B&K Precision MDL4U400, MDL4U305, MDL4U302, MDL4U200,MDL4U252,MDL4U302,MDL4U305,MDL4U400,MDL4U505,MDL4U600, MDL4U200 User manual

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Safety Summary

The following safety precautions apply to both operating and maintenance personnel and must be followed during all
phases of operation, service, and repair of this instrument.

Before applying power to this instrument:

• Read and understand the safety and operational information in this manual.

• Apply all the listed safety precautions.

• Verify that the voltage selector at the line power cord input is set to the correct line voltage. Operating the instrument
at an incorrect line voltage will void the warranty.

• Make all connections to the instrument before applying power.

• Do not operate the instrument in ways not specied by this manual or by B&K Precision.

Failure to comply with these precautions or with warnings elsewhere in this manual violates the safety standards of design,
manufacture, and intended use of the instrument. B&K Precision assumes no liability for a customer’s failure to comply
with these requirements.

2

Category rating

The IEC 61010 standard denes safety category ratings that specify the amount of electrical energy available and the
voltage impulses that may occur on electrical conductors associated with these category ratings. The category rating is
a Roman numeral of I, II, III, or IV. This rating is also accompanied by a maximum voltage of the circuit to be tested,
which denes the voltage impulses expected and required insulation clearances. These categories are:

Category I (CAT I): Measurement instruments whose measurement inputs are not intended to be connected to the

mains supply. The voltages in the environment are typically derived from a limited-energy trans­former or a battery.

Category II (CAT II): Measurement instruments whose measurement inputs are meant to be connected to the mains

supply at a standard wall outlet or similar sources. Example measurement environments are portable
tools and household appliances.

Category III (CAT III): Measurement instruments whose measurement inputs are meant to be connected to the mains

installation of a building. Examples are measurements inside a building’s circuit breaker panel
or the wiring of permanently-installed motors.

Category IV (CAT IV): Measurement instruments whose measurement inputs are meant to be connected to the primary

power entering a building or other outdoor wiring.

Do not use this instrument in an electrical environment with a higher category rating than what is specied in this manual
for this instrument.

You must ensure that each accessory you use with this instrument has a category rating equal to or higher than the
instrument’s category rating to maintain the instrument’s category rating. Failure to do so will lower the category rating
of the measuring system.

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Electrical Power

This instrument is intended to be powered from a CATEGORY II mains power environment. The mains power should be
115 V RMS or 230 V RMS. Use only the power cord supplied with the instrument and ensure it is appropriate for your
country of use.

Ground the Instrument

To minimize shock hazard, the instrument chassis and cabinet must be connected to an electrical safety ground. This
instrument is grounded through the ground conductor of the supplied, three-conductor AC line power cable. The power
cable must be plugged into an approved three-conductor electrical outlet. The power jack and mating plug of the power
cable meet IEC safety standards.

Do not alter or defeat the ground connection. Without the safety ground connection, all accessible conductive parts
(including control knobs) may provide an electric shock. Failure to use a properly-grounded approved outlet and the
recommended three-conductor AC line power cable may result in injury or death.

3

Unless otherwise stated, a ground connection on the instrument’s front or rear panel is for a reference of potential only
and is not to be used as a safety ground. Do not operate in an explosive or ammable atmosphere.

Do not operate the instrument in the presence of ammable gases or vapors, fumes, or nely-divided particulates.

The instrument is designed to be used in oce-type indoor environments. Do not operate the instrument

• In the presence of noxious, corrosive, or ammable fumes, gases, vapors, chemicals, or nely-divided particulates.

• In relative humidity conditions outside the instrument’s specications.

• In environments where there is a danger of any liquid being spilled on the instrument or where any liquid can condense
on the instrument.

• In air temperatures exceeding the specied operating temperatures.

• In atmospheric pressures outside the specied altitude limits or where the surrounding gas is not air.

• In environments with restricted cooling air ow, even if the air temperatures are within specications.

• In direct sunlight.

This instrument is intended to be used in an indoor pollution degree 2 environment. The operating temperature range is
0∘C to 40∘C and 20% to 80% relative humidity, with no condensation allowed. Measurements made by this instrument
may be outside specications if the instrument is used in non-oce-type environments. Such environments may include
rapid temperature or humidity changes, sunlight, vibration and/or mechanical shocks, acoustic noise, electrical noise,
strong electric elds, or strong magnetic elds.

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Do not operate instrument if damaged

If the instrument is damaged, appears to be damaged, or if any liquid, chemical, or other material gets on or inside the
instrument, remove the instrument’s power cord, remove the instrument from service, label it as not to be operated,
and return the instrument to B&K Precision for repair. Notify B&K Precision of the nature of any contamination of the
instrument.

Clean the instrument only as instructed

Do not clean the instrument, its switches, or its terminals with contact cleaners, abrasives, lubricants, solvents, acids/bases,
or other such chemicals. Clean the instrument only with a clean dry lint-free cloth or as instructed in this manual. Not
for critical applications

This instrument is not authorized for use in contact with the human body or for use as a component in a life-support
device or system.

4

Do not touch live circuits

Instrument covers must not be removed by operating personnel. Component replacement and internal adjustments must
be made by qualied service-trained maintenance personnel who are aware of the hazards involved when the instrument’s
covers and shields are removed. Under certain conditions, even with the power cord removed, dangerous voltages may
exist when the covers are removed. To avoid injuries, always disconnect the power cord from the instrument, disconnect
all other connections (for example, test leads, computer interface cables, etc.), discharge all circuits, and verify there
are no hazardous voltages present on any conductors by measurements with a properly-operating voltage-sensing device
before touching any internal parts. Verify the voltage-sensing device is working properly before and after making the
measurements by testing with known-operating voltage sources and test for both DC and AC voltages. Do not attempt
any service or adjustment unless another person capable of rendering rst aid and resuscitation is present.

Do not insert any object into an instrument’s ventilation openings or other openings.

Hazardous voltages may be present in unexpected locations in circuitry being tested when a fault condition in the circuit
exists.

Fuse replacement must be done by qualied service-trained maintenance personnel who are aware of the instrument’s fuse
requirements and safe replacement procedures. Disconnect the instrument from the power line before replacing fuses.
Replace fuses only with new fuses of the fuse types, voltage ratings, and current ratings specied in this manual or on
the back of the instrument. Failure to do so may damage the instrument, lead to a safety hazard, or cause a re. Failure
to use the specied fuses will void the warranty.

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Servicing

Do not substitute parts that are not approved by B&K Precision or modify this instrument. Return the instrument to
B&K Precision for service and repair to ensure that safety and performance features are maintained.

For continued safe use of the instrument

• Do not place heavy objects on the instrument.

• Do not obstruct cooling air ow to the instrument.

• Do not place a hot soldering iron on the instrument.

• Do not pull the instrument with the power cord, connected probe, or connected test lead.

• Do not move the instrument when a probe is connected to a circuit being tested.

Compliance Statements

5

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
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.

123

2. Connection of the instrument to a test object may produce radiations beyond the specied 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

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Waste Electrical and Electronic Equipment (WEEE) Directive

Disposal of Old Electrical & Electronic Equipment (Applicable in the European Union and other European
countries with separate collection systems)

This product is subject to Directive 2002/96/EC of the European Parliament
and the Council of the European Union on waste electrical and electronic equipment
(WEEE), and in jurisdictions adopting that Directive, is marked as being put on the
market after August 13, 2005, and should not be disposed of as unsorted municipal
waste. Please utilize your local WEEE collection facilities in the disposition of this
product and otherwise observe all applicable requirements.

Safety Symbols

6

Symbol Description

indicates a hazardous situation which, if not avoided, will result in death or serious injury.

indicates a hazardous situation which, if not avoided, could result in death or serious injury

indicates a hazardous situation which, if not avoided, will result in minor or moderate injury

Refer to the text near the symbol.

Electric Shock hazard

Alternating current (AC)

Chassis ground

Earth ground

This is the In position of the power switch when instrument is ON.

This is the Out position of the power switch when instrument is OFF.

is used to address practices not related to physical injury.

