B+K precision 1688B User manual

Model 1685B, 1687B, 1688B
Switching DC Power Supply
INSTRUCTION MANUAL

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1 Safety Summary
The following safety precautions apply to both operating and maintenance personnel and
must be observed during all phases of operation, service, and repair of this instrument. Before
applying power, follow the installation instructions and become familiar with the operating
instructions for this instrument.
GROUND THE INSTRUMENT
To minimize shock hazard, the instrument chassis and cabinet must be connected to
an electrical ground. This instrument is grounded through the ground conductor of
the supplied, three-conductor ac power cable. The power cable must be plugged
into an approved three-conductor electrical outlet. Do not alter the ground
connection. Without the protective ground connection, all accessible conductive
parts (including control knobs) can render an electric shock. The power jack and
mating plug of the power cable meet IEC safety standards.
DO NOT OPERATE IN AN EXPLOSIVE ATMOSPHERE
Do not operate the instrument in the presence of flammable gases or fumes.
Operation of any electrical instrument in such an environment constitutes a definite
safety hazard.
KEEP AWAY FROM LIVE CIRCUITS
Instrument covers must not be removed by operating personnel. Component
replacement and internal adjustments must be made by qualified maintenance
personnel. Disconnect the power cord before removing the instrument covers and
replacing components. Under certain conditions, even with the power cable
removed, dangerous voltages may exist. To avoid injuries, always disconnect power
and discharge circuits before touching them.
DO NOT SERVICE OR ADJUST ALONE
Do not attempt any internal service or adjustment unless another person, capable of
rendering first aid and resuscitation, is present.
DO NOT SUBSTITUTE PARTS OR MODIFY THE INSTRUMENT
Do not install substitute parts or perform any unauthorized modifications to this
instrument. Return the instrument to B&K Precision for service and repair to ensure
that safety features are maintained.

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WARNINGS AND CAUTIONS
WARNING and CAUTION statements, such as the following examples, denote a
hazard and appear throughout this manual. Follow all instructions contained in
these statements.
A WARNING statement calls attention to an operating procedure, practice, or
condition, which, if not followed correctly, could result in injury or death to
personnel.
A CAUTION statement calls attention to an operating procedure, practice, or
condition, which, if not followed correctly, could result in damage to or destruction
of parts or the entire product.
WARNING:
Do not alter the ground connection. Without the protective ground
connection, all accessible conductive parts (including control knobs)
can render an electric shock. The power jack and mating plug of the
power cable meet IEC safety standards.
WARNING:
To avoid electrical shock hazard, disconnect power cord before
removing covers. Refer servicing to qualified personnel.
CAUTION:
Before connecting the line cord to the AC mains, check the rear panel
AC line voltage indicator. Applying a line voltage other than the
indicated voltage can destroy the AC line fuses. For continued fire
protection, replace fuses only with those of the specified voltage and
current ratings.
CAUTION:
This product uses components which can be damaged by electro-
static discharge (ESD). To avoid damage, be sure to follow proper
procedures for handling, storing and transporting parts and
subassemblies which contain ESD-sensitive components.
SAFETY SYMBOLS
This symbol on an instrument indicates that the user should refer to the
operating instructions located in the manual.
Certification
We certify that this product met its published specifications at time of shipment from the
factory.

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Compliance Statements
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.

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Contents
1 Safety Summary........................................................................................ 1
2 Introduction.............................................................................................. 6
3 Controls and Indicators............................................................................. 7
3.1 Front Panel........................................................................................ 7
3.2 Rear Panel ......................................................................................... 8
4 Operating Instructions.............................................................................. 9
4.1 Using the Power Supply .................................................................. 10
4.1.1 Connection.............................................................................. 10
4.1.2 Self Test Sequence .................................................................. 10
4.1.3 Control Knobs.......................................................................... 12
4.1.4 Manually Zeroing Current Meter Offset ................................. 13
4.1.5 Using Both Main and Auxiliary Outputs.................................. 14
4.2 Control Modes ................................................................................ 14
4.2.1 Normal Mode.......................................................................... 15
4.2.2 Preset Mode............................................................................ 15
4.2.3 Analog Remote Control Mode ................................................ 16
4.2.4 Set Mode................................................................................. 16
5 Remote Control....................................................................................... 18
5.1 Analog Remote Control................................................................... 18

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5.1.1 Using Two External Variable DC Voltage Sources................... 20
5.1.2 Using Two 5 kΩ Variable Resistors.......................................... 21
5.1.3 Enable and Disable the Output ............................................... 23
5.2 PC Interface Control........................................................................ 23
6 Faults and Troubleshooting .................................................................... 24
6.1 OVP: Overvoltage Protection......................................................... 24
6.2 OTP: Overtemperature Protection................................................. 24
6.3 OLP: Overload Protection............................................................... 25
6.4 Upper Voltage Limit (UVL) and Upper Current Limit (UCL) ............ 26
6.5 Fuse Replacement........................................................................... 27
7 Specifications.......................................................................................... 28
8 Certification ............................................................................................ 30
9 Service Information ................................................................................ 31
10 Limited Two-Year Warranty.................................................................... 32

