B+K precision 1739 User manual

Model 1739
DC Power Supply with 0.1mA Settable
Resolution
INSTRUCTION MANUAL

1
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.

2
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
Connect to safety earth ground using the wire recommended in the user
manual.
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
1Safety Summary............................................................. 1
2Introduction.................................................................... 5
3Quick Reference............................................................. 7
3.1 Front Panel......................................................................................... 7
3.2 Rear Panel.......................................................................................... 8
4Operating Instructions.................................................. 9
4.1 Instrument Hook-Up........................................................................ 10
4.2 Typical Constant Voltage Operation................................................ 12
4.3 Setting Current Limit....................................................................... 13
4.4 Typical Constant Current Operation................................................ 14
4.5 Constant Voltage/Constant Current Characteristic .......................... 15
4.6 Saving the Power Supply’s Current State........................................ 16
4.7 Connecting Two Power Supplies in Series...................................... 16
4.8 Connecting Two Power Supplies in Parallel.................................... 17
5RS232 Interface............................................................ 18
5.1 RS232 Configuration Overview...................................................... 19
5.2 RS232 Commands........................................................................... 19
6Maintenance ................................................................. 21
6.1 Fuse Replacement............................................................................ 21
6.2 Adjustments..................................................................................... 21
6.3 Calibration....................................................................................... 22
6.4 Instrument Repair Service ............................................................... 27
7Error Messages............................................................. 27
7.1 Self-Test Errors................................................................................ 27
7.2 Calibration Errors............................................................................ 27
7.3 Command Errors.............................................................................. 29
8Specifications................................................................ 29
9Service Information..................................................... 31
10 Limited Three-Year Warranty................................... 32

5
2 Introduction
Description
The B&K Precision model 1739 is a high quality, low current DC power source.
This power supply provides 0-30 volts dc output, adjustable with both coarse and
fine voltage controls for precise settability. The current output is 0-1 amps,
adjustable with both coarse and fine current controls. Two large LED meters
continuously monitor the output voltage and current. The VOLTAGE meter is
green, while the CURRENT meter is red.
The power supply can be programmed locally from the front panel or remotely
through the RS-232 interface. Two large LED meters continuously monitor the
output voltage and current. The voltage meter is green, while the current meter
is red. The power supply can be operated locally from the front panel or
remotely through the RS-232 interface.
The 1739 exhibits excellent regulation and low ripple characteristics. The circuit
design incorporates a pre-regulator, which greatly reduces internal power
dissipation at low output voltages. The styling is both attractive and functional.
The mechanical configuration conserves bench space and allows for easy
portability.
This instrument may be used in constant voltage or constant current
applications. The crossover from constant voltage to constant current modes is
smooth and automatic. LEDs indicate the “CV” (constant voltage) or “CC”
(constant current) mode of operation. In constant voltage applications, a current
limit may be preset. When load variations cause the current to reach the preset
limit, the unit then regulates output current rather than output voltage.
Current limits are adjustable from 1.0 mA to maximum, in as little as 0.1 mA
steps. In constant current applications, the maximum voltage may be preset.
When load variations cause current to drop below the regulated value, the unit
reverts to regulated voltage operation at the preset value.

6
Reverse polarity protection prevents accidental damage to the power supply
from improper connection to an external device, and current limiting protects
the equipment being powered, as well as the power supply.
The output is isolated from chassis and earth ground, which permits full flexibility
of connections. When needed, the (+) or (-) polarity may be strapped to ground,
or either polarity may be floated to an external voltage. Two supplies may be
connected in series as a 0-to-60 V power source, or two supplies may be
connected in parallel for up to twice the output current.
This power supply is well suited for a wide variety of electrical and electronics
applications in service shops, engineering labs, production testing, school
laboratories, and home use by hobbyists, where precise levels of low current are
required, including 4-20 mA loop testing and calibration or simple IC testing.
Features
•Low 1 mA settable current limit with 0.1 mA resolution
•Output on/off button
•Low ripple and noise
•Excellent regulation
•Constant voltage (CV) and constant current (CC) operation
•Two large, easy-to-read LED displays provide good visibility in bright or low
light
•LED indication for CV and CC modes
•Saved programmed values upon power-up
•RS-232 interface
•Pre-regulator for limiting internal dissipation for higher reliability
•Isolated output
•Overload protection
•Reverse polarity protection
•Power-on self test
•Modern functional configuration conserves bench space and aids
portability

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3 Quick Reference
3.1 Front Panel
Figure 1 - Front Panel
INDICATORS
Either the CV or CC LED indicators will be lit whenever the unit is operating. The unit
automatically changes from CV to CC operation when the preset current limit is
reached.
1) CV (Constant Voltage) Indicator. The green LED is lit in constant voltage mode.
Unit regulates output voltage at the value set by voltage controls.
2) CC (Constant Current) Indicator. The red LED is lit in constant current mode. Unit
regulates output current at the value set by current controls.
3) Green LED Display. 4-digit display continuously monitors voltage.
4) Red LED Display. 4-digit display continuously monitors current.
VOLTAGE CONTROLS
5) Voltage Coarse Control. Coarse adjustment of output voltage. Read value on the
green LED display.
6) Voltage Fine Control. Fine adjustment of output voltage. Read value on the
green LED display.
7
8
6
5
9
1
2
3
4
10
11
12
13

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CURRENT CONTROL
7) Current Coarse Control. Adjusts current limit in constant voltage mode. Adjusts
constant current value in constant current mode. Current can be read from the
red LED display.
8) Current Fine Control. Adjusts current limit in constant voltage mode. Adjusts
constant current value in constant current mode. Current can be read from the
red LED display.
POWER CONTROLS
9) Power ON-OFF Switch.
OUTPUT TERMINALS & CONTROL
10) “-” Terminal (Black). Negative polarity output terminal.
11) GND Terminal. Earth and chassis ground.
12) “+” Terminal (Red). Positive polarity output terminal.
13) Output On/Off button. Turns output power on or off without powering down the
entire instrument.
3.2 Rear Panel
Figure 2 - Rear Panel
13) Power Cord
14) Fuse
15) RS-232 Interface Connector
15
14
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4 Operating Instructions
Safety Precautions
Use only a polarized 3-wire AC outlet. This assures that the power supply chassis,
case, and ground terminal are connected to a good earth ground and reduces
danger from electrical shock.
There is little danger of electrical shock from the power supply output, which
produces a maximum of 30 volts dc. However, there may be great danger of
electrical shock if the power supply output is connected to an external high
voltage. Some equipment being powered may contain high voltage and present a
shock hazard. Observe caution. If the power supply output is floated (referenced
to a voltage rather than earth ground) turn off the power supply and the
equipment under test when making connections. Never float the power supply to
a potential greater than 100 volts peak with respect to earth ground.
Equipment Precautions
Avoid using the power supply in ambient temperatures above +40° C. Always
allow sufficient air space around the heat sink at the rear of the power supply for
effective radiation to prevent internal heat build-up.
Although the power supply is protected against reverse polarity damage, the
circuit being powered may not include such protection. Always carefully observe
polarity; incorrect polarity may damage the equipment under test.
Do not exceed the voltage rating of the circuit being powered. Many transistors
and integrated circuits will not withstand voltage of 30 volts.
There is no need to worry about voltage spikes or overshoot damaging the
equipment under test. The voltage between the output terminals of the power
supply never exceeds the preset value as the POWER switch is turned on or off.

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4.1 Instrument Hook-Up
1. Turn off the power supply and the equipment to be powered during hook-
up.
2. Connect the positive polarity of the device being powered to the red (+)
terminal of the power supply.
3. Connect the negative polarity of the device being powered to the black (-)
terminal of the power supply.
4. Figure 3illustrates the grounding possibilities.
a. If the negative polarity of the equipment or circuit being powered is also
the chassis or common, it may be grounded to earth by strapping the black
(-) terminal to the green ( ) terminal as shown in Figure 3A.
b.Similarly, the positive polarity can be grounded by strapping the red (+)
terminal to the green ( ) terminal as shown in Figure 3B.
c. If an earth ground reference is not required, the configuration of Figure 3C
may be used. The scheme in Figure 3C should also be used where it is not
known whether the chassis is common with either the positive or negative
polarity.
d.If the chassis or common of the equipment being powered is separate
from both the positive and negative polarity power inputs, use the
connection shown in Figure 3D.
6. Observe proper polarity. If the circuit being powered is not equipped with
reverse polarity protection, damage to the circuit can result from reverse
polarity. Use color coded hook-up leads, for convenience in identifying
polarity, red for (+) and black for (-).
7. Make sure that the hook-up leads offer sufficient current capability and low
resistance between the power supply and the circuits being powered.

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Figure 3 (A and B) - Grounding Possibilities
Figure 3 (C and D) - Grounding Possibilities

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4.2 Typical Constant Voltage Operation
1. Before connecting the device to be powered to the power supply, determine
the maximum safe load current for the device to be powered and set the
current limit value (see Setting Current Limit procedure in this section).
2. The output voltage can be set using the voltage coarse knob (with a 1V
resolution) and voltage fine knob (with a 10 mV resolution). After the last
adjustment you must wait 3 seconds until the state is saved.
3. Turn off power supply and connect it to the device to be powered (see
Instrument Hook-Up procedure in this section).
4. Turn on the power switch. The CV indicator should light.
5. Increase the voltage setting until the voltage LED display reads the desired
value. The fine control permits easier setting to a specific value.
6. Note the load current on the current LED display.
7. If the load current exceeds the preset current limit, the CV indicator will go
off and the CC indicator will light. In this case, the power supply
automatically switches to the constant current mode, and further rotation of
the voltage control will not increase the output voltage.
Figure 4 - Typical Constant Voltage Operation

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4.3 Setting Current Limit
1. Determine the maximum safe current for the device to be powered.
2. Temporarily short the (+) and (-) terminals of the power supply together
with a test lead.
3. Adjust the coarse and fine current control for the desired current limit. Read
the current value on the current LED display.
4. The current limit (overload protection) has now been preset. Do not change
the current controls settings after this step.
5. Remove the short between the (+) and (-) terminals and hook up for constant
voltage operation.
Figure 5 - Setting Current Limit

