I-Tech IT9121 Series User manual

Power meter
IT9121 Series User Manual
Model: IT9121
Version:V1.4

IT9121 User Manual
Notices
© ItechElectronic, Co., Ltd. 2017
No part of this manual may be
reproduced in any form or by any means
(including electronic storage and
retrieval or translation into a foreign
language) without prior permission and
written consent from Itech Electronic,
Co., Ltd. as governed by international
copyright laws.
Manual Part Number
IT9121-402145
Revision
1st Edition: June 27, 2017
Itech Electronic, Co., Ltd.
Trademarks
Pentium is U.S. registered trademarks
of Intel Corporation.
Microsoft, Visual Studio, Windows and
MS Windows are registered trademarks
of Microsoft Corporation in the United
States and/or other countries and
regions.
Warranty
The materials contained in this
document are provided “as is”, and
is subject to change, without prior
notice, in future editions. Further, to
the maximum extent permitted by
applicable laws, ITECH disclaims
all warrants, either express or
implied, with regard to this manual
and any information contained
herein, including but not limited to
the implied warranties of
merchantability and fitness for a
particular purpose. ITECH shall not
be held liable for errors or for
incidental or indirect damages in
connection with the furnishing, use
or application of this document or of
any information contained herein.
Should ITECh and the user enter
into a separate written agreement
with warranty terms covering the
materials in this document that
conflict with these terms, the
warranty terms in the separate
agreement shall prevail.
Technology Licenses
The hardware and/or software
described herein are furnished under a
license and may be used or copied only
in accordance with the terms of such
license.
Restricted Rights Legend
U.S. Government Restricted Rights.
Software and technical data rights
granted to the federal government
include only those rights customarily
provided to end user customers. ITECH
provides this customary commercial
license in software and technical
data pursuant to FAR 12.211
(Technical Data) and 12.212
(Computer Software) and, for the
Department of Defense, DFARS
252.227-7015 (Technical Data –
Commercial Items) and DFARS
227.7202-3 (Rights in Commercial
Computer Software or Computer
Software Documentation).
Safety Notices
A CAUTION sign denotes a
hazard. It calls attention to an
operating procedure or practice
that, if not correctly performed
or adhered to, could result in
damage to the product or loss of
important data. Do not proceed
beyond a CAUTION sign until
the indicated conditions are fully
understood and met.
A WARNING sign denotes a
hazard. It calls attention to an
operating procedure or practice
that, if not correctly performed
or adhered to, could result in
personal injury or death. Do
not proceed beyond a
WARNING sign until the
indicated conditions are fully
understood and met.
NOTE
A NOTE sign denotes important
hint. It calls attention to tips or
supplementary information that
is essential for users to refer to.
.

IT9121 User Manual
Copyright © Itech Electronics Co., Ltd. i
Quality Certification and Assurance
We certify that T9121 power meter meets all the published specifications.
Warranty ITECH warrants that the product will be free from defects in material and
workmanship under normal use for a period of one (1) year from the date of
delivery (except those described in the Limitation of Warranty below).
For warranty service or repair, the product must be returned to a service center
designated by ITECH.
The product returned to ITECH for warranty service must be shipped PREPAID.
And ITECH will pay for return of the product to customer.
If the product is returned to ITECH for warranty service from overseas, all the
freights, duties and other taxes shall be on the account of customer.
Limitation of Warranty
This Warranty will be rendered invalid if the product is:
Damaged resulting from customer-wired circuits or customer-supplied parts or
accessories;
Modified or repaired by customer without authorization;
Damaged resulting from customer-wired circuits or use in an environment not
designated by us;
The product model or serial number is altered, deleted, removed or made
illegible by customer;
Damaged as a result of accidents, including but not limited to lightning,
moisture, fire, improper use or negligence.
Safety Symbols
Direct current
ON (power)
Alternating current
OFF (power)
Both direct and alternating
current
Power-on state
Protective earth (ground)
terminal
Power-off state
Earth (ground) terminal
Reference terminal
Caution
Positive terminal
Warning (refer to this manual
for specific Warning or
Caution information)
Negative terminal
A chassis terminal
-
-

