B+K precision 9120 User manual

Instruction Manual
Model 9120, 9121, 9122 & 9123
SINGLE OUTPUT PROGRAMMABLE DC POWER SUPPLY

1
Table of contents
General Information ……………………………………………. 5
Features …………………………………………………..……… 7
Local Mode Operation………………….……………………….. 9
Front Panel Description ……………………………………………. 9
Memory Key ………………………………………………………. 9
Storing States in Front Panel Mode ………………………………… 12
Recall Key …………………………………………………………. 14
Recalling States in Front Panel Mode ……………………………… 16
Limit Key ………………………………………………………….. 17
Modes of Operation ……………………………………………….. 18
Constant Current Operation ………………………………………... 20
Constant Voltage Operation ………………………………………... 22
On / Off Key ……………………………………………………….. 24
Remote / Local Key ………………………………………………... 25
Local Mode Function ……………………………………………… 25
Remote Interface Configuration …………………………………… 25
RS-232 Configuration ……………………………………………... 27
GPIB / 488 Configuration …………………………………………. 28
Remote Mode and Indicators ……………………………………… 29
Errors / Calibrate key ………………………………………………30
Calibration Overview ……………………………………………. 33
Calibration Security Code ……………………………………...... 33
Unsecure Procedure for Calibration …………………………….… 34
Hardware Unsecure Procedure for Calibration ……………………. 37
Calibration Procedure …………………………………………… 39
Voltage Calibration Procedure ……………………………………. 40
Volt Zero Scale Calibration ……………………………………….. 40
Volt Full Gain Calibration ………………………………………... 41
OVP Calibration …………………………………………………… 42
Current Calibration Procedure …………………………………….. 43
Current Zero Scale Calibration ……………………………………. 43
Current Full Gain Calibration …………………………………….. 44
OVP / Secure Key ………………………………………………….. 46
Programming OVP in Front Panel Mode …………………………. 49
Clearing Overvoltage Condition …………………………………… 50
Rear Panel Description ……………………………………………… 54

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Table of contents
Remote Interface ……………………………………..………….. 55
RS-232 Interface …………………………………………………... 55
GPIB / 488 Interface ………………………………………………. 56
Functional Description of GPIB / 488 Interface ………………….. 57
IEEE 488 Addressing ……………………………………………... 58
Bus Description ……………………………………………………. 59
Sending Commands Over GPIB Remote Interface ……………….. 61
Serial Poll Procedure ……………………………………………… 62
Interrogative Commands Over GPIB Interface …………………… 62
Commands Sent Over Remote Interface ………………………….. 63
Introduction to SCPI Language …………………………………… 64
SCPI Commands Overview ………………………………………. 69
DISPlay Subsystem ……………………………………………….. 69
MEASure Subsystem ………………………………………………. 70
MEMory Subsystem ………………………………………………... 71
OUTPut Subsystem ………………………………………………… 72
SOURce Subsystem ……………………………………………….. 73
STATus Subsystem ………………………………………………… 80
SYSTem Subsystem ……………………………………………….. 81
TRIGger Subsystem ……………………………………………….. 82
Non_SCPIcommands ………………………………………………. 86
IEEE 488.2 commands ……………………………………………... 87
IEEE 488 Bus Commands …………………………………………. 89
ASCII Table for GPIB ……………………………………………… 91
SCPI Status Registers ……………………………………………….. 93
Error Messages …………………………………………………… 97
Command Errors …………………………………………………… 97
Execution Errors …………………………………………………… 99
Device Specific Errors ……………………………………………... 99
Self-test Errors …………………………………………………….. 100
Calibration Errors …………………………………………………. 102

3
Table of contents
Technical Specifications ……………………………………….… 105
Supplemental Characteristics ……………………………………… 110
Programming Ranges ………………………………………………. 112
Reset Values ………………………………………………………... 113
InterfaceCable ……………………………………………………… 114
Warranty Information ……………………………………….… 115
Service Information ………………………………………….… 117