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Contents

1 Introduction 9

1.1 Product Overview 9

1.2 Description 9

1.3 Features 10

1.4 Dimensions 10

1.5 Front Panel 11

1.6 Rear Panel 12

1.7 Protection Functions 13

1.7.1 Overvoltage Protection (OVP) 13

1.7.2 Operations to Clear the OVP State 13

1.7.3 Overcurrent Protection (OCP) 13

1.7.4 Overpower Protection (OPP) 14

1.7.5 Overtemperature Protection (OTP) 14

1.7.6 Reverse Voltage Protection (LRV/RRV) 15

1.8 Menu List 15

2 Installation 19

2.1 Inspection 19

2.2 Cleaning 19

2.3 Installing Modules 19

2.4 Channel Number 22

2.5 Location 23

2.6 Input Voltage Selection 23

2.7 Turn-On Checkout 24

2.8 If the Electronic Load Does Not Turn On. 24

3 Load Connection 26

3.1 Parallel Connection 27

3.2 Mainframe 8-pin Control Connector 28

3.3 External Trigger Connections 29

3.3.1 Trigger Modes 29

3.4 External ON/OFF Control Connection 30

3.5 Mainframe Extension Connection 30

3.6 PC Control Connection 31

4 Operations 32

4.1 Operation Modes 32

4.1.1 Constant Current (CC) Mode 32

4.1.2 Constant Voltage (CV) Mode 34

4.1.3 Constant Resistance (CR) Mode 35

4.1.4 Constant Power (CP) Mode 36

4.1.5 Constant Impedance (CZ) Mode 37

4.1.5.1 Setting CV,CC,CR, CW,CZ Mode 38

4.2 Local Operations 39

4.2.1 Mainframe Panel 39

4.2.2 Module Panel 41

4.2.3 Module Panel Lock 42

4.3 Switching Channels 42

4.4 Channel Synchronization 42

4.5 Module VFD Indicator Function Description 43

4.6 Transient Operation 44

4.6.1 Continuous 44

4.6.2 Pulse 45

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4.6.3 Toggle 45

4.6.4 Setting Up A/B Transient Operation 46

4.7 List Operation 48

4.7.1 Setting Up List Operation Mode 48

4.8 Trigger Operation 51

4.8.1 Manual Trigger 51

4.8.2 External Trigger Signal(TTL level) 51

4.8.3 Hold Trigger 51

4.8.4 Bust Trigger 51

4.8.5 Timer Trigger 51

4.9 Short Operation 51

4.10 Input On/O Operation 51

4.11 Von Operation 52

4.12 Save and Recall Operation 54

4.13 Module Controlling Link 54

4.13.1 Voltage Failure Indication 55

4.13.2 Current Monitoring 55

4.13.3 Digital I/O 55

4.13.4 Remote Sense Function 55

4.13.5 External Analog Control 55

4.14 Automatic Test 56

4.15 Conguring Pass/Fail Paramters 56

4.15.1 Conguring Instrument Settings 56

4.15.2 Recall Test Files 59

4.16 Remote Operation 60

4.16.1 USB Interface 61

4.16.2 Ethernet Interface 61

4.16.3 GPIB Interface 61

8

5 Specications 64

6 Service Information 66

7 LIMITED THREE-YEAR WARRANTY 67

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Introduction

1.1 Product Overview

This section describes the main features and menus of the MDL4U Series DC Electronic Load. The MDL4U Series is
comprised of two parts, mainframes and modules. The mainframes mentioned are the MDL4U001 mainframe and the
MDL4U002 mainframe extension. Modules in this series include the MDL4U200, MDL4U252, MDL4U302, MDL4U305,
MDL4U400, MDL4U505, and MDL4U600. Unless otherwise noted, this document will refer to all of these instruments as
“electronic load”. The range of each module’s specic voltage, current, and power is listed in the Specications section.

1.2 Description

Front View Rear View

Figure 1.1 MDL4U 001 and 002 Populated

The MDL4U Series is a multi-channel modular programmable electronic load system. Seven dierent modules of pro­grammable DC loads ranging in power from 200 W to 600 W provide users the exibility to test a wide range of power
sources from multi-output DC power supplies to batteries, fuel cells, and photovoltaic arrays.

Up to four modules can be installed into the MDL4U001 mainframe to support up to a total of 8 channels. Adding the
MDL4U002 mainframe extension will enable the system to support four additional module slots for a maximum of 16
channels. The electronic load is congured by installing user-selectable modules into the mainframe and operated using
the front panel keypad and rotary knob. It can also be controlled remotely via USB, RS-232, LAN, or GPIB interface.
The electronic load modules all have similar functions, but may dier in range of input voltage, current, and power. The
high resolution voltage and current measurement system provides both accuracy and convenience.

The electronic load can be used in one of ve dierent operation modes: constant voltage (CV), constant current (CC),
constant resistance (CR), constant power (CW), or constant impedance (CZ). All panel operation and programming
functions are carried out on the MDL4U001 mainframe panel. A wide range of dynamic loading applications can be
simulated through user-programmable slew rates, load levels, duration, and conducting voltage.

Model MDL4U200 MDL4U252 MDL4U302 MDL4U305 MDL4U400 MDL4U505 MDL4U600

Power 200 W *250 W/50W *300 W/300 W 300 W 400 W 500 W 600 W

Operating Voltage 80 V 80 V 80 V 500 V 80 V 500 V 80 V

Rated Current 40 A 20 A 45 A 20 A 60 A 30 A 120 A

No. of Channels 1 2 2 1 1 1 1

Table 1.1 MDL4U Modules

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Introduction 10

* The MDL4U252 and MDL4U302 are dual-channel load modules. The MDL4U252 can allocate up to 250 W to either
channel up to 300 W total. (e.g. 250 W/50 W, 150 W/150 W). Similarly, the MDL4U302 can allocate 300 W to either
channel up to 600 W total (e.g. 300 W/300 W)

1.3 Features

• Power range up to 2400 W

• Voltage range up to 500 V

• Current range up to 120 A

• CC/CV/CR/CW/CZ operating modes

• Removable modules for easy system congurability

• Support for up to 16 channels using dual channel modules with mainframe extension

• Operate identical modules in parallel mode for high current applications

• Synchronous load on/o function

• Standard LAN, GPIB, USB, and RS232 interfaces with USBTMC/SCPI protocol support

• Analog current control and monitoring

• Transient mode up to 25 kHz

• List mode (sequence mode) - minimum 20 s step width with 84 user programmable steps

• Adjustable slew rate in CC mode

• 16-bit voltage and current measurement system providing high resolution of 0.1 mV and 0.01 mA

• Automatic test function

• 101 memory locations to save/recall setting parameters

• Remote sense

• OVP/OCP/OPP/OTP and reverse voltage protection

• Rack-mount brackets with handles included

1.4 Dimensions

The MDL4U’s dimensions are as follow:

MDL4U Model : 001 002 200, 252, 302, 305, 400, 505, 600

Type Mainframe Mainframe extendsion Module

Dimensions

(W x H x D)

Weight 34 lbs (15.4 kg) 34 lbs (15.4 kg) 11 lbs (5 kg)

17.3” x 7” x 21.6”

(440 x 177.3 x 549 mm)

17.3” x 7” x 21.6”

(440 x 177.3 x 549 mm)

3.2” x 6.7” x 22.6”

(82 x 170.5 x 573 mm)

Table 1.2 MDL4U Modules

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Introduction 11

1.5 Front Panel

Figure 1.2 Front Panel

Item Name Description

1 VFD Display Displays electronic load information.

2 Module Panel Keys Controls module functions. Refer to Module section for more details.

3 Rotary Knob Used to change parameters.

4 Mainframe Function Keys Controls each channel’s operating status. Refer to Mainframe for more details.

5 Mainframe Numeric Keypad Used to enter precise values when adjusting parameters.

6 Power Switch Turns the system ON or OFF.

7 Mainframe Index Channel index indicating the corresponding slot’s channels.

8 Modules Select and add any combination of 4 modules including dual-channel modules .

9 Rack-Mount Ear Ears that protrude out on each side to be fastened to the frame with screws.

Table 1.3 Front Panel

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Introduction 12

1.6 Rear Panel

Figure 1.3 Rear Panel

Item Name Description

1 GPIB Interface Connect a GPIB cable to remotely control the unit

2 Module Input Terminal Load input termianls.

3 Current Monitoring Connect an external voltmeter or oscilloscope to display the input’s current.

4 Remote Sense/External Control

5 Digital I/O and VF Output

6 Extended Mainframe Connects MDL4U001 to MDL4U002 to expand channel capacity to 16 channels.

7

8 USB Interface Connect a USB type B to type A to remotely control the unit.

9 Line Voltage Selection Select 110/220V±10%AC input.

10

11 LAN Interface

12 RS232 Interface Connect a cable with a two COM interface (DB9) to remotely control the unit.

AC Power Input

& Fuse Box

Trigger I/O &

Load On/O Terminals

Remote Sense:Eliminates the eect of voltage drop in the load leads.
External Control Contol the module using an external analog source.

Digital I/O: Universal output terminal use to control an external instrumnet.
VF Output: Voltage fault indication terminal.

Houses the fuse and the AC input.

Refer to section 8-pin Control Connector for more details.

Connect a Cat 5/6 Ethernet straight-through patch cable to remotely control
the unit.

13 Not Used For factory use only.

Table 1.4 Rear Panel

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Introduction 13

1.7 Protection Functions

The electronic load has the following protection functions: Overvoltage protection (OVP), overcurrent protection (OCP),
overpower protection (OPP), overtemperature protection (OTP), and local and remote reverse voltage protection (LRV/RRV).

The mainframe will act appropriately once any of the above protections are active. You can press any button on the front
panel to restore the protection function. For example, if the electronic load triggers the overtemperature protection, the
buzzer will alarm, the input will automatically turn o, and the mainframe VFD will display OTP.

1.7.1 Overvoltage Protection (OVP)

If the OVP circuit has triggered, input will turn o, buzzer alarm will go o, and the status register’s OV and VF bit will
be set. The mainframe will display OVP and the condition will remain until they are reset. Once overvoltage protection
occurs, the 8-pin connector’s VF pin on the rear panel will output TTL high voltage level. You can control the output
state of the power supply under test via this pin (see Figure 4.16).

1.7.2 Operations to Clear the OVP State

Check whether the input voltage is within the electronic load’s rated voltage or the programmed protection voltage ranges.
If it is outside the range, please disconnect the device under test. Then press any key on the front panel or remotely send
SCPI command PROTection:CLEar. The OVP displayed on the front panel will turn o and the electronic load exits
OVP protection state.

1.7.3 Overcurrent Protection (OCP)

The electronic load includes both hardware and software overcurrent protection features.

Hardware OCP - The electronic load’s maximum input current will be limited to approximately 110% of the current range.
Once the hardware OCP is triggered, the status register’s OC bit will be set. When the hardware OCP is removed, the
status register’s OC bit will be reset. Hardware overcurrent protection will not aect the electronic load’s on/o state.

To set the electronic load’s OCP value:

1. Power on the electronic load. Self-test

2. Press + to enter Conguration menu.

3. Press key to select PProtect and press Enter to go into protection menu.

4. Press key to select Alimit State and press Enter.

– Select On and press Enter to conrm.

5. Press key to select Alimit Point and press Enter.

– Input OCP current value and press Enter to conrm.

6. Press key to select Alimit Delay and press Enter.

– Input delay time before alarm and press Enter to conrm.

7. Press Esc key to exit menus

If the electronic load’s current value is above the set overcurrent protection value, the electronic load will automatically
turn o and the VFD will display OCP. At the same time, the OC and PS bits in the status register will be set and remain
until they are reset.

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Introduction 14

Operations To Clear the OCP State

Check whether the input current is within the electronic load’s rated current or the programmed protection current ranges.
If it is outside the range, disconnect the device under test. Then press any key on the front panel or remotely send SCPI
command PROTection:CLEar. The OCP displayed on the front panel will turn o and the load exits OCP protection
state.

1.7.4 Overpower Protection (OPP)

The electronic load includes both hardware and software OPP features.