IT9121 User’s Manual
Copyright © Itech Electronics Co., Ltd. ii
Safety Precautions
The following safety precautions must be observed during all phases of
operation of this instrument. Failure to comply with these precautions or specific
warnings elsewhere in this manual will constitute a default under safety
standards of design, manufacture and intended use of the instrument. ITECH
assumes no liability for the customer’s failure to comply with these precautions.
Do not use the instrument if it is damaged. Before operation, check the
casing to see whether it cracks or is not applied with sufficient plastics. Do
not operate the instrument in the presence of inflammable gasses, vapors
or dusts.
The maximum operating voltage and current of the instrument are 600V
and 20Arespectively. Exceeding these limits will lead to burnout of the
instrument.
Make sure to use the power cord supplied by ITECH.
Check all marks on the instrument before connecting the instrument to
power supply.
Turn off the instrument and the operation system before connecting to the
I/O terminal.
Do not use the instrument if the detachable cover is removed or loosen.
Do not connect the instrument to any cable or terminal block before
self-testing.
To prevent the possibility of accidental injuries, be sure to use the power
adapter supplied by the manufacturer only.
We do not accept responsibility for any direct or indirect financial damage
or loss of profit that might occur when using the instrument.
This instrument is used for industrial purposes. Do not apply this product to
IT power supply system.
Never use the instrument with a life-support system or any other equipment
subject to safety requirements.
Failure to use the instrument as directed by the manufacturer may render
its protective features void.
Always clean the casing with a dry cloth. Do not clean the internals.
Make sure the vent hole is always unblocked.
Environmental Conditions
The instrument is designed for indoor use and an area with low condensation.
The table below shows the general environmental requirements for the
instrument.
Environmental Conditions
Requirements
Operating temperature
5°C-40°C
Operating humidity
humidity 20%-80%
(non-condensation)
Storage temperature
-20°C-50 °C
Altitude
Operating up to 2,000 meters

IT9121 User’s Manual
Copyright © Itech Electronics Co., Ltd. iii
Installation category
II
Pollution degree
Pollution degree 2
NOTE
To make accurate measurements, allow the instrument to warm up for 30 min.
Regulatory Markings
The CE mark indicates that the product
complies with all the relevant European
legal
directives. The specific year (if any)
affixed refers to the year when the design
was approved.
The instrument complies with the WEEE
Directive (2002/96/EC) marking
requirement. This affix product label
indicates that you must not discard the
electrical
/electronic product in domestic
household waste.
This symbol indicates the time period
during which no hazardous or toxic
substances are expected to leak or
deteriorate during normal use. The
expected useful life of the product is 10
years. The product
can be used safely
during the 10-
year Environment Friendly
Use Period (EFUP). Upon expiration of
the EFUP, the product must be
immediately recycled.
Waste Electrical and Electronic Equiment (WEEE)
Directive
2002/96/EC Waste Electrical and Electronic Equipment
(WEEE) Directive
This product complies with the WEEE Directive (2002/96/EC)
marking requirement. This affix product label indicates that you
must not discard the electrical/electronic product in domestic
household waste.
Product Category
With
reference to the equipment classifications described in the
Annex 1 of the WEEE Directive, this instrument is classified as
a “Monitoring and Control Instrument”.
To return this unwanted instrument, contact your nearest ITECH
office.

IT9121 User’s Manual
Copyright © Itech Electronics Co., Ltd. iv
Compliance Information
Complies with the essential requirements of the following applicable European
Directives, and carries the CE marking accordingly:
Electromagnetic Compatibility (EMC) Directive 2014/30/EU
Low-Voltage Directive (Safety) 2014/35/EU
Conforms with the following product standards:
EMC Standard
IEC 61326-1:2012/ EN 61326-1:2013 ¹²³
Reference Standards
CISPR 11:2009+A1:2010/ EN 55011:2009+A1:2010 (Group 1, Class A)
IEC 61000-4-2:2008/ EN 61000-4-2:2009
IEC 61000-4-3:2006+A1:2007+A2:2010/ EN 61000-4-3:2006+A1:2008+A2:2010
IEC 61000-4-4:2004+A1:2010/ EN 61000-4-4:2004+A1:2010
IEC 61000-4-5:2005/ EN 61000-4-5:2006
IEC 61000-4-6:2008/ EN 61000-4-6:2009
IEC 61000-4-11:2004/ EN 61000-4-11:2004
1. The product is intended for use in non-residential/non-domestic environments. Use of the
product in residential/domestic environments may cause electromagnetic interference.
2. Connection of the instrument to a test object may produce radiations beyond the specified
limit.
3. Use high-performance shielded interface cable to ensure conformity with the EMC standards
listed above.
Safety Standard
IEC 61010-1:2010/ EN 61010-1:2010

IT9121 User’s Manual
Copyright © Itech Electronics Co., Ltd. v
Content
Quality Certification and Assurance....................................................................................................................... 1
Warranty............................................................................................................................................................... 1
Limitation of Warranty .......................................................................................................................................... 1
Safety Symbols ...................................................................................................................................................... 1
Safety Precautions................................................................................................................................................. 2
Environmental Conditions ..................................................................................................................................... 2
Regulatory Markings ............................................................................................................................................. 3
Waste Electrical and Electronic Equiment (WEEE) Directive ................................................................................... 3
Compliance Information........................................................................................................................................ 4
Chapter1 Introduction ..................................................................................................................................... 1
1.1 Brief Introduction ............................................................................................................................................ 1
1.2 Introduction of front panels............................................................................................................................. 2
1.3 Introduction to keyboard................................................................................................................................. 2
1.4 Introduction of Menu Function........................................................................................................................ 3
1.5 Introduction of Interface Display Information .................................................................................................. 5
1.6 Introduction of Interface Symbols.................................................................................................................... 5
1.7 Introduction of rear panels .............................................................................................................................. 6
Chapter2 Measurement Conditions................................................................................................................. 7
2.1 Setting of Measurement Range ....................................................................................................................... 7
2.2 Setting of Measurement Interval ..................................................................................................................... 9
2.3 Setting of Filter and Crest Factor.................................................................................................................... 11
2.4 Setting of Averaging Function ........................................................................................................................ 12
Chapter3 Basic Measurement Functions ....................................................................................................... 15
3.1 Basic Concepts .............................................................................................................................................. 15
3.2 Setting of Measurement Function and Interface Display................................................................................ 16
Chapter4 Waveform Display Function ........................................................................................................... 18
4.1 Basic Concepts .............................................................................................................................................. 18
4.2 Adjustment of Measurement Parameters ...................................................................................................... 21
4.3 Setting of Trigger Configuration ..................................................................................................................... 21
Chapter5 Integral Operation Function ........................................................................................................... 23
5.1 Basic Concepts .............................................................................................................................................. 23
5.2 Setting of Integral Measurement Configuration ............................................................................................. 27
5.3 Integration..................................................................................................................................................... 29
Chapter6 Harmonic Measurement Function.................................................................................................. 32
6.1 Basic Concepts .............................................................................................................................................. 32
6.2 Setting of Harmonic Measurement Configuration.......................................................................................... 35
Chapter7 Routine Maintenance ..................................................................................................................... 38
7.1 Self-inspection............................................................................................................................................... 38
7.2 Error Information References ........................................................................................................................ 38
7.3 Daily maintenance......................................................................................................................................... 40
7.4 Contact of ITECH Engineers............................................................................................................................ 40
Chapter8 Technical Specifications.................................................................................................................. 42
8.1 General Specification..................................................................................................................................... 42
8.2 Screen Display ............................................................................................................................................... 42
8.3 Input Parameters........................................................................................................................................... 42
8.4 Voltage and Current Accuracy........................................................................................................................ 44
8.5 Active Power Accuracy .................................................................................................................................. 44
8.6 Voltage Current and Power measurements.................................................................................................... 45
8.7 Frequency Measurement............................................................................................................................... 47
8.8 Harmonic Measurement................................................................................................................................ 47

IT9121 User’s Manual
Copyright © Itech Electronics Co., Ltd. vi
8.9 Fundamental Frequency ................................................................................................................................ 48
8.10 Accuracy...................................................................................................................................................... 48
8.11 Oscilloscope Function .................................................................................................................................. 49
8.12 Interface Specification ................................................................................................................................. 49

Introduction
Copyright © Itech Electronics Co., Ltd. 1
Chapter1 Introduction
1.1 Brief Introduction
The IT9121 power meter can provide the maximum input of 600Vrms and
20Arms and the measurement bandwidth of 100KHZ and thus can be easily
used for measuring the parametersincluding voltage, current, power, frequency
and harmonics. Standard configuration includes USB, GPIB, RS232 and LAN
communication interfaces and also the interface for USB peripherals. The user
can store the measured parameters in the external storage medium. The
voltage and current precision is 0.1%. The instrument also has many integral
functions, such as the active power. The product can be widely applied in
motors, household appliances, UPS and other test fields.
Features
4.3-inch color liquid crystal display (TFT)
The number of matrix columns to be displayed on the screen and the
commonly used measurement parameters can be set freely.
Input range:600Vrms/20Arms
The voltage, current, power, harmonics and other parameters can be
measured at the same time.
The precision of voltage and current measurement is up to 0.1%.
It has the harmonic measuring function and can measure 50-order
harmonic components at most.
With the interface for USB peripherals, the user can store the interface in
the external storage medium.
With many powerful integral functions, the bought/sold electricity can be
calculated.
Frequency measurement function
Built-in USB, GPIB, RS232 and LAN communication interfaces
Application advantages
Analysis of UPS power quality:
As an important backup power supply in the communication industry, the
steady-state characteristics, dynamic characteristics, power quality and
other parameters of UPS should be analyzed. With internal nonlinear
elements, the UPS power supply will generate a large number of harmonic
components during operation, which may affect operation of the
communication system. The IT9121 power meter can measure such
parameters as the AC/DC signal, power factor, harmonics, frequency and
distortion factor, and systematically and comprehensively analyze the
performance of the UPS power supply.
Test of performance of household appliances:
With promotion of the concept of using energy in a rational and
environmentally friendly manner, more and more household appliances
adopt the variable frequency control technology to reduce the power
consumption. The IT9121 power meter can measure the inrush current,
active power, crest factor, etc.

Introduction
Copyright © Itech Electronics Co., Ltd. 2
1.2 Introduction of front panels
Schematic Diagram of Front Panel of IT9121 Series Power Meter and Diagram
of Key Functions.
1 USB Interface
2. Display
3. Menu key
4. Waveform Display key
5 Basic functions
6. Harmonic key
7. Integrator key
8. Setting knob
9. Arrow keys
10. Hold/Esc key
11. Enter key
12. Image Save key
13 Parameter setting key
14. Menu key
15 Power switch
1.3 Introduction to keyboard
The functions of keys on the front panel of the IT9121 series power meter are
shown in the following table.
Key tag
Name and function
Waveform Display key When this key is pressed,the waveform
corresponding to current measurement data will be displayed.
Harmonic Measurement key When this key is pressed, the
harmonic measurement results and the menu of harmonic
measurement parameter configuration will be displayed.
Basic Measurement key When this key is pressed, the
measurement data of various items will be displayed.
Integral Measurement key When this key is pressed, the integral
measurement results and the menu of integral measurement
parameter configuration will be displayed.
Menu key, used for setting relevant measurement parameters of
the power meter.
Enter key, used for saving the settings.
Image Save key
Cancel/ESC key
The front panel keyboard can be locked/unlocked when the ESC
key is constantly pressed for 5s.
The remote control mode of the power meter can be switched to
the panel operation mode when
the ESC key is constantly
pressed for 5s.

Introduction
Copyright © Itech Electronics Co., Ltd. 3
Key tag
Name and function
Up/Down key and Left/Right key
List Edit: those lines which are not displayed can be displayed by
operating the Left/Right key. Those rows which are not displayed
can be displayed by operating the Up/Down key.
Menu Edit: the programming items can be rolled by operating
the Up/Down key. Prompts of corresponding options are
displayed on the right and options can be selected via the soft
key.
Digit Edit: the programming items can be rolled by operating the
Up/
Down key. The digit to be edited is selected by operating the
Left/Right key or via the knob. Carrying can be completed
automatically.
Soft key The contents on the left of the key and the menu
function displayed above the key on the display screen may be
subject to changes.
Knob key, used for setting the value indicated by the cursor,
selecting the voltage and current range, adjusting the waveform,
etc.
1.4 Introduction of Menu Function
Press this key to enter the system menu function. Menu is described as
follows.
Menu Menu setting
SYSTEM
SYSTEM INFO
Instrument system
information
Model Instrument model
Serial
Instrument SN
Cpu Version
The version of CPU
Dsp Version
The version of Digital Signal Processing
MAC address
Network hardware address
Socket Port
Port number
COMM CONFIG Communication
configuration
R232
BAUD Rate
Set the communication baud
rate:4800/9600/19200/38400/57600/115200
Parity Chack
Communication parity check bit: Default:
NONE
Data bit
Communication data bit: 8 (default)
Stop bit
Communication stop bit: 1 (default)
USB Type B Connect
Select the USB communication interface.
GPIB GPIB Address
The address is adjustable between 1 and 30.
LAN
IP mode
IP mode: MANU/DHCP
IPAddress
IP address setting
Subnet mask
Set the subnetmask.
Gateway
Set the gateway.

Introduction
Copyright © Itech Electronics Co., Ltd. 4
SYSTEM CONFIG
System configuration
Date (YY/MM/DD)
System date: Year/Month/Day
Time (hh:mm:ss)
System time: Hour/Minute/Second
Brightness
Set the screen brightness.
Beep
Set the keyboard sound
SELF TEST
Self test
SYSTEM SELF_TEST
Self test
INITIAL
Initialize
SYSTEM INITIAL
System initialization
SETUP
SETUP INFO
Configuration information
Averag
Average
Sync Source
Synchronization
Line Filter
Line filter
Update Rate
Data updating rate
Freq Filter
Frequency filter
Crest Factor
Crest factor
ExSensor1
External current sensor 1 (range:
CF=3:2.5V,5V,10V; CF=6:1.25V, 2.5V,5V.)
ExSensor2
External current sensor 2 (range:
CF=3:50mV,100mV,200mV,500mV,1V,2V;
CF=6:25 mV,50mV,100mV,250mV,0.5V,1V.)
Rate(V/A)
Conversion ratio of external current sensor 1
Rate(mV/A)
Conversion ratio of external current sensor 2
U_Range
Voltage range
I_Range
Current range
AVERAG SET
Average function setting
State
Status
Mode
Mode
Type
Loading Type
Count
Counting cycle
EXT SEN SET
External current sensor
setting
EXSENSOR 1
Set the external current sensor 1: ON/OFF
Ratio(V/A)
Set the conversion ratio of the external
current sensor 1
EXSENSOR 2
Set the external current sensor 2: ON/OFF
Ratio(mV/A)
Set the conversion ratio of the external
current sensor 2
OTHER SET
Other settings
Sync Source
Select the synchronization source: U/I/OFF
Freq Filter
Set the frequency filter: ON/OFF
Line Filter
Set theline filter: ON/OFF
Crest Factor
Set the crest factor: CF3/CF6
Update Rate
Set the data updating rate:
0.1s/0.25s/0.5s/1s/2s/5s
INRUSH SET
Inrush setting

Introduction
Copyright © Itech Electronics Co., Ltd. 5
State
Status
Trig level(A)
Trigger level
Delay time(ms)
Delay time
Measure time(s)
Measuring time
CAL ZERO Calibration Zero
Zero point calibration
Calibration Zero
Zero point calibration
1.5 Introduction of Interface Display Information
The IT9121 power meter has four measurement modes. Below is the
introduction of basic interface information, with the basic measurement
interface as an example.
Basic measurement interface
Select the “Meter” button, and the initial interface of basic measurement as
shown below will appear.
1.6 Introduction of Interface Symbols
The interface of the IT9121 power meter will display the following symbols.
Status Bar icon
Status description
This icon appears when the line filter is
switched on.
This icon appears when the frequency filter is
switched on.
This icon appears when USB is inserted.
Over-voltage protection icon: this icon appears
when over-voltage occurs.
Over-current protection icon: this icon appears
when over-current occurs.

Introduction
Copyright © Itech Electronics Co., Ltd. 6
Status Bar icon
Status description
Key Lock: this icon appears when the keyboard
is locked.
Remote Lock: this icon appears in remote
operation and then local keys fail.
This icon appears in remote network
connection.
1.7 Introduction of rear panels
Schematic Diagram of Rear Panel of IT9121 Power Meter.
1. GPIB interface
2 Ethernet interface
3 USB Interface
4. RS232 interface
5. External synchronization signal interface
6 Power interface
7. External sensor interface
8. Voltage input terminal
9. Current input terminal
Warning: The external sensor interface (as shown in Fig. 7 above) of IT
9121 power meter is installed with a protective jacket at ex-factory, which
should be correctly installed at all circumstances unless an external sensor
permitted by ITECH is used.

Measurement Conditions
Copyright © Itech Electronics Co., Ltd. 7
Chapter2 Measurement Conditions
This chapter describes details of relevant work to be finished before use of the
IT9121 power meter.
2.1 Setting of Measurement Range
The appropriate measurement range (voltage and current range) must be set
for accurate measurement. The selected range is effective for different
measurement modes, such as waveform display, integral measurement and
harmonic measurement.
Operation steps
1. In the “Meter” interface Press the soft key corresponding to “V-RANGE” or
“A-RANGE”, and use the knob or “ ” to select the voltage or current
range.
2. Press the “Enter” key to confirm the setting. The instrument will
automatically confirm and exit the setting in case of no operation on the
interface for more than 5s.
When the crest factor is 6:
Figure: Voltage Range
Figure: Current Range

Measurement Conditions
Copyright © Itech Electronics Co., Ltd. 8
When the crest factor is 3:
Figure: Voltage Range
Figure: Current Range
NOTE
When EX1 or EX2 is installed, the power meter has more current range options. See details
in IT9121 Installation Instructions.
Voltage and current range
Set the measurement range according to the level of the effective value. When
the voltage or current signal is input into the input unit, there are two types of
range: fixed and automatic.
Fixed range Select the required range from a number of options. After selection, the range
will not change with the input signal. For the voltage range, when the crest
factor is 3, the maximum option is “600V” and the minimum option is “15V”.
When the crest factor is 6, the maximum option is “300V” and the minimum
option is “7.5V”.

Measurement Conditions
Copyright © Itech Electronics Co., Ltd. 9
NOTE
During measurement of the distortion waveform and other non-sinusoidal wave signals, the
accuracy of measurement can be improved by selecting the minimum range on the premise
that the measured value does not exceed the range.
Auto-measuring span
The range is switched automatically according to the input signal. The range
types for switching are the same as those of the fixed range.
Principles of automatic range level increase:
The range level is increased when any one of the following conditions is
satisfied.
Urms or Irms exceeds 110% of the current range setting.
The crest factor is 3. The value Upk or Ipkof the input signal exceeds 330%
of the current range setting.
The crest factor is 6. The value Upk or Ipk of the input signal exceeds 660 %
of the current range setting.
Principles of automatic range level decrease:
The range level is decreased when all of the following conditions are satisfied.
Urms or Irms is less than or equal to 30% of the current measurement
range.
The crest factor is 3. The value Upk or Ipk of the input signal is less than
300% of the range at the following level.
The crest factor is 6. The value Upk or Ipk of the input signal is less than
600 % of the range at the following level.
NOTE
The selected automatic range may change when the input waveform is a pulse waveform of uncertain
cycle. In this case, the fixed range should be selected.
2.2 Setting of Measurement Interval
The time for acquisition of sampling data is determined by the measurement
interval during measurement. The measurement interval is determined by the
data updating rate and synchronization source. The synchronization source
provides reference signals for measurement, and the data updating rate
determines the updating cycle of sampling data.
Measurement interval
The measurement interval is determined by the data updating rate and
synchronization source. (see “2.3 Setting of Filter and Crest Factor” for specific
settings)
Synchronization
IT9121 adopts the frequency measurement circuit to test the input signal cycle
set in the measurement interval. The measurement interval is the integer times
of the test cycle. The measured value of IT9121 is calculated by averaging
sampling data in the measurement interval. The reference input signal used for
defining the input signal measurement interval is called the synchronization
source.
Measurement interval for conventional measurement
The measurement interval of the reference input signal is the time from the

Measurement Conditions
Copyright © Itech Electronics Co., Ltd. 10
starting part of the rising slope (or descending slope) through the zero point
(intermediate value of amplitude) to the ending point of the rising slope (or
descending slope) through the zero point (intermediate value of amplitude).
However, the measurement interval which determines the maximum
voltage or current is within the overall data updating cycle. Therefore, the
measurement of Ipk+, Ipk-, Upk+, Upk-, Ucf and Icf calculated based on the
maximum voltage and current also adopts the data updating cycle as the
measurement interval.
The rising or descending edge is selected automatically to prolong the
measurement interval.
If there is only one or no rising slope or descending slope within the data
updating cycle, the data updating cycle is taken as the measurement
interval.
The input signal to be used as the synchronization source can be set in
each unit (for synchronization with the zero point of that input signal). The
overall interval of the signal voltage, current or data updating cycle can be
selected as the synchronization source for measurement.
NOTE
The data updating cycle refers to the cycle used for calculating sampling data of the
measurement function. It is identical to the set value of the data updating rate.
The slope refers to signal changes from low level to high level (rising edge) or from high level to
low level (descending edge).
Measurement interval for harmonic measurement
At the sampling frequency of harmonic measurement, the measurement interval
refers to the first point 1024 from the data updating cycle. The sampling
frequency of harmonic measurement is determined automatically by the signal
cycle set as the PLL source in the instrument. The sampling data or
measurement interval for calculation may be different from the sampling data or
measurement interval of the measurement function in conventional
measurement.

Measurement Conditions
Copyright © Itech Electronics Co., Ltd. 11
2.3 Setting of Filter and Crest Factor
Operation steps
1. Select Menu > SET UP > OTHER SET and enter the OTHER configuration
page.
2. Press to select the parameter to be configured (blue font background),
and then press the soft key corresponding to the parameter on the right to set
the required value, as shown in the following diagram.
Character
Function description
Sync Source
Select the synchronization source: U/I/OFF. The overall
interval of the signal voltage, current or data updating cycle
can be selected as the synchronization source for
measurement.
Freq Filter
Set the status of the frequency filter. When “ON” is selected,
the frequency filter is turned on. When “OFF” is selected, the
frequency filter is turned off.
Line Filter
Set the status of theline filter. When “ON” is selected, the line
filter is turned on. When “OFF” is selected, the line filter is
turned off.
Crest Factor
Set the crest factor: CF3/CF6
Update Rate
Data Updating Rate Setting key: when this key is pressed, the
capture interval of the voltage, current, power and other data,
i.e. data updating rate, can be set. When the data updating
rate is increased, rapid load changes of the power system can
be obtained. When the data updating rate is decreased,
relative low-
frequency signals can be measured. Options of
the data updating rate: 0.1s/0.25s/0.5s/1s/2s/5s
3. Press the Enter key to save the settings.
Filter Frequency filter: it is inserted in the frequency measurement circuit and may
affect frequency measurement. It can be used for filtering high-frequency
components of interference to make the measured frequency parameter more
accurate. When the frequency filter is switched on, the voltage or current of no
more than 200Hz can be measured. The cutoff frequency is 500HZ.

Measurement Conditions
Copyright © Itech Electronics Co., Ltd. 12
Line filter: it is inserted in the voltage and current measurement circuit and has
direct influence on measurement of the voltage, current and power. When the
line filter is switched on, noise and high-frequency components from the inverter
or distortion waveform can be filtered. The cutoff frequency is 500HZ.
Crest factor The crest factor is the ratio of the waveform peak to the effective value. The
crest factor of IT9121 is specified as the times of the crest value which can be
input under the rated input conditions. The crest factor CF3 or CF6 can be
selected in the interface “Menu > SETUP > OTHER SET”.
rangetMeasuremen inputbecanwhichPeak value
)(factorCrest =CF
The crest factor can be set as 3 or 6. The crest factor can be measured under
the following conditions:
{ }
value)(effectivevalueMeasured 6)or(3CFofSet valuerangetMeasuremen
factorCrest × =）（CF
NOTE
The crest value of the input signal must be no more than the maximum allowable
input value.
When the crest factor of the measured signal is larger than the crest factor in
instrument specifications (based on the crest value of rated input), the signal
with the crest factor larger than the specified value can be measured by setting
a range including the value of the measured signal.
For example, when CF is set as 3 but the measured value (effective value) is
less than 60% of the range, the signal with CF more than 5 can be measured.
When CF is 3, the signal with CF equal to 300 can be measured under
minimum effective input (1% of the range) conditions.
The voltage range, current range, effective input range and measurement
accuracy depend on the set crest factor.
2.4 Setting of Averaging Function
The user can set the averaging function via this menu. When the input signal
frequency is low, the value is displayed unstably and cannot be read easily. In
this case, the averaging function can be enabled to calculate and display the
average value of several measurements.
Operation steps
1. Select Menu > SET UP > AVERAG SET to enter the configuration page of
the averaging function.
2. Press to select the parameter to be configured (blue font
background), and then press the soft key corresponding to the parameter on
the right to set the required value, as shown in the following diagram.