Tonghui TH1941 Operation Manual
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Tonghui TH1941 Operation Manual

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OPERATION MANUAL
TH1941
1
4
/
Digit Multimeter
2
Changzhou Tonghui Electronic Co., Ltd.
www.tonghui.com.cn

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  • Page 1 OPERATION MANUAL TH1941 Digit Multimeter Changzhou Tonghui Electronic Co., Ltd. www.tonghui.com.cn...
  • Page 2 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.
  • Page 3 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.

  • Page 4: Table Of Contents

    1.4 Safety symbols and Precautions ........................8 1.5 Incoming Inspection ............................ 8 1.6 Warranty............................... 9 1.7 Limitation of Warranty ..........................9 Chapter 2 TH1941 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 ........................
  • Page 5 3.8.2 Using the 2 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 ............................
  • Page 6 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...

  • Page 7: Chapter 1 General Information

    Feature Overview TH1941 is a 4½ digital multimeter with high accuracy, stability and speed. The digital multimeter provides a maximum measurement speed of 25 readings/sec. TH1941 has a 0.01% DC voltage basic accuracy, 0.03% basic resistance accuracy and other high performance. TH1941 has broad measurement ranges: ...

  • Page 8: Safety Symbols And Precautions

    Such damage may invalidate the warranty. Incoming Inspection The TH1941 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.

  • Page 9: Warranty

    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.

  • Page 10: Chapter 2 Th1941 Overview

    Chapter 2 TH1941 Overview Front Panel Summary The front panel of the TH1941 is shown in Figure 2-1. This figure includes some important abbreviated information that should be reviewed before operating the instrument. 2. Math function keys 1. Function keys...

  • Page 11: Annunciators On Screen

    Select a higher range and disable auto ranging. Select a lower range and disable auto ranging. Toggle between auto ranging and manual ranging. Trig/Hold Key Trigger a measurement from the front panel. Trig → Shift Trig Hold a stable reading on the display when selected numbers of samples are within the selected tolerance.

  • Page 12: Front Panel Menu Reference

    Front Panel Menu Reference A：MATH MENU 1: HI LIMIT → 2: LO LIMIT → 3: PERC REF → 4: dB REF→ 5: dBm REF 1. HI LIMIT Set the high limit for limit testing. 2. LO LIMIT Set the low limit for limit testing. 3.

  • Page 13: Front Panel Menu Overview

    Front Panel Menu Overview The menu is organized in a top-down tree structure with three levels (menus, commands and parameters) as shown in Figure 2-3. You can use down ( ) or up ( ) to move menu tree from one level to another.

  • Page 14: Rear Panel Summary

    Rear Panel Summary The rear panel of TH1941 is shown in Figure 2-4. This section includes important information that should be reviewed before operating the instrument. RS-232C 10VA Max WARNING TO AVOID ELECTRIC SHOCK, RATING FUSE THE POWER CORD PROTECTIVE GROUNDING 贴标签...

  • Page 15: Power Up

    Power Line Connection Follow the procedure below to connect the TH1941 to line power and turn on the instrument. Check to make sure that the line voltage is in the range of 198V to 242V (or 110V± 10%) and line frequency is in the range of 47.5 to 52.5Hz (or 60Hz±...

  • Page 16: Power-Up Sequence

    ADRS MAX MIN SHIFT On power-up, Model TH1941 performs self-tests on its EPROM and RAM and lights all segments and annunciators for about 1 second. If a failure is detected, the instrument momentarily displays an error message and the ERR annunciator turns on.

  • Page 17: Power-On Defaults

    Display The display of Model TH1941 is primarily used to display readings, along with the units and type of measurement. Annunciators located on the left, right and bottom indicate various states of operation.

  • Page 18: Chapter 3 Basic Measurements

    AC technique: true RMS, ac-coupled, 1000V Peak AC 3.2.1 Connections Assuming Model TH1941 is under factory default conditions, the basic procedure is as follows: 1. Connect test leads to and COM terminals. 2. Select DC or AC voltage measurement by pressing 3.

  • Page 19: Measuring Current

    Model TH1941 current measurement range: 2mA, 20mA, 200mA (DC only), 2A, 20A Maximum resolution: 100nA (on 2mA range) 3.3.1 Connections Assuming Model TH1941 is under factory default conditions, the basic procedure is as follows: 1. Connect test leads between 500mA terminal and COM or between 20A terminal and COM. → →...
  • Page 20 6. press to turn on the 2nd parameter display , Use key to move across display parameters 7. Take readings from the display. DC I AC I TH1941 Digit Multimeter DC V AC V 1000V Ⅰ( Ω ！...