Hardware OPP – In the event that the electronic load’s input power exceeds the set power protection limit, the hardware
OPP will limit the power. Once the hardware OPP is triggered, the status register’s OP bit will be set. When the
hardware OPP is removed, the status register’s OP bit will be reset. Hardware overpower protection will not turn the
electronic load’s input o.
To set the electronic load’s OPP value:

1. Power on the electronic load. Self-test

2. Press + to enter Conguration menu.

3. Press key to select PProtect and press Enter to go into protection menu.

4. Press key to select Plimit Point and press Enter.

– Input OPP power value and press Enter to conrm.

5. Press key to select Plimit Delay and press Enter.

– Input delay time before alarm and press Enter to conrm.

6. Press Esc key to exit menus

If the electronic load’s power value is above the set overpower protection value, the electronic load will automatically turn
o and the VFD will display OPP. At the same time, the OP and PS bits in the status register will be set and remain
until they are reset.

Operations to Clear the OPP State

Check whether the input power is within the rated power range or the programmed protection ranges. If it is out­side the range, disconnect the device under test. Then press any key on the front panel or remotely send command
PROTection:CLEar. The OPP displayed on the front panel will turn o and the electronic load exits OPP protection
state.

1.7.5 Overtemperature Protection (OTP)

Each module has an overtemperature protection circuit, which will turn o the input if the internal temperature exceeds
safe limits. When the electronic load’s internal circuit temperature is over 85°C, the load will enable OTP. Input will
automatically be turned o and the VFD will display OTP. At the same time the OT and PS bits in the status register
will be set and remain until they are reset.

Operations to Clear the OTP State

When the electronic load temperature has dropped below the protection point, press any key on the front panel or
remotely send command PROTection:CLEar. The OTP displayed on the front panel will turn o and the electronic load
exits OTP protection state.

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Introduction 15

1.7.6 Reverse Voltage Protection (LRV/RRV)

This function protects the electronic load in case the input DC voltage lines are connected with the wrong polarity. When
a reverse voltage (LRV – local reverse voltage, RRV – remote reverse voltage) connection condition is detected, the input
will immediately turn o, the buzzer will alarm the user, and the status register’s reverse voltage (LRV/RRV) and VF
bits will be set. The mainframe will display LRV/RRV until they are reset.

In this condition, the 8-pin connector’s VF pin will output a high level. You can disconnect the power supply via this
signal (see Figure 4.16).

Operations to Clear the Reverse Voltage State

Check whether the connection is reversed. If so, disconnect the device to be measured to clear the reverse voltage state.

1.8 Menu List

The following menus can be viewed on the VFD display. Use the keys to scroll through the menu list. Press the
Enter key to enter the selected menu function. Use the keys to scroll through the VFD screen and press Enter
key to enter its submenu. Press Esc to go back to the previous menu selection. Pressing number keys can directly select
a channel.

Press the the key to enter the Setup menu.

Setup

MODE Select working mode

CONST CURRENT Load works in CC mode

CONST VOLTAGE Load works in CV mode

CONST RESISTANCE Load works in CR mode

CONST POWER Load works in CW mode

CONST IMPEDANCE Load works in CZ mode

CC/CV RANGE Switch the range

HIGH RANGE Set high range

LOW RANGE Set low range

I / V / R / W SET Set the working current/voltage/resistance/power value

Vmax/Amax Set up the maximum voltage/current limit for Automatic test mode

Vmin/Amin Set up the minimum voltage/current limit for Automatic test mode

∫ = 2.500A/us Set the rising slew rate (only in CC mode)
∫ = 2.500A/us Set the falling slew rate (only in CC mode)

TRAN A = 0.00A Set up level A value

Ta = 0.0005S Set up level A width

TRAN B = 0.00A Set up level B value

Tb = 0.0005S Set up level B width

T MODE Set up the transient mode

CONTINUOUS Continuous

PULSE Pulse mode

TOGGLE Toggle mode

RLC R = 7500.0Ω Set up the resistance value

RLC L = 0uH Set up the inductance value

RLC C = 10uF Set up the capacitance value

EXIT Exit the setup menu

Table 1.5 Setup Menu

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Introduction 16

System Menu

Press + to enter the System menu.

MENU

INITIALIZE

INITIALIZE

DEFAULT SET

POWER ON SET

RST (DEFAULT) Set the load’s input state to default at power on

SAV0 Set the load’s input state to SAV0 at power on

BUZZER SET Set up the buzzer state

ON Enable the function

OFF (DEFAULT) Disable the function

LOAD ON KNOB Module knob mode setting

UPDATE (DEF) Real-time update

OLD

TRIGGER SOUR. Set up the trigger mode

MANUAL (DEF) Manual trigger

EXTERNAL External signal trigger mode

HOLD Hold trigger mode

BUS Bus trigger mode

TIMER Timer trigger

TRIGGER TIMER Trigger timer setting

TRIGGER TIMER SET Set the time of the trigger timer

COMMUNICATION Select the interface for remote communication

RS232 (DEF)

USBTMC-USB488

GPIB

ETHERNET

RS232 SET

BAUDRATE SET Set up the communication baud rate

PARITY SET Set up the communication parity

HANDSHAKE SET Select the handshake protocol

Resume all conguration to default settings

No update (when turning load ON/OFF, original value before
use of rotary knob will be set)

4800 (DEFAULT)

9600
19200
38400
57600

115200

NONE (DEFAULT)

ODD

EVEN

NONE (DEFAULT)

CTS/RTS

XON/XOFF

Table 1.6 System Menu

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Introduction 17

System Menu Cont...

GPIB ADDRESS GPIB address setting

GPIB ADDRESS SET Set up communication address

ETHERNET SET Ethernet settings

GATEWAY SET Gateway setting

IP SET IP setting

MASK SET Mask setting

PORT SET Port setting

EXIT

EXPAND MODULE Module expansion

ON Enable the function

OFF (DEFAULT) Disable the function

LANGUAGE SET Communication protocol

SCPI (DEFAULT) SCPI protocol
EXTEND TABLE Expand SCPI protocol, compatible with others

ABOUT Mainframe production information

MDL### Mainframe production model number

SN: ########## Mainframe production serial number

VER: 1.43 Mainframe software version

EXIT

Table 1.7 System Menu Cont...

Conguration Menu

Press + to enter the Conguration menu.

Conguration Menu

SYNC ON SET Setup Synchronization ON / OFF function

ON (DEFAULT) Turn on synchronization function

OFF Turn o synchronization function

VON

VON POINT Set the load’s Von point

VON LATCH Von latch state

ON (DEFAULT) Turn on Von latch

OFF Turn o Von latch

EXIT Exit the menu

AVERAGE COUNT Average count setting 2^X (adjustable from 2^2 to 2^16)

V AUTORANGE Auto switching voltage range

ON (DEFAULT) Enable this function

OFF Disable this function

Table 1.8 Conguration Menu

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Introduction 18

Conguration Menu Cont...

ALIMIT POINT Set up software current protection value

ALIMIT DELAY Set up software current protection delay

PLIMIT POINT Set up software power protection value
PLIMIT DELAY Set up software power protection delay

ON TIMER STATE Set up LOAD ON timer state

ON TIMER SET Set up LOAD ON timer time

EXIT Exit the menu

LIST

FUNCTION MODE Select mode

FIXED Choose xed operation mode

LIST Choose list operation mode

RECALL LIST Recall list operation le

EDIT LIST Edit list operation le

HIGH RANGE Edit high range of list operation

LOW RANGE Edit low range of list operation

EXT. CTRL SET External analog control function

ON Turn on external analog control function

OFF (DEFAULT) Turn o external analog control function

REM SENSE SET Remote sense function

ON Enable remote sense function

OFF (DEFAULT) Disable remote sense function

ABOUT Module production information

MDL### Channel production model

SN:######## Channel production serial number

VER: 1.35 Channel software version

EXIT Exit the menu

Table 1.9 Conguration Menu Cont...

Automatic Test Menu

Press + to enter the Automatic Test menu.

Automatic Test Menu

PROGRAM

RUN PROGRAM Run the testing le

RECALL PROG Recall the testing le

EDIT PROGRAM Edit the testing le

EXIT

Table 1.10 Automatic Test Menu

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Installation

2.1 Inspection

This instrument was carefully inspected before shipment. Upon receipt, inspect the instrument for damage that might
have occurred during transit. If any sign of damage is found, please notify your B&K Precision distributor.

The following standard and optional accessories are provided with each mainframe or module.

Mainframes include:

• Power cord

• USB cable (MDL4U001 only)

• Mainframe extension cable accessory (MDL4U002 only)

Modules include:

• Certicate of calibration

Note:

Ensure the presence of all the items above. Notify your B&K Precision distributor if anything is missing.

2.2 Cleaning

Use a dry cloth or one slightly dampened with water to clean the external case parts. Do not attempt to clean internally.

Warning:

To prevent electric shock, please unplug the power cord connected to the unit before cleaning.

2.3 Installing Modules

Caution:

Static electricity may damage load modules. Please install modules according to
standard electrostatic prevention. Avoid touching joints and circuit boards.

Any combination of modules up to 2400 W total in the MDL4U001 mainframe in any order. This also applies to the
MDL4U002 mainframe extension, allowing a maximum of 4800 W total when connecting the MDL4U001 and MDL4U002
together. The procedure of installing modules to the mainframe extension is the same as that of the MDL4U001
mainframe.

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Installation 20

Installation Procedure

1. Turn the mainframe o and disconnect the power cord.

2. Remove the plastic cover with a at-blade screwdriver.

Figure 2.1 Removing Covers

3. Loosen the screws on the rear panel and remove the metal place holders.

Figure 2.2 Removing Rear Cover Screws

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Installation 21

4. Insert and slide the selected modules into the slot.

Figure 2.3 Module Installation

5. Insert and tighten module screws on rear panel.

Figure 2.4 Tighten Module Rear Screws

6. Install more modules in other slots following the same process (stes 2 through 5).

7. Reconnect the power cord.

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Installation 22

2.4 Channel Number

The channel number for all modules is determined by the location of the modules in relation to the mainframe and
ordered from right to left. With the MDL4U001 mainframe, the total number of channels is 8. Channels 1 and 2 are next
to the mainframe front panel, while channels 7 and 8 are located on the left side. Load channel number is xed even if
the location is unoccupied. Dualchannel modules such as the MDL4U252 and MDL4U302 have two channels. If it is a
single-channel module, the channel number is automatically assigned the rst number of the slot. Figure 2.5 shows the
default channel number order.