5
General Information
Single output programmable DC power supplies.
Output voltage is: 0 to 30.0V for Model 9120
0 to 20.0V for Model 9121
0 to 60.0 V for Model 9122
0 to 30.0 V for Model 9123
Output current is: 0 to 3.00A for Model 9120
0 to 5.00 A for Model 9121
0 to 2.50 A for Model 9122
0 to 5.00 A for Model 9123
The power supply can be locally or remote controlled.
Available interfaces for 912x power supply models:
9120 9121 9122 9123
RS-232 Standard Standard Standard Standard
GPIB / 488 Optional Optional Optional Standard
The commands available in remote interface mode are
•SCPI (Standard Commands for Programmable Instruments) commands
(1999 SCPI standard)
•IEEE 488.2 commands
•IEEE 488 bus commands (only for GPIB / 488 interface)

6

7
Features
•Constant Voltage / Constant Current modes of operation
This power supply can operate in either constant voltage or constant current
modes. The passing from one mode of operation to another is automatic.
The active mode of operation is indicated using two indicators:
CV –constant voltage mode of operation
CC –constant current mode of operation
•Overvoltage protection
Overvoltage protection circuit can be locally or remote activated.
When it is active, ovp indicator is displayed.
•Output on / off
When output off, output voltage is 0 V.
This permits a zero output voltage without switching off the power supply.
•100 operating states storage
States are identified by location number and name.
Stored parameters are: voltage limit, voltage step, overvoltage protection level,
state of overvoltage protection circuit, current limit, current step, voltage trigger
value, current trigger value, trigger delay value, trigger source, stored state
name, state of display, output state.
After power on, state 0, named power_up will become the current operating
state.
•error messages
Errors are stored in a 20 locations FIFO (first in first out) queue.
They can be read in local mode (error number returned) or in remote operation
mode (error number and definition returned).
Every error is announced by a beep and the err indicator.

8

9
Local mode operation
Front Panel Description
Memory Key
Note: Memory location 00 is the power_up state. When the unit is powered up,
the power supply will set itself to the settings stored in location 00.
Note: If you press the Recall button while turning the power on,the power
supply will power up using memory location 01 parameters.
This button is used to store power supply’s current operating state in non-
volatile memory. Using this function all operating parameters are saved so they
can be recalled. You can store 100 different operating states (numbered from 0
to 99) in the non-volatile memory.
Stored parameters are: voltage limit, voltage step, overvoltage protection level,
state of overvoltage protection circuit, current limit, current step, voltage trigger
value, current trigger value, trigger delay value, trigger source, stored state
name, state of display, output state.
By pressing Memory key, you enter in Memory menu.
By turning the knob following options will be displayed:
Store State
Name State
Exit

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Options are selected by pressing Memory key when the desired option is
displayed.
Memory Menu Overview
Store State option will store the current operating state without setting a
name for this state.
By pressing Memorykey, state number and state name (if you set one)are
displayed in ascending order by turning the knob.
In this menu,Exit option is available, too. In this case, you leave the store
operation mode, without changing anything. No Change message will be
displayed and the power supply returns to the previous state (the state
before entering Memory menu).
The states are scrolled using the knob.
A location is selected by pressing Memory key. If the location you choose
is already written, it is overwritten (without any warning) with the current
state parameters, but the name (the set one or the default one remains
unchanged). Done message will be displayed.
Name State option allows you to set a name for selected state (you can also
change a name set before).
The state name can have up to 10 charatcters. The default name is 10 blank
characters.
By pressing Memorykey, state number of non-volatile memory locations is
displayed in ascending order by turning the knob.
By pressing Memory key again, state name can be set.
When setting the name, selected digit has the cursor underneath it.
Characters of the name are selected by rotating the knob. When desired
ASCII character is displayed, you can pass to another digit selection using >
< cursor position keys. When the desired name is set, you press Memory
again and the state name is stored in the selected location of the non-volatile
memory. Done message will be displayed.
Store State
Name State

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In this menu Exit option is available, too. In this case, you leave the store
operation mode, without changing the name for any state. No Change
message will be displayed and the power supply returns to the previous state
(the state before entering Memory menu).
Important note!
Store State option will store the parameters of current operation state in the
selected location and will not set a name for the stored state.
NameState option will set a name for the selected state.
Exit option allows you to leave the store operation mode, without changing
anything. No Change message will be displayed and the power supply
returns to the previous state (the state before entering Memory menu).
Important note!
If you enter in the Memory menu and no action takes place for approx. 20
seconds, the power supply leaves the Memory menu. No Change message is
displayed and the power supply returns to the previous state (the state before
entering Memory menu).
Exit

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Storing States in Front Panel Mode
To store an operating state in front panel mode you must follow the steps
described bellow:
1. Set the power supply in the desired operating state
Stored parameters are: voltage limit, voltage step, overvoltage protection level,
state of overvoltage protection circuit, current limit, current step, voltage trigger
value, current trigger value, trigger delay value, trigger source, stored state
name, state of display, output state.
Voltage step, current step, voltage trigger value, current trigger value, trigger
delay value, trigger source and state of display parameters can be set only over
the remote interface, using SCPI commands (for more information, please refer
to SCPI Commands section).
The rest of the parameters can be set either from the front panel,or over the
remote interface.
2. Enter the Memory menu
By pressing Memory key, you enter Memory menu.
By turning the knob, following options are displayed:
Options are selected by pressing Memory key when desired option is
displayed.
3. Select StoreState option
When Store State or Name State options are selected, state number and state
name (if available) of non-volatile memory locations are displayed in ascending
order, by turning the knob.
If Store State option is selected, the stored operating state has the default
name, if none set before.
Store State option will store the parameters of current operation state and will
not set a name (or will not change it, if the name was set before) for the stored
state.
Store State
Name State
Exit

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The saving action is realized by pressing Memory key. After that, Done
message will be displayedand the power supply returns to normal mode.
4. Select Name State option
In order to select this option , Memory key must be pressed again.
NameState option allows you to set a name for the selected state.
The saving action is realized by pressing Memory key. After that, Done
message will be displayed.
Important note!
The power supply allows 100 states to be stored. When shipped, the power
supply has power_up state stored and all the other locations are empty.
The stored states are kept in a non-volatile memory, so they won’t be lost when
the power supply is turned off.
A state location can be overwritten (both name and parameters) without any
notification from the power supply.
Done

14
Recall Key
This key is used to recall an operating state from the storage locations in non-
volatile memory. You can recall any operating state from 100 different
operating states stored in the non-volatile memory. The recalled state becomes
the current operating state.
By pressing Recall key, you enter in Recall menu.
By turning the knob,following options will be displayed:
etc. (all 100 operating states are displayed)
Options are selected by pressing Recall key when the desired option is
displayed.
Recalling action is terminated by pressing Recall key. After that, Done
message will be displayed.
Recall Menu Overview
When a state option is selected, the stored state recalled becomes the current
operating state of the power supply.
Recalled parameters are: voltage limit, voltage step, overvoltage protection
level, state of overvoltage protection circuit, current limit, current step,
voltage trigger value, current trigger value, trigger delay value, trigger
source, stored state name, state of display, output state.
01:
Exit
Reset
02: Test_mode
01: State 1
00: power_up

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Exit option allows you to leave the Recall menu, without changing
anything. No Change message will be displayed and the power supply
returns to the previous state (the state before enteringRecall menu).
Reset option allows you to reset the power supply without switching off
(for more information, please refer to Reset Values section).
After power up, the power supply recalls state 0.
When delivered, power_upstate has the following parameters:
Ulim = 1 V
Ilim = maximum available current value (see Programing ranges
table, in the Techincal Specifications section)
OVP trip level = maximum programmable value (see Programing
ranges table, in the Techincal Specifications section)
Output state on
The rest of the parameters have the default value after reset. (please refer to
Reset values table, in the Techincal Specifications section)
For this operating state, Name State option is not available (so the state
name cannot be changed), but Store State option is available (so the user
can save the desired state for power up).
Important note!
If you enter Recall menu and no action takes place for approx. 20 seconds, the
power supply leaves the Recall menu. No Change message is displayed and
the power supply returns to the previous state (the state before entering Recall
menu).
Exit
Reset
00: power_up