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2 Introduction
B&K Precision models 1685B, 1687B, and 1688B are laboratory grade switching mode
DC power supplies with high current output in a small form factor and lightweight
package. The 1685B Series provides various configurations of output voltage and
current, and makes setting voltage and current levels fast and precise through its
dual action, coarse/fine rotary encoder control knobs. In addition to its constant
voltage (CV) and constant current (CC) modes, the high efficiency DC power supply
offers a unique solution with its preset and analog remote control modes. Save up to
three different presets of voltage and current values for quick recall. The analog
remote control function allows the output power, voltage, and current to be adjusted
without touching the front panel of the power supply. These features make the
1685B Series suitable for a wide range of applications including production testing,
telecommunications, R&D, service, and university labs.
Features
Automatic CV/CC crossover operation
Lightweight and compact
Rotary encoder control for precise voltage and current setting
Save up to 3 user-defined voltage and current presets for quick recall
PC software for remote control and external timed programming
Analog remote control function
USB interface
Front panel auxiliary output
Overvoltage, over temperature, and overload protection

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3 Controls and Indicators
3.1 Front Panel
Figure 1 - Front Panel
(1) LED panel meter display with CV/CC indicator
(2) Rear Control Indicator (lights up when using Preset/Remote Control/Set mode)
(3) Output Voltage Control Knob (control main and auxiliary output voltage)
(4) Output Current Control Knob (control main and auxiliary output current limit)
(5) Power ON/OFF Switch
(6) Auxiliary Output Terminal (max 5 A)
Note: Please see Section 4.1.5 more details on using both main and
auxiliary output terminals together.

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3.2 Rear Panel
Figure 2 - Rear Panel
(7) Main Output Terminal (max 5 A for 1685B / 10 A for 1687B / 20 A for 1688B)
Note: Please see Section 4.1.5 for more details on using both main and
auxiliary output terminals together.
(8) Mode Selection Switch (Normal, Preset, Remote Control, Set Modes)
(9) Recall Preset Selection Switch
(10) Analog Remote Control Terminal
(11) Cooling Fan Air Intake Grille
(12) AC Input Plug and Fuse Compartment
(13) USB Port (for PC remote control)

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4 Operating Instructions
Safety Precautions
●This power supply is for indoor use only.
● Do not expose the power supply to sun, high humidity, or dusty
environments.
●Never remove the metal cover of the power supply while AC power is
connected.
●Never touch the unit when your hands are wet.
●Never block the ventilation slots and cooling fan air intake window.
●Never attempt to repair the power supply. Incorrect re-assembly may
result in a risk of electric shock or fire.
●Never use the power supply for a load requiring higher current than the
designed value. Otherwise it may damage the power supply.
●Place the power supply on a flat surface with sufficient clearance and dry,
dust-free surroundings for ventilation.
This series has three models with different output voltage and current ranges. Make
sure you have purchased the correct one.
Model Number
Output Voltage Range
Total Rated Current
1685B
1 –60 V
0 –5 A
1687B
1 –36 V
0 –10 A
1688B
1 –18 V
0 –20 A
Table 1 - Model Table

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4.1 Using the Power Supply
4.1.1 Connection
To connect the equipment to the power supply, follow the steps below.
1. Check the rating label of the power supply and confirm that it complies with
your AC mains voltage.
2. Connect the power supply to the AC mains using the provided power cord
and make sure the Mode Selection Switch is in the Normal position.
3. Hook up the red (+) terminal to the positive polarity input of the equipment
and the black (-) terminal to the negative polarity input of the equipment.
4. Switch on the power supply first. The panel meter and green CV indicator
should light up again.
5. Switch on the equipment. The panel meter and green CV indicator should
still remain green.
6. When an operation is finished, switch off the equipment first and then
switch off the power supply.
4.1.2 Self-Test Sequence
The power supply will perform a series of self-checks when it is switched on. The
table below shows the self-test sequence.
Front Panel Display
Test
Show software version

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Front Panel Display
Test
Segment check
Constant Voltage mode
indicator check
Constant Current mode
indicator check
Rear control indicator
check
Return to Constant
Voltage mode
Start power supply checks
Overvoltage protection
check
Overload protection check

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Front Panel Display
Test
Overtemperature
protection check
Fan check
Output off (remote
control mode)
Table 2 - Self Test Sequence
The LED and other indicators on the front panel will be turned on. When the cooling
fan is being checked, a loud fan noise can be heard.
After the self-checks, the CV, V, and A LED indicators are lit up displaying voltage and
0.0 current. To find out about the set CC mode current level, just turn the current
control knob one click in either direction. The current display returns to 0.0 after a
few seconds.
4.1.3 Control Knobs
The rotary encoder control knobs have fine and coarse tuning with clicking
movement.
Push the knobs to toggle between coarse and fine tuning. You will notice the subtle
change in brightness of LED.
Adjust the knobs to your desired values through coarse and fine tuning. The display
will resume its normal brightness after a few seconds to confirm your adjustment.