Figure 2.5 Channel Number

Figure 2.6 shows an examples of how channels are assigned when single-channel modules are installed.

Figure 2.6 Single Channel Modules Numbering

Figure 2.7 shows an examples of how channels are assigned when single-channel modules and dualchannel modules are
installed are installed.

Figure 2.7 Single and Dual Channel Modules Numbering

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Installation 23

2.5 Location

The operating temperature of the MDL4U Series DC Electronic Load is 0 to 40 ℃. A fan cools the electronic load by
drawing air through both the top and front, and then exhausting it out the back. Therefore, the electronic load must be
installed in a location that allows sucient space on the front and back of the unit for adequate air circulation.

Minimum clearances for bench operation are 2 inches from the top and 3 inches from the front and back. If there are
radiator fans in your cabinet, please avoid installing the load near the fan, since it may limit air circulation of the load.
If you are installing equipment on top of your electronic load in the cabinet, use a ller panel above the unit to ensure
adequate air circulation.

Caution:

Do not block the fan exhaust at the rear of the load. When the load is used on a
bench, make sure there is enough space on the front and rear of the equipment for air
circulation.

2.6 Input Voltage Selection

The electronic load can work under 110/220V±10% AC input, identied by an input line voltage switch on the rear (refer
to Figure 2.8). If the indicated line voltage does not match your region, please use the switch in the back of the unit to
choose your input line voltage, install appropriate fuse (refer to Table 2.2 below), and then insert power cord.

Caution:

Check to make sure correct fuse is installed when line voltage is switched.

Figure 2.8 Input Voltage Selection

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Installation 24

2.7 Turn-On Checkout

When you turn on the electronic load, the front-panel display will light up briey while the electronic load performs its
power-on self-test. The following table shows the procedure of the self-test.

Mainframe VFD Display Description

BIOS Ver 1.20 VFD displays software version

SYSTEM SELF TEST System self-check

CH1/2/3/4/5/6/7/8

SCAN...

.7.5.3.1

Detecting all installed modules

e.g.CH01 CV OFF

Vdc=0.0000V Adc=0.0000A

Wdc= 0.00W

Warning:

Your electronic load is equipped with a 3-wire grounding type power cord; the third conductor being
ground. The electronic load is grounded only when the power-line cord is plugged into an appropriate
receptacle. Do not operate your power supply without adequate cabinet ground connection.

Displays information of channel 1 or the leftmost channel. Use up and
down key to select other channels.

Table 2.1 Turn-On Procedure

2.8 If the Electronic Load Does Not Turn On.

Use the following troubleshooting steps to help solve problems you might encounter when turning on the instrument:

1. Verify that there is AC power to the electroic load.
First, verify that the power cord is rmly plugged into the power receptacle on the rear panel of the electronic load.
You should also make sure the power source you plugged the electronic load into is energized. Then check to see
that the electronic load is turned on.

2. Verify the power line voltage setting.
The line voltage is set to the proper value for your country (110VAC or 220VAC) when the electronic load is shipped
from factory. Change the line voltage setting if it is not correct.

3. Verify that the correct power line fuse is installed and not burned out.
If fuse is blown, please replace it according to the following specication.

Product Fuse specication (110 VAC) Fuse Specication (220 VAC)

MDL4U001 T5A, 250 V T2.5A, 250 V
MDL4U002 T5A, 250V T2.5A, 250 V

Table 2.2 Fuse Specications

4. Replace fuse.
Use a at-bladed screwdriver to open the small plastic cover under the AC input connector on the rear panel of the
load and then replace with matching fuse.

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Installation 25

Figure 2.9 Fuse Location

Figure 2.10 Fuse Removal

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Load Connection

Warning:

To satisfy safety requirements, load wires between the electronic load and the device under test (DUT)
should have a current rating high enough not to overheat while carrying the short-circuit output current.
Never make connections between the electronic load and a DUT while the electronic load inputs are turned
ON and/or the DUT has live power at its output.

Before connecting the device to be measured to the electronic load, please remove the cover on the output terminals of
the load and cover it after completing the connection. Please pay attention to the type, length, and polarity when wiring.
Avoid using wires of minimum specication of heating, which are unable to supply good load regulation.

Generally speaking, if the wires are short enough, they can control a voltage drop of less than 0.5 V. In addition, bonding
them together can reduce induction and noise. Connect wire from positive terminal of module to positive terminal of
device. Similarly, connect the corresponding negative terminal. Figure 3.1 illustrates a typical connection of the module
with the device to be measured.

Figure 3.1 Module Input

There are two positive terminals and two negative terminals on the rear panel of every module. Single terminal connection
is adequate when the input current is less than 30 A.

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Load Connection 27

Warning:

Each terminal can carry up to 30 A current. Double-terminal connection is needed when the input current
is more than 30 A. Refer to Figure 3.1 - Connection of Load and Device Under Test (DUT) for double­terminal connection.

3.1 Parallel Connection

Parallel connection can be applied between modules of the same model to increase current and power dissipation, but it
cannot be applied between dierent modules.

Modules can be paralleled in CC, CR, or CW mode, but cannot be paralleled in CV or CZ mode.

Each module will dissipate the power it has been programmed at. For example, after being paralleled, two single-channel
modules rated at 80V/40A/300W can dissipate up to 80V/80A/600W.

Figure 3.2 illustrates the paralleled connection for increased power dissipation.

Figure 3.2 Parallel Module Connection

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Load Connection 28

3.2 Mainframe 8-pin Control Connector

The mainframe’s 8-pin control terminal on the rear panel is shown below. This is used for external trigger and ON/OFF
control connections.

Figure 3.3 Mainframe Rear Panel 8-pin Control Connnector

Pin Signal Description

1 Trigger IN Trigger Signal Input
2 Trigger OUT Trigger Signal Output
3 ON/OFF IN Synchronization ON/OFF Control Signal Input
4 ON/OFF OUT Synchronization ON/OFF Signal Output
5 NC No Connection
6 NC No Connection
7 GND Ground
8 GND Ground

Table 3.1 Control Connector Pinout

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Load Connection 29

3.3 External Trigger Connections

There is ve kinds of trigger modes.To set the trigger mode:

1. Press the ( + ) to enter the System menu.

2. Press the navigation keys to select Trigger Source.

3. Press the navigation keys to select the desired trigger mode.

3.3.1 Trigger Modes

Manual Trigger Mode

To use the front panel trigger mode, set the trigger source to MANUAL.

Once trigger mode is set to manual press the

External Trigger Mode

To use rear panel trigger mode, set the trigger source to EXTERNAL. Inputting a TTL level pulse (>10 us) to the
trigger signal input (pin 1) of mainframe’s Mainframe 8-pin Control Connector on the rear panel will enable a trigger
operation. Figure 3.4 shows one way to produce a trigger signal.

Figure 3.4 Contact

with a TTL Pulse Source

When making contact with a TTL pulse source, it produces a trigger to change the setting value (voltage, current,
resistance, etc.), e.g. switch in transient mode, or create a pulse in dynamic pulse mode. At the same time, it will output
a trigger signal on pin 2.

Hold Trigger Mode

To use hold trigger mode, set trigger source to HOLD. Then send the TRIG:IMM command to trigger the electronic
load. Pin 2 of 8-pin Control Connector on the rear will also output a corresponding trigger signal when the electronic
load receives the TRIG:IMM command.

Bus Trigger Mode

To use BUS trigger mode, set the trigger source to BUS. Connect the electronic load by GPIB, USB, or Ethernet
communication interface.

When the TRIG command is received, the load will produce a trigger signal.

Timer Trigger Mode

To use timer trigger mode, set the trigger source to TIMER. Set the TRIGGER TIMER’s time, and the electronic load
will trigger at specied trigger timer setting and also produce a trigger signal on rear Trigger Out pin.

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Load Connection 30

3.4 External ON/OFF Control Connection

ON/OFF IN (pin 3 of rear 8-pin Control Connector) is used to toggle the multi-channel electronic load inputs ON or
OFF. When ON/OFF IN pin receives a TTL level pulse (>10us), the ON/OFF state of the load will toggle. SYNC ON
SET function can be set to ON for multiple channels to toggle more than one channel at a time.

ON/OFF OUT (pin 4 of rear 8-pin Control Connector) indicates ON/OFF state of the multi-channel electronic load. If
SYNC ON SET function of any specic channel is set to ON and the channel’s input state is ON, pin 4 outputs a low
TTL level signal. If the input state is o, pin 4 outputs a high TTL level signal.

3.5 Mainframe Extension Connection

Figure 3.5 Mainframe Extension Connection

The Extended Mainframe interface is used to connect the mainframe extension to expand the number of channels. Up
to 16 total channels can be supported when mainframe is connected to the mainframe extension.
Procedure:

1. Use expansion cable to connect the mainframe extension interface between the mainframe and mainframe extension.

2. Press + to enter System menu.

3. Use the keys to navigate through menu.

4. Select Expand Module and choose ON to enable expand function.

5. Press Enter to conrm.

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Load Connection 31

3.6 PC Control Connection

The MDL4U Series DC Electronic Load can achieve remote control via USB, RS-232, LAN, or GPIB interface, but only
one interface can be used at a time.
To choose the interface:

1. Connect communication cable before powering on.

– Do not hot plug, as it may damage the communication interface of the electronic load.

2. Power on the electronic load.

3. Select the channel number via keys.

4. Press the + to enter the System menu.

5. Select Communication and select the desired interface.

– Press Enter to conrm.

6. The display will return to the main menu.

Note:

When using RS232, GPIB, or LAN the commuincation settings must be set. To do so select RS232 Set,
GPIB Address, or Ethernet Set from the system menu.

See the Menu List for full listing of menus and submenus applicable to all other remote interfaces.

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Operations

4.1 Operation Modes

The electronic load has the following operation modes:

1. Constant Current (CC) Mode

2. Constant Voltage (CV) Mode (CV) Mode

3. Constant Resistance (CR) Mode

4. Constant Power (CW) Mode

5. Constant Impedance (CZ) Mode

4.1.1 Constant Current (CC) Mode

In CC mode the electronic load will sink a current in accordance with the programmed value regardless of the input
voltage.

Figure 4.1 Constanct Current Mode

CC Ranges

When working in CC mode, you can Press the the key to enter the RANGE menu. Two overlapping ranges can be
selected: LOW RANGE or HIGH RANGE. Current can be edited in either of the two ranges.

Low range will supply higher accuracy and better resolution when you set lower current. If any value you set is outside
the maximum value of the LOW RANGE, you should select HIGH RANGE. If the electronic load is in remote control
mode, you can use the CURR:RANG command to switch current range.

CC Vmax/Vmin Limits

The Vmax and Vmin parameters refer to the voltage high and low limit for the automatic test mode. During automatic
test mode, the device test under test (DUT) must be operating within the congured values for the test to PASS upon
completion. If the DUT operates outside the congured values, the test will FAIL upon completion.

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Operations 33

Note:

These parameters are used for Automatic Test ONLY.

Immediate Current Value

Set the current level via front panel or by sending SCPI command CURR n. If the load is in CC mode, the new current
level setting immediately changes the input at a rate determined by the slew rate. If the load is not in CC mode, the
current level setting will be saved for use until mode is switched to CC mode.

Transient Current Level

A/B transient current level can be set on the front panel or by remote operation. The load can continuously toggle
between the two levels when transient operation is turned on.

Set Slew Rate

The current slew rate determines the rate at which the input current to a module changes to a new programmed value.
You can set the current level’s rise/fall slew rate on the front panel or by remote operation. The programmed slew rate
is immediately in eect to the triggered and transient current level changes.

Slew Rate Measurement and Actual Transition Time

Current slew rate is dened as the change in current over time. A programmable slew rate allows a controlled transition
from one load setting to another. The actual transition time is dened as the time for the input to change from 10% to
90%, or 90% to 10% of the programmed current values. The graph below illustrates slew rate measurements.

Figure 4.2 Slew Rate Measurement

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Operations 34

Between the 10% and 90% region, the slew rate can be measured by observing the steepest slope portion. In case of very
large load changes, e.g. from no load to full load, the actual transition time will be larger than the expected (measured)
time. For this reason, the rmware allows the user to program slew rate values outside of the specied slew rate ranges.
The minimum transition time for all programmable slew rates is also limited in cases where the transition from one setting
to another is very small, due to bandwidth limitations of the load.

4.1.2 Constant Voltage (CV) Mode

In CV mode, the electronic load will attempt to sink enough current to cnotrol the source voltage to the programmed
value.

Figure 4.3 Constanct Voltage Mode

CV Ranges

When working in CV mode, you can Press the the key to enter the RANGE menu. Two overlapping ranges can be
selected: LOW RANGE or HIGH RANGE. Voltage can be edited in either of the two ranges.

Low range will supply higher accuracy and better resolution when you set lower current. If any value you set is outside
the maximum value of the LOW RANGE, you should select HIGH RANGE. If the electronic load is in remote control
mode, you can use the VOLT:RANG command to switch voltage range.

Amax/Amin Limits

These parameters refer to the current high and low limit for the automatic test mode. During automatic test mode, the
device under test (DUT) must be operating within the congured values for the test to PASS upon completion. If the
DUT operates outside the congured values, the test will FAIL upon completion.

Note:

These parameters are used for Automatic Test ONLY.

Voltage Level

Set the voltage level on front panel or by sending SCPI command VOLT n. If the load is in CV mode, the new setting
immediately changes the input. If the electronic load is not in CV mode, the set voltage level will be saved in the
instrument for use until the mode is switched to CV mode.

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Operations 35

Transient Voltage Level

A/B transient voltage level can be set on front panel or by remote operation. The electronic load can continuously toggle
between the two levels when transient operation is turned on.

4.1.3 Constant Resistance (CR) Mode

In CR mode, the electronic load is equivalent to a constant resistance, as shown in gure 4.4.
The electronic load will linearly change the current, according to the input voltage.

Figure 4.4 Constant Resistance Mode

CR Ranges

When working in CR mode, you can Press the the key to enter the RANGE menu. Two overlapping ranges can be
selected: LOW RANGE or HIGH RANGE. Resistance can be edited in either of the two ranges.

Low range will supply higher accuracy and better resolution when you set lower resistance. If any value you set is outside
the maximum value of the LOW RANGE, you should select HIGH RANGE. If the electronic load is in remote control
mode, you can use the RES:RANG command to switch resistance range.

CR Vmax/Vmin Limits

These parameters refer to the voltage high and low limit for the automatic test mode. During automatic test mode, the
device under test (DUT) must be operating within the congured values for the test to PASS upon completion. If the
DUT operates outside the congured values, the test will FAIL upon completion.

Note:

These parameters are used for Automatic Test ONLY.

Immediate Resistance Level

Set the resistance level via front panel or by sending SCPI command RES n. If the load is in CR mode, the new resistance
level setting immediately changes the input. If the load is not in CR mode, the resistance level setting will be saved for
use until mode is switched to CR mode.

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Operations 36

Transient Resistance Level

A/B transient resistance level can be set on front panel or by remote operation. The load can continuously toggle between
the two levels when transient operation is turned on.

4.1.4 Constant Power (CP) Mode

In CP mode, the electronic load will consume a constant power. When input voltage increases, the input current will
dexrease, while power (P = V * I) will remain the same.

Figure 4.5 Constant Power Mode

CP Ranges

When working in CW mode, you can Press the the key to enter the RANGE menu. Two overlapping ranges can
be selected: LOW RANGE or HIGH RANGE. Power can be edited in either of the two ranges.

Low range will supply higher accuracy and better resolution when you set lower power. If any value you set is outside the
maximum value of the LOW RANGE, you should select HIGH RANGE. If the electronic load is in remote control mode,
you can use the POW:RANG command to switch power range.

CP Vmax/Vmin Limits

These parameters refer to the voltage high and low limit for the automatic test mode. During automatic test mode, the
device under test (DUT) must be operating within the congured values for the test to PASS upon completion. If the
DUT operates outside the congured values, the test will FAIL upon completion.

Note:

These parameters are used for Automatic Test ONLY.

Immediate Power Level

Set the power level via the front panel. If the load is in CW mode, the new power level setting immediately changes the
input. If the load is not in CW mode, the power level setting will be saved for use until mode is switched to CW mode.

Transient Power Level

A/B transient power level can be set via the front panel or by remote operation. The electronic load can continuously
toggle between the two levels when transient operation is turned on.

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Operations 37

4.1.5 Constant Impedance (CZ) Mode

In CZ mode, the electronic load uses an A/D converter to sample and a built-in DSP calculation to simulate the transient
current wave of the tested components. Circuit principle is as follows:

Figure 4.6 Constant Impedance Mode

CZ Ranges

When working in CZ mode, you can Press the the key to enter the RANGE menu. Two overlapping ranges can be
selected: LOW RANGE or HIGH RANGE. Impedance can be edited in either of the two ranges.

Low range will supply higher accuracy and better resolution when you set lower impedance. If any value you set is outside
the maximum value of the LOW RANGE, you should select HIGH RANGE. If the electronic load is in remote control
mode, you can use the IMP:RANG command to switch impedance range.

CZ Vmax/Vmin Limits

These parameters refer to the voltage high and low limit for the automatic test mode. During automatic test mode, the
device under test (DUT) must be operating within the congured values for the test to PASS upon completion. If the
DUT operates outside the congured values, the test will FAIL upon completion.

Note:

These parameters are used for Automatic Test ONLY.

Immediate Impedance level

Set the impedance level via the front panel. If the load is in CZ mode, the new impedance level setting immediately
changes the input. If the load is not in CZ mode, the impedance level setting will be saved for use until mode is switched

to CZ mode. Select the channel to be edited before setting impedance parameters. Press the the button to enter
CZ mode. After choosing the high-low range, the front panel will display the following:

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Operations 38

CH01
Rset = 7500.0 Ω
Vmax = 82 V
Vmin = 0 V
RLC R= 7500.0 Ω
RLC L = 0 uH
RLC C = 10 uF

Rset: set the impedance value (𝑅𝐿)
Vmax: set maximum voltage pass/fail limit for Automatic test mode
Vmin: set minimum voltage pass/fail limit for Automatic test mode
RLC R: set the series resistance value (𝑅𝑠)
RLC L: set the series inductance value (𝐿𝑠)
RLC C: set the parallel capacitance value (𝐶𝐿)

4.1.5.1 Setting CV,CC,CR, CW,CZ Mode

To set up an operation mode from the front panel:

1. Power on the electronic load. Self-test

2. Press the keys to select the channel to be edited, such as channel 1. CH01 CC OFF

3. Press the the key to enter the channel setup menu.

4. Press the the key to enter the Mode menu.

5. Press the the key to select CV, CC, CR, CW, or CZ mode.

– Press the the key to conrm.

6. Press the the key to select the Range menu.

– Press the the key to conrm

7. Press the the key to select Low Range or High Range.

– Press the the key to conrm

8. Press the the key to select the voltage setting Vset, current setting Iset, resistance setting Rset, power setting,
or impedance setting.

– Press the the key to conrm.

9. Press the key to select the rise slope setting ∫. Input the value and Press the

– Input the value and Press the the key to conrm. (CC mode only)

10. Press the the key to select the fall slope setting ∫.

– Input the value and Press the the key to conrm. (CC mode only)

11. Press the the key to exit.

12. Press the the key to turn on the load’s input.

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Operations 39

4.2 Local Operations

4.2.1 Mainframe Panel

The front panel keys are eective only in the local mode. When the load is powered on, it works in local mode
automatically (unless any of the remote interfaces are connected to a device controlling it). Select a channel number and
set parameters such as voltage or current via the front panel keys. When the load is repowered on, the mainframe will
scan all the installed modules once again, and can recall the parameters from the last time it was powered o.

Figure 4.7 MDL4U001 Mainframe Front Panel

1. VFD Display
When powering on, the VFD screen will light up and show the instrument’s rmware version. Then the system will
begin power-on self-test, check all the installed modules of the load, and display every channel’s number, voltage,
and current measurements.

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Operations 40

2. Function Keys

Key Description

Chan

Save

Recall This key can be used to quickly recall a saved group of parameters from memory.