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4.4 Typical Constant Current Operation
1. Before connecting the device to be powered to the power supply, determine the
maximum safe voltage to be applied, and set the voltage controls to obtain that
voltage reading on the voltage LED display.
2. Determine the desired constant current value.
3. Set the coarse and fine current control to minimum (1mA). Wait 3 seconds.
4. Turn off the power supplies output and connect it to the device to be powered.
5. Turn on the power supplies output. The CC indicator should light.
6. Increase the coarse and fine current control setting until the desired constant
current value is read on the display, or set the current limit in advance (before
connecting the load) as described earlier in the Setting Current Limit procedure.
7. If the load current drops below the constant current value, the CC indicator will go
off and the CV indicator will light. In this case, the power supply automatically
switches to the constant voltage mode, and further rotation of the current
controls will not increase the output current.
Figure 6 - Typical Constant Current Operation

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4.5 Constant Voltage/Constant Current Characteristic
The working characteristic of this power supply is called a constant voltage/constant
current automatic crossover type. This permits continuous transition from constant
current to constant voltage modes in response to the load change. The intersection
of constant voltage and constant current modes is called the crossover point. Figure
7shows the relationship between this crossover point and the load.
For example, if the load is such that the power supply is operating in the constant
voltage mode, a regulated output voltage is provided. The output voltage remains
constant as the load decreases, up until the point where the preset current limit is
reached. At that point, the output current becomes constant and the output voltage
drops in proportion to further decreases in load. The crossover point is indicated by
the front panel LED indicators. The crossover point is reached when the CV indicator
goes off and the CC indicator comes on.
Similarly, crossover from the constant current to the constant voltage mode
automatically occurs from an increase in load. A good example of this would be seen
when charging a 12-volt battery. Initially, the open circuit voltage of the power
supply may be preset for 13.8 volts. A low battery will have a low load on the supply
and it will operate in the constant current mode, which may be adjusted for a 1 amp
charging rate. As the battery becomes charged, and its voltage approaches 13.8 volts,
its load increases to the point where it no longer demands the full 1 amp charging
rate. This is the crossover point where the power supply goes into the constant
voltage mode.
Figure 7 - Constant Voltage/Constant Current Characteristic

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4.6 Saving the Power Supply’s Current State
The current state of the power supply is saved after 2 seconds from the last
adjustment or after the “SAVE” command is received through the RS232 interface.
4.7 Connecting Two Power Supplies in Series
Two power supplies may be connected in series to provide a variable 0-60 volt
output. In this configuration, the two power supplies can supply up to 60V-1A. See
Figure 8for the connection scheme.
When connected in series, the voltage controls of each power supply exercise control
over a 0-30 volt range. Add the LED display readings together or connect an external
voltmeter across the load to determine the total output voltage.
Load current may be monitored from either supply; the readings will be identical
since they are connected in series. Also, since the supplies are connected in series, it
is only necessary to set the current limit on one of the supplies; the other may be set
for maximum.
Figure 8 - Connecting Two Power Supplies in Series

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4.8 Connecting Two Power Supplies in Parallel
Two power supplies may be connected in parallel to double the maximum load
current. In this configuration, the two power supplies will provide 0-30 volt
output at up to 2 amps. Current equalizing resistors must be used as shown in
Figure 9. However, the protective current limiting feature will prevent damage if
current is temporarily unbalanced during set-up.
When connected in parallel and operating in the constant voltage mode,
determine the total load current limit and preset the current limiting for each
power supply to half the total load current value. Then when the load is
connected, set the voltage controls on the two power supplies for equal voltage
readings. This should also provide approximately equal current from each supply.
Add the two current meter readings together for total load current, or connect
an external ammeter in series with the load.
Figure 9 - Connecting Two Power Supplies in Parallel

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If the current equalizing resistors are not well matched, it is preferable that the
voltages be slightly unbalanced to achieve current balance. Be sure that the
supplies are adequately balanced so that both remain in the CV mode.
When connected in parallel and operating in the constant current mode, the
voltage controls of both supplies should be preset to the same value. Then when
the load is connected, the current controls of the two supplies should be
adjusted for approximately equal current from each unit. Be sure that both
supplies remain in the CC mode.
5 RS232 Interface
The power supply can be connected to the RS232 interface using the 9-pin (DB-9)
serial connector on the rear panel. The 1739 uses a null modem RS232 cable. The
cable pin diagram for the DB-9 connector is shown in the picture below:
2
3
5
RX
TX
GND
DB-9
connector
Instrument
2
3
5
RX
TX
GND
PC
DB-9
connector
Figure 10 - RS232 Cable Pin Diagram
For all communications over the RS232 interface, the power supply uses Xon/Xoff
protocol.
NOTE:If using HyperTerminal, make sure you properly configure the “ASCII Setup”. In
“ASCII Setup”, do not append line feeds to “ASCII Sending”. “Echo typed characters
locally” can be checked, but “Send line ends with line feeds” should be left
unchecked. In “ASCII Receiving”, “Append line feeds to incoming line ends” can also
be checked.