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4.1.4 Manually Zeroing Current Meter Offset
The power supply will automatically zero the current meter offset when powered up.
In case it is needed to reset the current meter to zero during a test, you can manually
reset it to zero. This function can be used to zero meter readings < 1 A.
1. Press and hold the Voltage Control Knob for 30 s to enter Menu mode.
2. Rotate the Current Control Knob until the current meter displays “YES”.
3. Then press the Current Control Knob once to confirm. The “YES” will light up
after successfully zeroing current meter offset.
4. Finally, press the Voltage Control Knob to exit.

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4.1.5 Using Both Main and Auxiliary Outputs
The power supply has a main output in the rear and an auxiliary output in the front
that can be used separately or together.
The main and auxiliary output both share the same voltage and current control knobs
and will output the same voltage and current up to the maximum output ratings of
the power supply and terminals. When using both the main and auxiliary outputs
together, the power supply will automatically total the currents supplied to both
terminals up to the current limit of the power supply and show the total current on
the display.
For example, setting the voltage and current outputs for model 1688B (1-18 V, 0-20
A) to 18 V and 20 A would output 18 V at both main and auxiliary terminals and allow
you to draw up to a total of 20 A between the two terminals. If there is a 5 A load at
the auxiliary terminal, the most current you can draw from the main output is 15 A.
If the power supply reaches its set current limit at any time, the power supply will go
into CC mode and the loads together will draw up to the total value of the current
limit. Distribution of current between the main and auxiliary terminals will vary
depending on the loads.
Note: 1685B: Total rated current (Aux. + Main) is 5 A
1687B: Total rated current (Aux. + Main) is 10 A
1688B: Total rated current (Aux. + Main) is 20 A
4.2 Control Modes
There are four different control modes for the power supply:
Normal
Preset
Remote Control (Analog)
Set

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To select a mode, slide the Mode Selection Switch on the rear of the unit.
Figure 3 –Mode Selection Switch
Note: The power supply is factory preset to Normal Mode with maximum current
level.
4.2.1 Normal Mode
This is the factory preset mode and the power supply output voltage and current are
controlled by the dual action dial knobs.
Push the knobs to toggle the coarse and fine tuning. You will notice the subtle
change in brightness of LED.
Adjust the knobs to the desired values through coarse and fine tuning. To check the
preset current level, turn the Current Knob lightly in any direction.
The display will resume its normal brightness after a few seconds to confirm the
adjustment.
4.2.2 Preset Mode
In this mode, the Rear Control light is ON to indicate panel voltage and current
controls are deactivated.
There are three presets P1/P2/P3 on the Recall Selection Switch. The factory preset
values are shown in Table 3.
The user can also set custom output voltage and current using Set Mode. Please refer
to Section 4.2.4 for details.

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Recall No.
Output Voltage
Output Current
P1
5 V
Maximum
P2
13.8 V
Maximum
P3
Model 1685B: 55 V
Model 1687B: 25 V
Model 1688B: 15 V
Maximum
Table 3 - Default Presets
4.2.3 Analog Remote Control Mode
Select this mode to control the output voltage and current via remote control
connector. Please refer to Section 5.1 for more details.
4.2.4 Set Mode
First, enter Set Mode by pushing Mode Selection Switch to “Set”position.
To define the preset output P1/P2/P3
1. Select the Recall Switch to the position you want to set: P1, P2, or P3.
2. Adjust the front panel voltage control knob to set your desired voltage
value.
3. Adjust the front panel current control knob to set your desired current limit
value.
4. Repeat the procedure for remaining presets P1, P2, or P3 if desired.
5. Move Mode Selection Switch from “Set”to “Preset”position to confirm your
settings.

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To reset presets to factory settings
1. Press and hold the Voltage Control Knob for 30s to enter Menu mode.
2. When it is showing “CCO”, rotate the Voltage Control Knob until voltage
meter shows “rPr”.
3. Then rotate the Current Control Knob until the current meter shows “YES”.
4. Press the Current Control Knob once to confirm. The “YES” will light up after
successfully resetting presets to factory default values.

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5. Finally, press the Voltage Control Knob to exit.
Note:
All the set values in the presets will be saved even after the power supply
has been turned off.
Always check output voltage of Presets before connecting to load.
To check the preset values, move Mode Selection Switch to “Preset”
position.
Move the Recall Switch to P1, P2, or P3.
The voltage and current settings of corresponding presets P1, P2, or P3 will
be shown on the panel meters.
5 Remote Control
There are two methods to remotely control voltage and current.
Note: Both methods require the remote control connector plug to be set up in order
for analog remote control mode to be functional; otherwise the unit will be in CC
mode all the time.
5.1 Analog Remote Control
Set up the provided remote connector plug.
(a) Remove the black portion of the remote control connector plug by removing
the screw as shown in Figure 4.