exceeded when its value is
less than 1. IRMS index is available only in frequency selective mode.

1.7 Filters

The NHT-3D instrument is internally equipped with selectable digital filters,
that can facilitate measurement by cutting off negligible bandwidths or
selecting the frequencies that originate the captured signal.

The available filters are those related to the frequency span selection (1K, 20K
400K) and those for the suppression / rejection of the 50Hz or DC components
of the signal.

The filters can be activated via keyboard or remotely, and for each probe,
according to the type, it is possible to enable a specific set of filters.

NHT-3D 1. General information

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1.7.1 1K span

The 1K span is selectable for all types of low frequency probe or for magneto­static probes.

The filter function is to cut all spectral components above 1 kHz, leaving
undisturbed those up to 1 kHz (low pass filter). Specifically, above 2.5 kHz an
attenuation of more than 100 dB is achieved.

When 1K span is selected, the instrument works at a sampling rate of 5 Ksps,
corresponding to an interval of 200 us between one sample and the next.

1.7.2 20K span

The 20K span is selectable for all types of probes excluding magneto-static.
Also radiofrequency probes typically use the 20K span.

The filter function is to cut all spectral components above 20 kHz, leaving
undisturbed those up to 20 kHz (low pass filter). Specifically, above 50 kHz an
attenuation of more than 100 dB is achieved.

When 20K span is selected, the instrument works at a sampling rate of 100
Ksps, corresponding to an interval of 10 us between one sample and the next.

Note that in order to maximize rejection due to out-of-band disturbances, this
filter remains inserted even when working with the 1K span.

1.7.3 400K span

The 400K span is selectable for all types of low frequency probes capable of
working at over 20 kHz.

The function of this filter is to cut all spectral components above 400 kHz,
leaving undisturbed those up to 400 kHz (low pass filter). Specifically, above
500 kHz an attenuation of more than 100 dB is achieved.

When 400K span is selected, the instrument works at a sampling rate of 2
Msps, corresponding to an interval of 500 ns between one sample and the
next.

Note that in order to maximize rejection due to out-of-band disturbances, this
filter remains inserted even when working with 20K and 1K span.

1.7.4 50 Hz notch filter

The 50 Hz notch filter is available for low frequency probes, electrical and
magnetic (not for magneto-static probes).

The function of this filter is to suppress the spectral components generated
from the 50Hz mains supply. The filter is characterized by a 50Hz component
attenuation greater than 40 dB, and a stop bandwidth (-3dB) smaller than 0.5
Hz.

The filter can be activated only when the 1 kHz frequency span is selected.

NHT-3D 1. General information

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1.7.5 50 Hz interference notch filter

The 50 Hz interference notch filter is defined only for radiofrequency probes.
The filter suppresses the 50 Hz disturbances induced by high electrical fields,

such proximity to electricity grid or to powered devices.
In fact, although the radiofrequency probes have an intrinsic rejection of the 50

Hz field, since typically the sensitivity band starts from tens or hundreds of
kHz, the presence of very strong components may disturb the measurement
results.

The filter introduces an attenuation of the 50 Hz component greater than 50
dB and a stop bandwidth (-3dB) smaller than 8 Hz.

1.7.6 DC filter

The DC component filter is used only with magneto-static probes (except 10H,
33H probes), since they are the only ones capable of measuring the
continuous components of the field.

It is a high-pass filter of the first order that completely eliminates the
continuous component of the signal and leaves all the AC components.

The -3dB cut-off frequency is less than 0.1 Hz.

1.8 Acoustic alarm

The instrument is equipped with an acoustic alarm that, when activated,
alerts the operator when an isotropic value being measured has exceeded a
predefined field threshold.

The alarm can be switched on and off using the instrument keyboard, while the
thresholds are configurable using the Waves software.

In particular, three different thresholds can be set: a threshold is used in
conjunction with low frequency electric probes, another with low frequency or
magneto-static magnetic probes, the last with radio frequency probes.

1.9 GPS module

NHT-3D integrates a GPS module to acquire geographic coordinates as
reference to the area in which the measurements were carried out.

In case of outdoor activities, it is always recommended to add the GPS data
related to the measurement site in order to mention them in the final report.
GPS associates not only geographic information but also the exact time (UTC
time).

No other external device is required to perform these operations as the NHT­3D performs the measurement and automatically provides field values
together with GPS coordinates of the site. The Waves software can directly
show it on Google Maps™.

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1.10 Temperature Sensor

In addition NHT-3D integrates a temperature sensor acquiring the
temperature value during measurement activity.

Since the sensor is integrated into the front of the instrument, it is necessary to
consider that, as the meter shell is a good thermal conductor, the
measurement may be influenced by the operator's hand temperature. In order
to have exact temperature values, the instrument must be used with a tripod
support.

1.11 Clock

NHT-3D integrates a RTC (Real Time Clock) device that can perform clock
and calendar functions. The date and time can be synchronized to those of the
PC through the Waves software.

The RTC device is equipped with a battery to keep the time information even
when the instrument is switched off. The battery life is limited to a number of
years. When the battery is exhausted or low the following message is
displayed : "RTC ERROR" during the instrument power-on phase at which
point the date and time are no longer stored in memory.

Replacement of the internal battery can only be performed by qualified
personnel, sending the instrument to the mother company for maintenance.

1.12 Equipment configuration

The basic unit NHT-3D is delivered in the standard configuration including:

 NHT-3D basic unit for measuring, storing and display field data
 Fiber optic cable (10 meters length)
 Fiber-USB adapter to link fiber optic to PC
 USB A/B adapter cable
 Battery charger
 Waves software and user manual (available on website www.microrad.it)
 ISO 9001:2008 calibration certificates

In order to proper work the NHT-3D meter must be connected to a
measurement probe to be chosen among the available ones.

: