Tonghui TH1942 User manual

OPERATION MANUAL
TH1942
50000 CountMultimeter
Changzhou Tonghui Electronic Co., Ltd.
www.tonghui.com.cn

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Manual Printing History
The manual printing data and part number indicate its current edition. The printing date changes when a
new edition is printed. The manual part number changes when extensive technical changes are
incorporated.
October 2008……………………………First Edition
Notice
The information contained in this document is subject to change without notice.
Safety notice supplement
As described in the International Electrotechnical Commission (IEC) Standard IEC 664,
digital multimeter measuring circuits (e.g., Tonghui Models 1951, 1961, 1941, and 1942)
are Installation Category II. All other instruments‘signal terminals are Installation Category I
and must not be connected to mains.
This equipment is POLLUTION DEGREE 2, INDOOR USE product.
Safety Precautions
Users of this product must be protected from electric shock at all times. The responsible
body must ensure that users are prevented access and/or insulated from every connection
point. In some cases, connections must be exposed to potential human contact. Product
users in these circumstances must be trained to protect themselves from the risk of electric
shock. If the circuit is capable of operating at or above 1000 volts, no conductive part of the
circuit may be exposed.

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Before operating an instrument, make sure the line cord is connected to a properly
grounded power receptacle. Inspect the connecting cables, test leads, and jumpers for
possible wear, cracks, or breaks before each use.
For maximum safety, do not touch the product, test cables, or any other instruments while
power is applied to the circuit under test. ALWAYS remove power from the entire test
system and discharge any capacitors before: connecting or disconnecting cables or
jumpers, or making internal changes, such as installing or removing jumpers.
Do not touch any object that could provide a current path to the common side of the circuit
under test or power line (earth) ground. Always make measurements with dry hands while
standing on a dry, insulated surface capable of withstanding the voltage being measured.
The instrument and accessories must be used in accordance with its specifications and
operating instructions or the safety of the equipment may be impaired.
Do not exceed the maximum signal levels of the instruments and accessories, as defined in
the specifications and operating information, and as shown on the instrument or test fixture
panels.
When fuses are used in a product, replace with the same type and rating for continued
protection against fire hazard.
Chassis connections must only be used as shield connections for measuring circuits, NOT
as safety earth ground connections.
If you are using a test fixture, keep the lid closed while power is applied to the device under
test.

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Contents
Chapter 1 General Information............................................................................................................................. 7
1.1 Feature Overview......................................................................................................................................... 7
1.2 Operating Environment ............................................................................................................................... 7
1.3 Dimensions and Weight............................................................................................................................... 7
1.4 Safety symbols and Precautions .................................................................................................................. 8
1.5 Incoming Inspection .................................................................................................................................... 8
1.6 Warranty....................................................................................................................................................... 9
1.7 Limitation of Warranty ................................................................................................................................ 9
Chapter 2 TH1942 Overview............................................................................................................................... 10
2.1 Front Panel Summary ................................................................................................................................ 10
2.2 Annunciators on Screen..............................................................................................................................11
2.3 Front Panel Menu Reference ..................................................................................................................... 12
2.4 Front Panel Menu Overview...................................................................................................................... 13
2.5 Rear Panel Summary ................................................................................................................................. 14
2.6 Power up.................................................................................................................................................... 15
2.6.1 Power Line Connection.............................................................................................................. 15
2.6.2 Input Terminals............................................................................................................................ 15
2.6.3 Power-up Sequence................................................................................................................... 16
2.6.4 High Energy Circuit Safety Precautions .................................................................................. 16
2.6.5 Power-on Defaults....................................................................................................................... 17
2.6.6 Warm-up time.............................................................................................................................. 17
2.7 Display....................................................................................................................................................... 17
Chapter 3 Basic Measurements ......................................................................................................................... 18
3.1 Preparation................................................................................................................................................. 18
3.2 Measuring Voltage..................................................................................................................................... 18
3.2.1 Connections................................................................................................................................. 18
3.3 Measuring Current..................................................................................................................................... 19
3.3.1 Connections................................................................................................................................. 19
3.3.2 Front Panel Fuse Replacement................................................................................................ 21
3.4 Measuring Resistance................................................................................................................................ 22
3.4.1 Connections................................................................................................................................. 22
3.4.2 Shielding....................................................................................................................................... 22
3.5 Measuring Frequency and Period.............................................................................................................. 23
3.5.1 Trigger Level and Measurement Errors................................................................................... 23
3.5.2 Gate Time..................................................................................................................................... 23
3.5.3 Connections................................................................................................................................. 23
3.6 Measuring Continuity................................................................................................................................ 24
3.6.1 Connections................................................................................................................................. 24
3.7 Testing Diode............................................................................................................................................. 25
3.7.1 Connections................................................................................................................................. 25
3.8 Measuring True RMS AC+DC .................................................................................................................. 26
3.8.1 Connections................................................................................................................................. 26

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3.8.2 Using the 2nd parameter display ............................................................................................... 27
3.9 Math Functions.......................................................................................................................................... 27
3.9.1 Percent ......................................................................................................................................... 27
3.9.2 dB Calculation.............................................................................................................................. 28
3.9.3 dBm Calculation.......................................................................................................................... 29
Chapter 4 Measurement Options....................................................................................................................... 31
4.1 Measurement configuration....................................................................................................................... 31
4.1.1 Range ........................................................................................................................................... 31
4.1.2 Relative......................................................................................................................................... 32
4.1.3 Rate............................................................................................................................................... 32
4.2 Trigger Operations..................................................................................................................................... 33
4.2.1 Trigger flow................................................................................................................................... 33
4.2.2 Reading Hold............................................................................................................................... 34
4.3 MAX / MIN............................................................................................................................................... 34
4.4 Limit Operations........................................................................................................................................ 35
4.4.1 Enabling limits.............................................................................................................................. 35
4.4.2 Setting Limit Values.................................................................................................................... 35
4.5 System Operations..................................................................................................................................... 36
4.5.1 Beeper Control ............................................................................................................................ 36
4.5.2 Baud rate...................................................................................................................................... 36
4.5.3 Selecting the Terminal Character.............................................................................................. 37
4.5.4 Key Sound.................................................................................................................................... 37
Chapter 5 Remote Operation.............................................................................................................................. 39
5.1.1 RS-232.......................................................................................................................................... 39
5.2 RS-232 Interface Operation....................................................................................................................... 39
5.2.1 RS-232 Connection .................................................................................................................... 39
5.2.2 Sending and receiving data....................................................................................................... 40
5.2.3 Selecting Baud Rate................................................................................................................... 41
5.2.4 Software Protocol........................................................................................................................ 41
5.3 Data Format............................................................................................................................................... 42
Chapter 6 SCPI Command Reference.............................................................................................................. 43
6.1 Command structure.................................................................................................................................... 43
6.2 Command Syntax....................................................................................................................................... 43
6.2.1 Commands and command parameters ................................................................................... 43
6.2.2 Short-form Rules......................................................................................................................... 45
6.2.3 Basic Rules of Command Structure......................................................................................... 45
6.2.4 Multiple Command Rules........................................................................................................... 46
6.2.5 Command Path Rules................................................................................................................ 46
6.3 Command Reference ................................................................................................................................. 46
6.3.1 DISPlay subsystem..................................................................................................................... 46
6.3.2 FUNCtion subsystem.................................................................................................................. 48
6.3.3 VOLTage subsystem................................................................................................................... 49
6.3.4 CURRent subsystem.................................................................................................................. 53
6.3.5 RESIister subsystem.................................................................................................................. 57

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6.3.6 FREQuency and PERiod subsystem....................................................................................... 60
6.3.7 HOLD subsystem........................................................................................................................ 62
6.3.8 TRIGger subsystem.................................................................................................................... 64
6.3.9 FETCH Subsystem..................................................................................................................... 64
6.3.10 Common Commands ............................................................................................................... 65
Chapter 7 Specifications...................................................................................................................................... 66
Chapter 8 Program Examples............................................................................................................................. 71

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Chapter 1 General Information
Thanks very much for choosing and using our product. If you have any questions after reviewing this
manual, please contact your local representative or call directly to our application engineers for further
consultation.
1.1 Feature Overview
TH1942 is a 50000 count digital multimeter with high accuracy, stability and speed. The multimeter can
provides a maximum measurement speed of 25 readings/sec. TH1942 has 0.01% DC voltage basic
accuracy, 0.03% basic resistance accuracy and other high performance. TH1942 has broad
measurement ranges:
DC voltage from 10μV to 1000V
AC (RMS) voltage from 10μV to 750V, 1000V Peak
DC current from 100nA to 20A
AC (RMS) current from 100nA to 20A
Two and four-wire resistance from 10mΩ to 50MΩ
Frequency from 5Hz to 1MHz
Some additional capabilities of Model TH1942:
Full range of functions: In addition to those listed above, The TH1942 functions include period,
dB, dBm, continuity, diode testing, max, min and percent.
Programming languages and remote control interfaces: The TH1942 provides the SCPI
programming language and the remote control interface port: RS-232C.
Closed-cover calibration: The multimeter can be calibrated either from the front panel or remote
interface.
1.2 Operating Environment
Power supply: 110V/220V ±10%
Line frequency: 50Hz / 60Hz ±5%
Power consumption: <10VA
Operating temperature: 0℃to 40℃
Humidity: ≤ 90%RH
1.3 Dimensions and Weight
Dimensions（W ×H×D ） ： 225mm×100mm×318mm
Net weight:Around 2.2Kg

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1.4 Safety symbols and Precautions
The symbol on the instrument indicates that user should refer to the operating instructions located
in the manual before performing.
The symbol on the instrument shows that high voltage may be present on the terminal(s). Be
careful to avoid personal contact with these voltages.
The symbol on the instruments means earth grounding.
The WARNING heading used in the manual explains high voltage danger that might result in personal
injury or death. Always read the associated information very carefully before performing the indicated
procedure.
The CAUTION heading in the manual reminds user that hazards could damage the instruments if not
according to operating instructions. Such damage may invalidate the warranty.
1.5 Incoming Inspection
The TH1942 was carefully inspected mechanically and electrically before shipment. After unpacking all
items from the shipping carton, please check for any obvious signs of physical damage that may have
occurred during transportation. Report any damage to the shipping agent immediately. Save the original
packing carton for possible future reshipment. The following items are included with every Model
TH1942 order:
Model TH1942 50000 Count Multimeter
Test leads (Model TH26036)
Power cord
Two 500mA fuses
Two 1A fuses
Operation Manual
Quality and warranty certificate
Test report
Other optional accessories if ordered
Verify that you have received all the items above when you get multimeter. If anything is missing, please
contact our representative or our sales office.

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1.6 Warranty
Tonghui warrants this product to be free from defects in material and workmanship for a period of 2 years
from the date of shipment. During the warranty period, we will, at our option, either repair or replace any
product that proves to be defective.
1.7 Limitation of Warranty
This warranty does not apply to defects resulting from product modification without our express written
consent, or misuse of any product or part. This warranty also does not apply to fuses, software, or
problems arising from normal wear or failure to follow instructions.
THIS WARRANTY IS IN LIEU OF ALL OTHER WARRANTIES, EXPRESSED OR IMPLIED, INCLUDING ANY
IMPLIED WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR USE. THE REMEDIES
PROVIDED HEREIN ARE BUYER’S SOLE AND EXCLUSIVE REMEDIES.
NEITHER TONGHUI ELECTRONICS NOR ANY OF ITS EMPLOYEES SHALL BE LIABLE FOR ANY DIRECT,
INDIRECT, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OF ITS
INSTRUMENTS AND SOFTWARE EVEN IF TONGHUI ELECTRONICS HAS BEEN ADVISED IN ADVANCE
OF THE POSSIBILITY OF SUCH DAMAGES. SUCH EXCLUDED DAMAGES SHALL INCLUDE, BUT ARE
NOT LIMITED TO: COSTS OF REMOVAL AND INSTALLATION, LOSSES SUSTAINED AS THE RESULT OF
INJURY TO ANY PERSON, OR DAMAGE TO PROPERTY.

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Chapter 2 TH1942 Overview
2.1 Front Panel Summary
The front panel of the TH1942 is shown in Figure 2-1. This figure includes some important abbreviated
information that should be reviewed before operating the instrument.
！CATⅠ(1000V)
CATⅡ(300V)Ω
COM
20A
T1AL 250V ALL INPUT
1KV MAX
500mA
MAX
V
1000V
MAX
DC I AC I
Period
dB dBm
%Comp
Hold
Menu Local
2nd
DC V AC V
ΩFreq
AC+DC
Rel
Rate
Esc Shift
Trig
Auto
mA
DC
AC
MEDFAST SLOW RELHOLDTRIG MATHAUTO
DC
AC
COMP AUTO MAX MIN SHIFTRMTIN LOHI ERR
POWER
ON OFF
50000 Count Multimeter
TH1942
Figure 2-1 TH1942 Front Panel
1. Measurement Function keys (shifted and unshifted)
Select measurement function: DC voltage and current, AC voltage and current, resistance,
continuity, frequency, period, dB, dBm, True RMS AC+DC and diode test.
2. Math function keys
Select the math function: Rel, %, Max/Min, Comp and Hold.
3. 2nd Display and speed key
Changes reading rate: Fast, Medium and Slow.
+ turn on or off the 2nd parameter display.
4. Menu operation keys
Shift
→Open/Close menu
Move through selections within menu level, command level or parameter level
Move through selections within menu level, command level or parameter level.
Move up a level.
Move down a level.
(ENTER) Save the change made on ―parameter‖level, and return to the ―command‖level.
Cancel the change made on ―parameter‖ level, and return to the ―command‖level.
5. Range and Combination function selecting keys
Select a 2nd display parameter
Select a 2nd display parameter
Primary
Display
Secondary
Display
On /off
Switch
Current
Input fuse
Input terminals
5. Range
Selection
1. Function keys
2. Math function keys
4. Menu
Operation
3. 2nd Display
And speed keys
7. Shift/local
Keys
6. Hold/Trig
Keys