  • Page 21: Front Panel Fuse Replacement

    DC I AC I TH1941 DC V AC V Digit Multimeter Ⅰ( 1000V Ω ！ Ⅱ( 300V Period AUTO Ω Freq 500mA 1000V AC+DC Comp Hold Rate Trig Menu Local Auto T1AL 250V ALL INPUT Shift 1KV MAX CURRENT SOURCE...

  • Page 22: Measuring Resistance

    Model TH1941 Resistance measurement range: 200Ω, 2kΩ, 20kΩ, 200kΩ, 2MΩ, 20MΩ; Maximum resolution: 10mΩ (on 200Ω range) 3.4.1 Connections Assuming Model TH1941 is under factory default conditions, the basic procedure is as follows: 1. Connect the test leads between and COM. 2. Select resistance measurement function by pressing 3.

  • Page 23: Measuring Frequency And Period

    The error will be no more than +/-1 from the total gate counts, this assures an equivalent accuracy over the whole frequency range. 3.5.2 Gate Time Gate time is the amount of time TH1941 uses to sample frequency or period readings. The measurement speed rate and the measuring frequency change the gate time. 3.5.3 Connections Assuming Model TH1941 is under factory default conditions, the basic procedure is as follows: 1.

  • Page 24: Measuring Continuity

    <100kΩ 20.000MΩ <1MΩ 3.6.1 Connections Assuming Model TH1941 is under factory default conditions, the basic procedure is as follows: 1. Connect test leads to and COM terminals. → 2. Select Continuity measurement function by pressing 3. Connect test leads to the resistance under test as shown in Figure 3-5.

  • Page 25: Testing Diode

    Figure 3-5 Continuity Measurement Testing Diode Model TH1941 can also be used to measure the forward voltage drop of general-purpose diodes and the zener voltage of zener diodes. A current range of 0.5mA will be selected for diode measurement. Note: Diode test has a non-selectable reading rate of Medium 3.7.1...

  • Page 26: Measuring True Rms Ac+Dc

    AC+DC RMS value by using the following formula:    3.8.1 Connections Assuming Model TH1941 is under factory default conditions, the basic procedure is as follows: 1. Connect test leads to and COM terminals, as shown in Figure 3-7. → → 2. Press...

  • Page 27: Using The 2 Nd Parameter Display

    (Measuring value) Max/Min (Measuring value) Note: The measurement range is determined by main measurement function when a 2 parameter is displayed.. Math Functions Model TH1941 math operations are divided into three categories:  percent  dB and dBm calculations ...

  • Page 28: Db Calculation

    Model TH1941 will display measurement result of calculation. If the value of ―Input‖ is larger than that of ―Reference‖, displayed result will be positive; contrarily, it will be negative if the value of ―Input‖ is smaller than that of ―Reference‖.

  • Page 29: Dbm Calculation

    1mW reference. With user-programmable reference impedance, Model TH1941 reads 0dBm when the voltage needed to dissipate 1mW through the reference impedance is applied. The relationship between dBm, reference impedance, and the voltage is defined by the following equation: ...
  • Page 30 (ENTER) to confirm the reference value, the message ―SAVED‖ will be displayed for a 5. Press moment, and TH1941 will return to the command level. Press to cancel the reference value input, TH1941 returns back to the command level without changing the reference value. → 6. Press Shift key to exit the menu and return to the dB math operation status.

  • Page 31: Chapter 4 Measurement Options

    Chapter 4 Measurement Options This chapter provides description of the front panel features of TH1941. For those measurement options accessible only by a remote interface, refer to Chapter 5 and 6. This chapter is organized as follows:  Measurement Configuration – Describes Ranging, Relative readings, Digits of Resolution and Measurement rate Triggering operations –...

  • Page 32: Relative

    The relative operation could be used to null offsets or subtract a baseline reading from present and future readings. When relative function is enabled, Model TH1941 uses the present reading as a relative value. Subsequent readings will be the difference between the actual input value and the relative value.

  • Page 33: Trigger Operations

    IMM, MAN or BUS trigger source. (ENTER) to confirm the choice. The message ―SAVED‖ will be displayed to show that 7. Press the change is now in effect. TH1941 automatically exits the parameter level and moves up a level to the command level. Measurement Sample The primary measurement sample action is a measurement.

  • Page 34: Reading Hold

    Enter a value of count (from 2 to 100). (ENTER) to confirm the count. The message ―SAVED‖ will be displayed to show that 12. Press the change is now in effect. TH1941 will exit the parameter level and move up a level to the command level. →...