Setup

On/O

Trig

Start This key is used to start an automatic test.

Pause

This key is used to switch channels. Every module has its own channel number and can be selected
from the mainframe panel.
This key is used to save parameters. After selecting a channel and editing its parameters, Press the the
Save key to save your settings into non-volatile memory. Up to 101 groups of parameters can be saved.

This key is used to enter the specic channel’s menu. For example, Press theing this key allows you to
set up A/B transient mode and CC/CV/CR/CW/CZ mode. For more details, view the Menu List sec­tion.

This key is used to turn the module’s input state on or o. When the synchronization function in the
channel menu is enabled, Press theing this key can control the on/o state of all channels.
This key is used to trigger the electronic load. Select the Manual Trigger mode to use front panel trig­gering.

This key is used to pause an automatic test. The VFD will display pausing at each step. Press the the
key again to test the le continuously.

Table 4.1 Function Keys

3. Entry/Shift Key

Key Description

Numeric Keys These are number input keys.

This key can be used to exit any working state.

This key is used for decimal.

These keys are used to move up and down the menu selection.

This key is used to conrm selection.

This key is used to enter other menus and functions.

+

(System)

+

(Cong)

+

(Program)

Press the this key combination to enter the System menu.

Press the this key combination to enter the Conguration menu.

Press the this key combination to enter the Program menu.

+

(Local)

+

(Lock)

4. Power Switch
Turns the electronic load on or o.

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Press the this key to switch the electronic load to local mode when in remote sense mode.

Press the this key to lock the module’s panel keys and knob. RePress the the button to un­lock.

Table 4.2 Entry/Shift Key

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Operations 41

4.2.2 Module Panel

Figure 4.8 Module Front Panel

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Operations 42

1. VDF Display Bright VFD display shows module‘s operating mode.

2. Panel Keys

Key Description

A/B

(single channel modules)

L/R

(dual-channel modules)

Short Used for short testing. This allows the load to simulate a short circuit at the input.

Mode Switches the operating mode (CC, CR, CV, CW, or CZ).

Tran

On/O Control module’s input on/o state

Switch A/B transient preset value.

Switch the left/right channels. Press the this key + rotary knob to control the two chan­nels.

Move the cursor position. Press the key to move the cursor to the position you want to
edit, and then use the rotary knob to adjust value.

Selects the transient mode. Press the this key rst to enable transient mode before run­ning A/B transient operation and then send the triggering signal to run a program.

Table 4.3 Entry/Shift Key

3. Rotary Knob Used to change parameter values.

4. Air Inlet
Module’s air intlet for cooling purposes.

Warning:

Do not place any objects that may block or cover air inlet.

4.2.3 Module Panel Lock

Press the the + keys to lock the selected channel’s keys and knob operation. To unlock, Press the the

+ again.

4.3 Switching Channels

There are three ways to switch channels:

1. Press the the + number keys.

2. Press the the + keys.

3. Press the the number key of the channel in the Setup menu.

4.4 Channel Synchronization

To change the synchronization of the channels:

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Operations 43

1. Switch to the channel on the mainframe.

2. Press the + key to enter the Conguration menu.

3. Select and enter the SYNC ON SET submenu.

4. Select ON or OFF.

5. When enabled, the key can control the input state of the corresponding module synchronously.

Note:

The same method can be used to set up synchronization with other channels. When in remote control mode, the
SCPI command INPut:ALL ON is used to synchronously load all channels.

4.5 Module VFD Indicator Function Description

Figure 4.9 indicates

Figure 4.9 Load Module VFD Panel

L/R

The indicator of the dual-channel module’s left/right channel. If you want to edit left/right channel parameters, rst
select the channel using the L/R key. Single-channel module will always display R.

OFF

Indicates that the module input is o. When module input is enabled, OFF indicator will turn o.

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Operations 44

CC/CV/CR/CW/CZ

Indicates the module’s operating mode.

VFD Display Screen

Shows four lines of numbers. The rst line shows the measured voltage value. The second line shows the measured
current value. The third line shows the measured circuit’s power value. The fourth line shows the setup value, and users
can set A/V/Ω value here.

Short

Is displayed when short circuit function is enabled on the module.

Tran

Is displayed when TRANSIENT mode is enabled on the module.

List

Is displayed when selecting LIST mode in the Conguration menu.

Sense

Is enabled in remote sense function. There is no need to set this in the menu, as you only need to link the circuit to
remote sense terminals and ‘Sense’ will be displayed.

4.6 Transient Operation

Transient operation enables the module to periodically switch between two load levels, as might be required for testing
power supplies. Transient operation can be turned on and o from the front panel (Tran and Trig keys). The parameters
of the transient operation include: A level, A width, B level, B width, and transient testing modes.

There are three dierent transient testing modes: continuous, pulse, and toggle.

Mode Description

Continuous Generates a respective pulse stream that toggles between two load levels.

Pulse Generates a load change that returns to its original state after some time period.

Generates a repetitive pulse stream that toggles between two load levels. It is similar to con-

Toggle

tinuous mode except that the transient points are controlled by explicit triggers instead of an
internal transient generator.

Table 4.4 Transient Modes

4.6.1 Continuous

The electronic load generates a repetitive pulse stream that toggles between two load levels. The load switches the state
between two value settings, value A and value B.

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Operations 45

In CC mode, transient testing can be used to check the stability of the source voltage. Transient functions have two
current levels (A level, B level), which should be in the same range (high range or low range). You can set the A/B level
delay time and the rise/fall slew rate via the mainframe keypad.

The slew rate determines the rate at which the level changes. Press the Trig key, and the load will continuously switch
between the A/B levels preset. Transient loads are usually used to test the power supply’s performance under continuous
changing load conditions. Figure 4.10 shows the current waveform of continuous transient operation mode.

Figure 4.10 Continuous Transient Operation

4.6.2 Pulse

The elctronic load generates a transient pulse of programmable width when pulse transient operation is in eect.

In pulse mode, you can set A/B level, A/B width, and A/B slew rate via the mainframe keypad. The electronic load will
automatically switch to A level after maintaining A width time. Then it will switch to B level. The electronic load will
not switch to A level again until the instrument receives the pulse signal. The gure 4.11 shows the current waveform
in pulse transient operation.

Figure 4.11 Pulse Transient Operation

4.6.3 Toggle

The lectronic load will switch between A level and B level when receiving a trigger signal after the transient operation is
enabled. The following picture shows the current waveform in toggle transient operation.

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Operations 46

Figure 4.12 Toggle Transient Operation

4.6.4 Setting Up A/B Transient Operation

Thee following is a short tutorial of how to set up A/B transient operation for the electronic load. In this example, the
up rise speed at is set to 1 A/us and fall speed at 2 A/us. The electronic load will be in continuous transient mode and
switch between 10 A and 2 A in durations of 0.002 s and 0.003 s respectively.

Note:

When setting up steps, make sure all transient level, slew, and width parameters are within the modules’ specied
limits.

1. Power on the electronic load.

2. Press the keys to select the channel to be edited. In this example, we select channel 1.

3. Press the to enter the channel setup menu.

4. Select Mode and Press the to change the operating mode to CC mode. Press the to conrm.

5. Press the key to select Range setting and press the key.

6. Press the key to select LOW RANGE and press the key to conrm.

7. Press the key to select the rise slope setting ∫ and press the .

For 1A/us, input 1 and Press the key to conrm.

8. Press the key to select the fall slope setting ∫ and press the key.

For 2A/us, input 2 and Press the key to conrm.

9. Press the key to select A level setting TRANa and press the key.

For 10A, input 10 and Press the key to conrm.

10. Press the key to select A width setting Ta and press the key.

For 0.002s, input .002 and Press the key to conrm.

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Operations 47

11. Press the key to select B level setting TRANb and press the key.

For 2A, input 2 and Press the key to conrm.

12. Press the key to select B width setting Tb and press the key.

For 0.003s, input .003 and Press the key to conrm.

13. Press the key to select transient operation mode Tmode and press the key.

14. Select Continuous and press the key to conrm.

15. Press the key to exit.

16. Press the + to enter the System menu.

17. Press the key to select Trigger Source and press the .

18. Select Manual and press the key to conrm.

19. Press the key to exit.

20. Press the key to turn on the electronic load’s input.

21. Press the key on channel 1 module to enable transient operation.

22. Press the key on mainframe panel to trigger transient operation

Transient Operation Programming Example

In remote mode, the following commands can be used to setup the same parameters used in the tutorial above. (refer
to MDL4U Series Programming Guide for more information).

CURRent:TRANsient:MODE CONTinuous

CURRent:TRANsient:ALEVel 10

CURRent:TRANsient:AWIDth 0.2ms

CURRent:TRANsient:BLEVel 2

CURRent:TRANsient:BWIDth 0.3ms

TRANsient ON

TRIGger:IMMediate

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Operations 48

4.7 List Operation

List mode lets you generate complex sequences of input changes on a single channel with rapid and precise timing, which
may be synchronized with internal or external signals. This is useful when running test sequences with a minimum amount
of overhead.

The parameters of List operation include the name, number of steps (2-84), step width time (20 us 3600 s), and every
steps’ set value and slew rate. The list le can be saved in non-volatile memory where it can be quickly recalled. Up to
7 groups of List les in CC mode only can be edited.

In List operation mode, the electronic load begins to enable the List operation when it receives the trigger signal and will
continue until the List operation is completed or the instrument receives another trigger signal

Figure 4.13 List Operation

4.7.1 Setting Up List Operation Mode

The following is a quick tutorial of how to set up List Mode for your electronic load.

1. Power on the electronic load.

2. Press the keys to select the channel to be edited.

3. Press the + to enter the System menu.

4. Press the key to select Trigger source and press the key.

5. Select Manual and press the key to conrm.

6. If electronic load is on, press the key to turn o the electronic load’s input.

7. Press the + to enter the Conguration menu.

8. Press the key to select List and press the key.

9. Press the key to select Edit List and press the key.

10. Press the key to select high range or low range and press the key to conrm.

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Operations 49

11. Input number of steps in the List.

Input value and press the key to conrm.

12. Set rst step’s current level. Input value and press the key to conrm.

13. Set rst step’s slew rate. Input value and press the key to conrm.

14. Set rst step’s width time. Input value and press the key to conrm.

15. Set second step’s current level. Input value and press the key to conrm.

16. Set second step’s slew rate. Input value and press the key to conrm.

17. Set second step’s width time. Input value and press the key to conrm.

18. Set parameters for steps 3 through 5 in the same manner described above.

19. Set number of run cycles. Input value and press the key to conrm.

20. Select memory position to save list le. Input value and press the key to conrm.

21. Press the key to select Function Mode and press the .

22. Select List and press the to conrm.

23. Press the key twice to exit menus.

24. Press the key to turn on the electronic load’s input.

25. Press the key to trigger List mode operation.

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Operations 50

List Mode Programming Example

In remote mode, the following commands can be used to setup the same parameters used in the tutorial above. (refer
to MDL4U Series Programming Guide for more information).

Command

LIST:RANGe

LIST:COUNT

LIST:STEP

LIST:LEVEL

LIST:SLEW

LIST:WIDTH

LIST:LEVEL

LIST:SLEW

LIST:WIDTH

LIST:SAV

LIST:RCL

FUNCTION:MODE LIST

TRIG:SOUR BUS

*TRG

Function

40 Sets List range

10000 Sets List cycle

Sets List steps

Sets List step 1 level

Sets List step 1 slew rate

Sets List step 1 width

Sets List step 2 level

Sets List step 2 slew rate

Sets List step 2 width

Saves List to le 2

Recalls List le 2

Sets List mode function

Sets trigger source

Runs List le

Note:

This example programs a list on a MDL4U200 module. For other models, make sure all range, level, slew, and tran­sient width parameters are within the modules’ specied limits.

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Operations 51

4.8 Trigger Operation

The trigger operation can be used in the following operations: transient pulse output, triggered output, and list output.
The electronic load has ve kinds of trigger modes to synchronously trigger the tested instrument. Before enabling the
trigger function, the trigger source must be selected.

4.8.1 Manual Trigger

When manual trigger mode is active, pressing the Trig key on the front panel will enable a trigger operation.

4.8.2 External Trigger Signal(TTL level)

The 1𝑠𝑡 pin of the 8-pin connector on the rear panel of the mainframe is the trigger input terminal. When an external
trigger signal is available, input a low pulse (>10us) to the input and the load will enable a trigger operation.

4.8.3 Hold Trigger

When hold trigger is used, the load will enable a trigger operation only when the load receives the TRIG:IMM trigger
command from the communication port.

4.8.4 Bust Trigger

When bus trigger is set, the load will enable a trigger operation as soon as the load receives the trigger command GET
or *TRG.

4.8.5 Timer Trigger

When timer trigger is set, the mainframe will enable a trigger operation periodically.

4.9 Short Operation

The electronic load can simulate a short circuit at its input. During front panel operation, press the key to switch
the short on/o state. Short operation will not aect the present setting. When turning o the short state, the load
returns to the original set state.

The actual value of the electronic load in short operation depends on the mode and range that is active when the short
is turned on. In CC or CR mode, the maximum short current is 120% of the current range. In CV mode, short means
setting the load’s constant voltage to be 0 V. In short operation mode, you can measure the maximum short current
(Amax) or DC current (ADC) of the power source to be measured. This function via the Conguration menu. When in
remote control mode, send the SCPI command INPut:SHORt ON to enable the short operation.

4.10 Input On/O Operation

During front panel operation, press the f key to switch the input on/o state. Input On/O operation will not aect
the present settings. The load/unload speed of On/O operation is not dependent on the rise/fall slew rate. When in
remote control mode, send the SCPI command “INPut ON” to turn the input on (refer to MDL4U Series Programming
Guide for more information on remote commands).

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Operations 52

4.11 Von Operation

The Von voltage value can be set to control the voltage turn on state for the electronic load. When the input voltage
exceeds the Von voltage value, the electronic load’s input state turns on.

This function can protect a DUT when its voltage goes below a specied level. For example, when testing a power
supply’s discharge, you can set the voltage level for the power supply to begin and end discharging.

There are two dierent modes of Von operation, set by the Von LATCH parameter. When Von LATCH is disabled, the
electronic load will begin sinking current if input voltage exceeds Von voltage. When the input voltage drops below the
Von voltage value, the electronic load will stop sinking current and the input will turn o.

Figure 4.14 Von LATCH Load’s Working Range

When Von LATCH is enabled, the electronic load will begin sinking current if input voltage exceeds Von voltage. When
the input voltage drops below the Von voltage value, the electronic load will still continue to sink current and the input
remains on.

Setting Up the Von Function

The following is a quick tutorial of how to set up the Von function for your electronic load. In this example, Channel 1
Von is enabled and set to 5 V.

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Operations 53

Figure 4.15 Von LATCH Load’s Working Range

1. Power on the electronic load. Self-test

2. Select channel to be set up. Press the 1 for channel 1.

3. Press the + to enter Conguration menu.

4. Press the to select Von and press the .

5. Select Von Point and press the key.

6. Set the Von Point. Input 5 and press the to conrm.

7. Press the key to select Von Latch and press the key.

8. Select On and press the key to conrm.

9. Press the key twice to exit menus.

10. Press the key to turn on the electronic load’s input. The electronic load will begin sinking current at 5 V.

When in remote control mode, you can send SCPI command “VOLT:ON n” to set Von value; send “VOLT:LATch ON”
to enable Von LATCH function.

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Operations 54

4.12 Save and Recall Operation

The stored settings of all channels can be recalled. The stored parameters include operation mode, voltage/current
values, slew rate, transient setting, and more. Up to 101 groups of setting parameters can be saved. Group 0 can be
used for power-up settings. Groups 1 through 100 can be used for automatic testing parameters. All parameters are
saved into non-volatile memory and will remain saved even in a powered down state.

To save the channel’s settings:

1. After setting up your parameters, press the key to save. It will ask for the Save Group number.

2. Input the Save Group number (0-100) and press to conrm.

To recall previously saved settings:

1. Press the key. It will ask for the Recall Group number.

2. Input the Group number (0-100) you previously saved your parameters to and press key to recall.

4.13 Module Controlling Link

There is an 8-pin terminal and current monitoring connector on every module’s rear panel.

Figure 4.16 Single-Channel Control Module Link

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Operations 55

Pin Signal Description

1 GND Ground
2 VF Voltage fault indication terminal
3 DI Digital input terminal
4 DO Digital output terminal

I OUT Current monitoring output
5 SENSE + Voltage remote measuring terminal ( + )
6 SENSE - Voltage remote measuring terminal ( - )
7 EXT_PRG+ External analog controlling terminal ( + )
8 EXT_PRG- External analog controlling terminal ( - )

Table 4.5 Module Terminal Pinout

4.13.1 Voltage Failure Indication

When the electronic load is under OVP or reverse protection condition, pin 2 (VF) will output a high level signal.

4.13.2 Current Monitoring

The current monitoring terminal will output 0-10 V analog signal accordingly to 0 - full range of the input current. You
can connect an external voltmeter or an oscilloscope to display the input current’s change.

4.13.3 Digital I/O

Digital I/O is pin 3 and pin 4 shown in gure 4.16 and only used in remote control. The digital input terminal (pin 3)
can detect a high/low level signal. The digital output terminal (pin 4) can output a TTL high/low level signal. It is a
universal output terminal and can be used to control an external instrument.

4.13.4 Remote Sense Function

When working in CC, CV, and CR mode, if the electronic load consumes a very large current, it will cause a voltage drop
in the leads between the connected device and terminals of the electronic load. In order to ensure testing accuracy, the
electronic load provides a pair of remote sensing terminals in the rear panel where users can sense the output terminal
voltage of the connected device. Set the electronic load to REMOTE SENSE mode before using this function. On the
rear terminals, SENSE (+) and SENSE (–) are the remote sensing inputs. By eliminating the eect of the voltage drop
in the load leads, remote sensing provides greater accuracy by allowing the electronic load to regulate directly at the
source’s output terminals (see Figure 3.1).

4.13.5 External Analog Control

Controls the current setting of the electronic load in CC mode using the external analog programming terminal, pin 7
and pin 8. A 0-10 V input signal will simulate 0 – full scale of the electronic load to regulate the input current of the
electronic load (10 V indicates the full range of electronic load’s current rating)

Note:

External analog control is designed to be used when the instrument is set to High range (full range) only. If low
range is used, the 0-10 V input signal may not reect the full scale input range of the load.

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Operations 56

4.14 Automatic Test

The automatic test function of the MDL4U Series electronic load is useful for simulating various tests and allows the
user to edit up to 10 program les. Each le has 10 steps and up to 100 steps can be edited and saved into the
EEPROM. Convenient for production environments, automatic test can cascade sequences across multiple channels and
allows setting of Pass/Fail (P/F) criteria.

4.15 Conguring Pass/Fail Paramters

The Pass/Fail criteria can be found in the SETUP menu of the front panel, under the Vmax/Vmin (CC/CR/CW/CZ
mode) or Amax/Amin (CV mode) parameters. Set Pass/Fail criteria for each mode used in the Automatic test sequence
before running the automated test.

4.15.1 Conguring Instrument Settings

The automatic test runs a program that uses the settings stored into the internal EEPROM memory. Each program can
run 10 sequences, and each of these sequences is correlated to instrument settings that are stored within a designated
group of internal EEPROM memory. They are designated according to the table below:

Save Table

PROGRAM 1

Sequence

Save Group 1 2 3 4 5 6 7 8 9 10

PROGRAM 2

Sequence

Save Group 11 12 13 14 15 16 17 18 19 20

PROGRAM 3

Sequence

Save Group 21 22 23 24 25 26 27 28 29 30

PROGRAM 4

Sequence

Save Group 31 32 33 34 35 36 37 38 39 40

PROGRAM 5

Sequence

Save Group 41 42 43 44 45 46 47 48 49 50

PROGRAM 6

Sequence

Save Group 51 52 53 54 55 56 57 58 59 60

PROGRAM 7

Sequence

Save Group 61 62 63 64 65 66 67 68 69 70

PROGRAM 8

Sequence

Save Group 71 72 73 74 75 76 77 78 79 80

PROGRAM 9

Sequence

Save Group 81 82 83 84 85 86 87 88 89 90

PROGRAM 10

Sequence

Save Group 91 92 93 94 95 96 97 98 99 100

1 2 3 4 5 6 7 8 9 10

1 2 3 4 5 6 7 8 9 10

1 2 3 4 5 6 7 8 9 10

1 2 3 4 5 6 7 8 9 10

1 2 3 4 5 6 7 8 9 10

1 2 3 4 5 6 7 8 9 10

1 2 3 4 5 6 7 8 9 10

1 2 3 4 5 6 7 8 9 10

1 2 3 4 5 6 7 8 9 10

1 2 3 4 5 6 7 8 9 10

Table 4.6 Save Table

The following is a step-by-step tutorial on how to set up a test le

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Operations 57

1. Power on the electronic load. Self-test

2. Select the channel you want to edit and then edit every group’s step. For this example, we will select channel 3 and
channel 5 below. Press the keys to switch channel to 3.

3. Press the key to enter the channel setup menu.

4. Press the key to enter the Mode menu.

5. Press the key to select the operating mode. Every step’s mode can be edited. Press the key to conrm.

6. Press the key to select ISet.

7. Press the to enter the menu and set the working current. For example, to set 1A, press the and then

to conrm.

8. Press the key to move the cursor to Vmax=82.000V and press the to set the upper limit of testing
voltage. In this example, the rst step is 5.8V.

– Press the and then to conrm.

9. Press the key to move the cursor to Vmin=0.000V and press the to set the lower limit of testing voltage.
In this example, the rst step is 0.15V.

– Press the and then to conrm.

10. After editing the rst step of channel 3, press the key to exit the menu.

11. Press the keys to select channel 5. To edit the rst step of channel 5, repeat steps 3 through 6 with desired
parameters.

12. After editing the rst step of channel 5, press the key to exit the menu.

13. Save the edited rst step of channel 3 and channel 5.

– Press the and to save step 1.

– Press the to conrm.

14. In the same manner, edit the rest of the steps for channel 3 and channel 5 by repeating steps 2 through 10 above.
These saved groups correspond to sequences that will be selected in your program below.

15. Press the + key to enter the Program menu.

16. Press the key to select Edit Program and press the key.

17. The MDL4U Series with mainframe extension can support a maximum of 16 channels. 0 represents the MDL4U001
mainframe and 1 represents the MDL4U002 mainframe extension. 7531 indicates channels 1, 3, 5, and 7 have been
equipped with electronic load modules.

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Operations 58

18. Select the channels to be tested.

– For instance, to select channels 3 and 5, press the number keys 3 and 5. ‘Y’ denotes the channel is selected.

– To cancel a channel, press the the number key again to cancel.

– Then press the to conrm your selection.

19. Select the steps needed to test.

– For example, to test 4 steps, press the 1 2 3 4 (0 stands for the tenth step).

– To cancel a step, press the the number key again to cancel.

– Press the to conrm your selection.

20. To suspend a step, press the the number key of the step.

– For example, to suspend step 2, press the 2. Press the the number key again to cancel.

– Then press the to conrm your selection.

21. To edit the rst step of the 4 steps, determine whether a short circuit testing on channel 3 and 5 is needed.

– For example, if channel 3 needs short circuit testing, input 3.

– Then press the to conrm your selection.

22. Set load on time (Ton).

– For example, if you need 2s, input 2 and then press the key to conrm.

23. Set load o time (To).

– For example, if you need 2s, input 2 and then press the key to conrm.

24. Set test delay time (Tpf).

– For example, if 1s is needed, input 1and then press the key to conrm.

Figure 4.17 pf Delay Time

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Operations 59

25. Repeat steps 17 through 20 and set the rest of the steps’ load on/o time.

26. Set condition for when to stop testing.

– COMPLETE means to stop test when all steps are completed.

– FAILURE means to stop test when testing fails.

– Press the keys to select condition and press the to conrm.

27. Program chain is used when you need to link to the next le to be tested.

– For example, to link to group 2, press the 2.

– If no other le needs to be linked, input and then press the key to conrm.

28. Save the edited les into the EEPROM. Up to 10 program les can be saved.

– For instance, press the 1 to save the edited le to program le 1 and then press the to conrm.

29. Press the key to exit menu.

4.15.2 Recall Test Files

The following is a procedure on how to recall edited test les from the EEPROM:

1. Press + to enter the Program menu.

2. Press key to select Recall Prog and press .

3. Input the saved program number and press to recall the saved testing le.

4. To run the program, press key to select Run Program and press .

5. Press key to start automatic testing.

– To pause, press key and then press key to continue.

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Operations 60

4.16 Remote Operation

There are four types of communication interfaces available: USB, Ethernet, GPIB, and RS232.

Figure 4.18 Communication Interfaces

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Operations 61

4.16.1 USB Interface

Use Type A to Type B USB cables to connect the electronic load and the PC. All electronic load functions are program-

mable over the USB. Press + on the front panel to enter the System menu. Select Communication and
choose USBTMC-USB488.

The USB488 interface capabilities of the electronic load are described below:

• The interface is IEEE 488.2 standard USB488 interface.

• The interface accepts REN_CONTROL, GO_TO_LOCAL, and LOCAL_LOCKOUT requests.

• The interface accepts MsgID = TRIGGER USBTMC command message and forwards TRIGGER requests to the
function layer.

The USB488 device capabilities of the electronic load are described below:

• The device understands all mandatory SCPI commands.

• The device is SR1 capable.

• The device is RL1 capable.

• The device is DT1 capable.

4.16.2 Ethernet Interface

Use a network cable to connect PC through Ethernet interface of the electronic load. Press + on the front
panel to enter the System menu. Select Communication and choose ETHERNET. Then select Ethernet Set to set
gateway address Gateway Set, IP address IP Set, mask address Mask set, and port port set.

4.16.3 GPIB Interface

First connect GPIB port of electronic load to GPIB card of PC. There must be sucient contact. Tighten the screws

and then set the address. The address can be set from 0 to 31. Press + key to enter the System menu.
Select Communication and choose GPIB. The electronic load operates from a GPIB address set from the front panel.

To set the GPIB address, press key to select GPIB Address. Input the address and press key to conrm.
The GPIB address is stored in non-volatile memory.

RS232 Interface

Use a cable with two COM interfaces (DB9) to connect the electronic load and PC. It can be activated by selecting

RS-232 in Communication of the System menu.

Note:

There are two COM interfaces on the rear panel of the MDL4U001 mainframe: the left 9-pin COM interface is the
RS-232 communication interface and the right 9-pin COM serial port connection is not for use.

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Operations 62

All SCPI commands are available through RS-232 programming. The EIA RS-232 standard denes the interconnections
between data terminal equipment (DTE) and data communications equipment (DCE). The electronic load is designed
to be a DTE and can be connected to another DTE such as a PC COM port through a null modem cable.

Note:

The RS-232 settings in your program must match the settings specied in the front panel System menu. Press

+ on the front panel to enter the System menu if you need to change the settings.

RS232 Data Format

The RS-232 data is a 10-bit word with one start bit and one stop bit.

Parity = None

The number of start and stop bits are not programmable. However, the following parameters are selectable in the System

menu using the front panel + key.

Start Bit

8 Data Bits

Stop Bits

Baud Rate

The System menu lets you select one of the following baud rates, which are stored in non-volatile memory: 4800, 9600,
19200, 38400, 57600, or 115200.

Parity

None - eight data bits without parity

Even - seven data bits with even parity

Odd - seven data bits with odd parity

RS232 Flow Control

The RS232 interface supports the following ow control options. For each case, the electronic load will send a maximum
of ve characters after hold-o is asserted by the controller. The electronic load is capable of receiving as many as fteen
additional characters after it asserts hold-o.

• CTS/RTS: The electronic load asserts its Request to Send (RTS) line to signal hold-o when its input buer is
almost full, and it interprets its Clear to Send (CTS) line as a hold-o signal from the controller.

• XON/XOFF: When the input queue of the electronic load becomes more than ¾ full, the instrument issues an X-OFF
command. The control program should respond to this and stop sending characters until the electronic load issues
the X-ON, which it will do once its input buer has dropped below half-full. The electronic load recognizes X_ON
and X_OFF sent from the controller. An X-OFF will cause the electronic load to stop outputting characters until it
sees an X-ON.

• NONE: No ow control.

Flow control options are stored in non-volatile memory.

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Operations 63

RS232 Connections

The RS-232 serial port can be connected to the serial port of a controller (i.e., personal computer) using a straight­through RS-232 cable terminated with DB-9 connectors. Do not use a null modem cable. Figure 33 shows the pinout
for the connector.

If your computer uses a DB-25 connector for the RS-232 interface, you will need a cable or adapter with a DB-25
connector on one end and a DB-9 connector on the other. It must be a straightthrough (not null modem) a cable.

Pin Number Signal Function

1 NC No Connection
2 TXD Transmit Data
3 RXD Receive Data
4 NC No Connection
5 GND Ground
6 NC No Connection
7 CTS Clear to Send
8 RTS Ready to Send
9 NC No Connection

Figure 4.19 DB9 Pinout

Table 4.7 DB9 Pinout

RS232 Troubleshooting

If you are having trouble communicating over the RS-232 interface, check the following:

• The computer and the electronic load must be congured for the same baud rate, parity, number of data bits, and
ow control options. Note that the electronic load is congured for 1 start bit and 1 stop bit (these values are xed).

• The correct interface cables or adapters must be used, as described under the RS-232 connector. Note that even if
the cable has the proper connectors for your system, the internal wiring may be incorrect.

• The interface cable must be connected to the correct serial port on your computer (COM1, COM2, etc.) and the
correct 9-pin serial port on the mainframe.

Communication Settings

Before communicating, please make sure that the following parameters of the electronic load match that of the PC. You
can enter the System menu (Shift + ) to make any changes.

Baud rate : 9600 (5800, 9600, 19200, 38400, 57600, 115200)

Data bit : 8

Stop bit : 1

Parity : None (None, Even, Odd)

Local address : 0 (0 through 31, default setting is 0)

Note:

When communicating with a PC, you can only use one communication interface at a time.

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Specications

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Specications 65

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