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Recalling States in Front Panel Mode
To recall an operating state in front panel mode,you must follow the steps
described bellow:
1. Enter the Recall menu
By pressing Recall key, you enter the Recall menu.
By turning the knob, following options are displayed:
etc. (all 100 operating states are displayed)
2. Select the operating state
By using < > keys (to select the digit you modify by turning the knob) and
turning the knob all operating states stored in non-volatile memory are
displayed. An operating state is recalled by pressing Recall key when desired
state is displayed.
3. Recall the operating state
When Recall key is pressed, the selected operating state becomes the current
operating state of the power supply, after Done message is displayed.
01: State 1
Exit
Reset
02: Test_mode

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Limit Key
The power supply works in 2 modes:
ØØ Limit mode
ØØ Normal mode
In limit mode limit values of voltage and current are displayed. These are the
programmed values (from the front panel or over the remote interface).
Limit key is used to get the power supply to limit mode. In this mode, lmt
indicator and limit values for voltage and current will be displayed.
In limit mode, limit values can be adjusted by turning the knob. To adjust
values in limitmode, > < keys must be used to select the digit you want to
adjust. The selected digit has the cursor underneath it. To increase / decrease
value of digit, knob must be turned.
After setting the limit values, by pressing Limitkey, the power supply returns
to normal mode. It also returns to normal mode after several seconds (display
time-out) with no action.
In normal mode, voltage and current values measured at the output terminals of
the power supply are displayed.
When you turn on the power supply, the cursor is placed underneath the voltage
value (units digit). To pass from voltage value to current value Volt/Amp key
must be used. This key toggles between voltage value and current value.

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Modes of Operation
Depending on the application, the power supply can be used as a constant
current source or as a constant voltage source.
In order to understand constant current and constant voltage operation, a
numeric example will be used.
Uout R
Let’s consider a resistor connected to the output terminals of the power supply
(R resistor).
Limit (programmed) values are:
Ulim=5V
Ilim =2A
Uout and Iout are the voltage and current valuesmeasured at the output
terminals of the power supply.
Depending on the resistor value, the power supply will pass from one mode of
operation to another
R (Ù) Uout (V) Iout (A) Mode of
operation
10 50.5 CV
551CV
122CC
In constant voltage mode, programmed voltage value is equal with the voltage
value measured at the output terminals of the power supply. (Uout = Ulim).
Using Ohm’s law, depending on the resistor’s value, output current value can
be calculated and it is smaller than current limit value (see first and second
rows of the table).
The power supply will remain in CV operation as long as the limit current
value is greater than output current value.

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When the resistor’s value decreases so the output current value becomes equal
to the current limit value, power supply will go to constant current operation
(see third row of the table).
If the resistor value is R = 1 Ù, for Uout = 5V, using Ohm’s law the output
current is 5A. But this value is greater than current limit value, so the power
supply limits the output current to the limit programmed value. That is why in
the third row of the table Iout = 2 A. In this case, Uout is changed, too. Using
Ohm’s law again, the output voltage is calculated using output current value
and the resistor value, so it is 2 V.
So the power supply will go to constant current operation when the output
current value becomes equal or greater than the limit value.
When the output current value becomes smaller than the limit value (by
changing resistor’s value), the power supply will go back to constant voltage
operation.
In conclusion:
CV: Uout = Ulim and Iout < Ilim
CC: Uout < Ulim and Iout = Ilim
The following section will explain how to get the power supply in constant
current operation mode and in constant voltage operation mode.