  • Page 35: Limit Operations

    (ENTER) to confirm the value of high limit. The message ―SAVED‖ will be displayed to Press show that the change is now in effect. TH1941 will exit the parameter level and move up a level to the command level. key to move across to the LOW LIMIT command, ―2: LO LIMIT‖ will be displayed.

  • Page 36: System Operations

    ON or OFF. (ENTER) to confirm the beeper control. The message ―SAVED” will be displayed to Press show that the change is now in effect. TH1941 will exit the parameter level and move up a level to the command level. →...

  • Page 37: Selecting The Terminal Character

    (ENTER) to confirm the selection. The message ―SAVED‖ will be displayed to show Press that the change is now in effect. TH1941 will exit the parameter level and move up a level to the command level. →...
  • Page 38 ON or turn OFF the key sound. (ENTER) to confirm the selection. The message ―SAVED‖ will be displayed to show Press that the change is now in effect. TH1941 will exit the parameter level and move up a level to the command level. →...

  • Page 39: Chapter 5 Remote Operation

    Chapter 5 Remote Operation Besides the front panel control, TH1941 supports RS-232 serial interface for remote control. Standard Commands for Programmable Instruments (SCPI) is fully supported to communicated with computer via the RS-232 interfaces, with a certain communication protocols. RS-232 You can connect RS-232 interface with a computer.

  • Page 40: Sending And Receiving Data

    Pin 4 and 6, pin 7 and 8 are shorted respectively at the end of controller. 5.2.2 Sending and receiving data Model TH1941 transfers data using 8 data bits, 1 stop bit, and no parity. Each program message that is transmitted to the controller is terminated with <LF> or <CR>.

  • Page 41: Selecting Baud Rate

    (ENTER) to confirm the selection. The message ―SAVED‖ will be displayed to show Press that the change is now in effect. TH1941 will exit the parameter level and move up a level to the command level. →...

  • Page 42: Data Format

    TH1941 only sends information under following two conditions. The first is when a character is received normally; TH1941 will send the character back as a handshake. The second is when a query command is received; TH1941 will send the query response information.

  • Page 43: Chapter 6 Scpi Command Reference

    IEEE std. 488.2-1987, and these commands are common for all devices. Not all commands are supported by the TH1941. The SCPI commands are used to control all of the TH1941's functions. The SCPI commands are tree structured three levels deep. (The highest level commands are called the subsystem commands in this manual.) So the lower level commands are legal...
  • Page 44  Brackets [ ]: Some command words are enclosed in brackets. These brackets are used to denote an optional command word that does not need to be included in the program message. For example: :RANGe[:UPPer] <n> These brackets indicate that :UPPer is optional and does not have to be used. Thus, the above command can be sent in one of the two ways below: :RANGe <n>...

  • Page 45: Short-Form Rules

    <n> Numeric value: A numeric value parameter can consist of a NRf number or one of the following name parameters: DEFault, MINimum, MAXimum. When DEFault parameter is used, the instrument is programmed to the *RST default value. When the MINimum parameter is used, the instrument is programmed to the lowest allowable value.

  • Page 46: Multiple Command Rules

    ◆ HOLD ◆ TRIGer ◆ FETCh Model TH1941 supports following common commands: ◆ *RST ◆ *TRG ◆ *IDN 6.3.1 DISPlay subsystem The DISPlay subsystem commands are mainly used to control the display of the TH1941. and are summarized in Table 6-2.
  • Page 47 Table 6-1 DISPlay Subsystem Commands Summary Command Function Description :DISPlay :ENABle <b> Enable or disable front panel dispaly :ENABle? Query state of the display :ENABle <b> Command syntax: :DISPlay:ENABle <b> Command Parameter: <b> = 0 or OFF Disable front panel display 1 or ON Enable front panel display Query:...

  • Page 48: Function Subsystem

    6.3.2 FUNCtion subsystem The commands in this subsystem are used to configure the measurement function subsystems and are summarized in Table 6-2. Table 6-2 FUNCtion Subsystem Commands Summary 命令 功能简述 Select measurement function ： ‗VOLTage:AC‘, ‗VOLTage:DC‘, :FUNCtion <name> ‗RESistance‘, ‗FRESistance‘, ‗CURRent:AC‘, ‗CURRent:DC‘, ‗FREQuency‘, ‗PERiod‘, ‗DIODe‘, ‗CONTinuity‘.

  • Page 49: Voltage Subsystem

    6.3.3 VOLTage subsystem The commands in this subsystem are used to configure and control voltage measurement function and are summarized in Table 6-3. Table 6-3 VOLTage Subsystem Commands Summary Command Function Description Default :VOLTage:DC Path to configure DC voltage :NPLCycles <n> Set integration rate (line cycle;...
  • Page 50 MINimum MAXimum Query: :NPLCycles? Query programmed NPLC value Description: The integration period (measurement speed) for the basic measurement functions (except Frequency and Period) is set using the:NPLCycles command. NPLC(Number of Power Line Cycles) expresses the integration period by basing it on the power line frequency. For example, for a PLC of 1, the integration period in seconds would be1/60 (for 60Hz line power) which is 16.67 msec.
  • Page 51 Query: :AUTO? Query auto range (ON or OFF) Description: These command are used to control auto ranging. With auto ranging enabled, the instrument automatically goes to the most sensitive range to perform the measurement. The auto range command (:RANGe:AUTO) is coupled to the command that manually selects the measurement range (:RANGe <n>).
  • Page 52 :VOLTage:AC:REFerence:STATe <b> Control reference for ACV :VOLTage:DC:REFerence:STATe <b> Control reference for DCV Command parameter: <b> = 1 or ON Enable reference 0 or OFF Disable reference Query: :STATe? Query state of reference. Description: These commands are used to enable or disable Reference for the specified function. When enabled, the displayed reading will include the programmed reference value.

  • Page 53: Current Subsystem

    6.3.4 CURRent subsystem The commands in this subsystem are used to configure and control current measurement function and are summarized in Table 6-4. Table 6-4 CURRent Subsystem Commands Summary Command Function Description Default :CURRent:DC Path to configure DC current :NPLCycles <n> Set integration rate(line cycles;...
  • Page 54 DEFault MINimum MAXimum Query: :NPLCycles? Query programmed NPLC value Description: The integration period (measurement speed) for the basic measurement functions (except Frequency and Period) is set using the:NPLCycles command. NPLC(Number of Power Line Cycles) expresses the integration period by basing it on the power line frequency. For example, for a PLC of 1, the integration period in seconds would be1/60 (for 60Hz line power) which is 16.67 msec.
  • Page 55 Query: :AUTO? Query auto range (ON or OFF) Description: These command are used to control auto ranging. With auto ranging enabled, the instrument automatically goes to the most sensitive range to perform the measurement. The auto range command (:RANGe:AUTO) is coupled to the command that manually selects the measurement range (:RANGe <n>).
  • Page 56 :STATe <b> Command syntax: : CURRent:AC:REFerence:STATe <b> Control reference for ACI : CURRent:DC:REFerence:STATe <b> Control reference for DCI Command parameter: <b> = 1 or ON Enable reference 0 or OFF Disable reference Query: :STATe? Query state of reference. Description: These commands are used to enable or disable Reference for the specified function. When enabled, the displayed reading will include the programmed reference value.

  • Page 57: Resiister Subsystem

    6.3.5 RESIister subsystem The commands in this subsystem are used to configure and control resistance measurement function and are summarized in Table 6-5. Table 6-5 RESIister Subsystem Commands Summary Command Function Description Default :RESistance Path to configure resistance :NPLCycles <n> Set integration rate (line cycles: 0.5 to 2) :NPLCycles? Query line cycle integration rate...
  • Page 58 :RANGe Commands :[UPPer] <n> Command syntax: Set measurement range for Ω :RESistance:RANGe[:UPPer] <n> Command Parameter: <n> = 0 to 20e6 Expected reading is ohms DEFault 20e6 (Ω) MINimum 0 (All functions) MAXimum Same as DEFault Query: :RANGe[:UPPer]? Query measurement range of the current function. Description: This command is used to manually select the measurement range for the specified measurement function.
  • Page 59 :REFerence <n> Commands :REFerence <n> Command syntax: Specify reference for Ω :RESistance:REFerence <n> Command parameter: Reference for Ω <n> = 0 to 20e6 DEFault 923107715guozhigang 0 (All measurement functions) MINimum Mininum value for specified function MAXimum Maximum value for specified function Query: :REFerence? Query reference for relative function...

  • Page 60: Frequency And Period Subsystem

    Description: When one of these commands is sent, the measurement input signal is acquired and established as the reference value. This command is typically used to zero the display. For example, if the instrument is displaying a 0.1Ω offset, sending this command and enabling Reference zeroes the display.
  • Page 61 Command parameter: <n> = 0 to 1010 Specify signal levels in volts (voltage threshold) Query: :RANGe? Query maximum signal level. Description: These commands are used to specify the expected input level. The instrument will then automatically select the most sensitive current or voltage threshold range. :REFerence <n>...

  • Page 62: Hold Subsystem

    Command parameter: <b> = 1 or ON Enable reference 0 or OFF Disable reference Query: :STATe? Query state of reference. Description: These commands are used to enable or disable Reference for the specified function. When enabled, the displayed reading will include the programmed reference value. When disabled, the displayed reading will not include the reference value.
  • Page 63 :WINDow <NRf> Command syntax: :HOLD:WINDow <NRf> Command Parameter: <NRf> = 0.01 to 10 Set window (percent) Query: :WINDow? Query Hold window Description: This command is used to set the window for HOLD. This window is expressed as a percent of the ―seed‖...

  • Page 64: Trigger Subsystem

    6.3.8 TRIGger subsystem These commands in this subsystem are used to configure and control trigger measurement function and are summarized in Table 6-8. Table 6-8 TRIGger Subsystem Commands Summary Command Function Description Default :TRIGger :SOURce <name> Select control source IMMediate :SOURce? Query control source :TRIGger...

  • Page 65: Common Commands

    Common commands can be used to all equipments. We provide some common commands as below: *RST Command Syntax: *RST Description: Reset the instrument *TRG Command Syntax: *TRG Description: Trigger the instrument for measurement *IDN? Query Syntax: *IDN? Query return: <product>,<version><LF^END> Here: <product> TH1941 Digital Multimeter <version> Ver1.0 Description: Query information returned to instrument...

  • Page 66: Chapter 7 Specifications

    Chapter 7 Specifications Introduction Chapter 7 describes the complete specifications of the Model TH1941 Multimeter. Technical Specifications Specifications Assumptions  One year calibration cycle.  Operating temperature at 18℃ to 28℃  Accuracy is expressed as: ± (% of reading + digits) after 30 minutes‘ warm-up.
  • Page 67 DC Voltage Resolution, Full Scale reading and Accuracy Typical Full Scale Accuracy Rate Range Resolution Input Reading (1 year) Impedance 200.00mV 1 0μV 210.00 >10MΩ 0.03%+0.04% 2.0000 V 10 0μV 2.1000 0.03%+0.02% >11.1MΩ Slow 20.000V 21.000 0.03%+0.02% >10.1MΩ 200.00 V 10 mV 210.00 0.03%+0.02%...
  • Page 68 DC Current Full Scale Accuracy Burden Voltage Rate Range Resolution Reading (1 year) & Shunt Resistor 0.1 μA <0.3V / 100Ω 2.0000mA 2.1000 0.08 +0.025 1μA <0.04V / 1Ω 20.000mA 21.000 0.08 +0.02 10μA <0.3V / 1Ω Slow 200.00mA 210.00 0.08 +0.02 <0.05V / 10mΩ...
  • Page 69 Resistance Full Scale Accuracy Rate Range Resolution Test Current Reading (1 year) 200.00Ω 10mΩ 210.00 0.5 mA 0.10 +0.05 2.0000 kΩ 100mΩ 2.1000 0.45 mA 0.10 +0.025 20.000kΩ 1Ω 45μA 21.000 0.10 +0.025 Slow 200.00 kΩ 10 Ω 4.5μA 210.00 0.10 +0.025 2.0000MΩ...
  • Page 70 Period Frequency Full Scale Input Sensitivity Resolution Accuracy Range Range Reading (Sine Wave) 1~10μs 0.1ns 9.9999 500mV rms 0.01 +0.008 100mV 10μs~10ms 9.9999 300mV rms 0.01 +0.008 1μs 10ms~100ms 99.999 300mV rms 0.01 +0.02 750V 10μs 100ms~200ms 199.99 0.05 +0.02 200mV rms Maximum Crest factor: 3.0 at full scale Maximum input voltage: 750Vrms...

  • Page 71: Chapter 8 Program Examples

    Chapter 8 Program Examples Serial Interface Program The following example is a communication program. It is programmed with C Language and working in DOS environment. Where the MAIN Function could be extended for communication functions by users and other sub functions show you how to input and output character strings using serial interfaces. #define PORT 0 #include "dos.h"...
  • Page 72 { c = 0; for( m = 100;m;m-- ) { send_port( PORT,*ps ); for( n = 1000;n;n-- ) { delay(2); /* wait about 2ms,can use dos.h libray funtion:delay */ if( kbhit() && ( getch() == 27 ) ) /* if escape key keypress */ { printf( "\nE20:Serial Port Write Canceled!"...
  • Page 73 /* send a character to serial port */ void send_port( int port,char c ) { union REGS r; r.x.dx = port; /* serial port */ r.h.ah = 1; /* int14 function1: send character */ r.h.al = c; /* character to be sent */ int86( 0x14,&r,&r );...

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