B+K precision 9120 User manual

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

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Table of contents
General Information ……………………………………………. 3
Features …………………………………………………..……… 5
Local Mode Operation………………….……………………….. 7
Front panel description ……………………………………………. 7
Memory key ………………………………………………………. 7
Storing states in front panel mode ………………………………… 10
Recall key …………………………………………………………. 12
Recalling states in front panel mode ……………………………… 14
Limit key ………………………………………………………….. 15
Modes of operation ……………………………………………….. 16
Constant current operation ………………………………………... 18
Constant voltage operation ………………………………………... 20
On / Off key ……………………………………………………….. 22
Remote / Local key ………………………………………………... 23
Errors / Calibrate key ………………………………………………25
Calibration Overview……………………………………………. 28
Calibration security code ……………………………………...... 28
Unsecure procedure for calibration …………………………….… 29
Hardware unsecure procedure for calibration ……………………. 32
Calibration Procedure …………………………………………… 34
Voltage Calibration Procedure ……………………………………. 35
Volt Zero Scale Calibration ……………………………………….. 35
Volt Full Gain Calibration ………………………………………... 36
OVP Calibration …………………………………………………… 37
Current Calibration Procedure …………………………………….. 38
Current Zero Scale Calibration ……………………………………. 38
Current Full Gain Calibration …………………………………….. 39
OVP / Secure key ………………………………………………….. 41
Programming OVP in front panel mode …………………………. 44
Clearing OVP condition …………………………………………… 46
Rear panel description ……………………………………………… 50
Remote Interface ……………………………………..………….. 51
SCPI Commands …………………………………………………. 52
SCPI Commands Overview ………………………………………. 54
DISPlay Subsystem ……………………………………………….. 54

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Table of contents
OUTPut Subsystem ………………………………………………… 55
SYSTem Subsystem ……………………………………………….. 55
SOURce Subsystem ……………………………………………….. 56
MEASure Subsystem ………………………………………………. 62
TRIGger Subsystem ………………………………………………… 63
Non_SCPI commands ………………………………………………. 67
IEEE 488.2 commands ……………………………………………... 68
SCPI Status Registers ……………………………………………….. 70
Error Messages …………………………………………………… 74
Command Errors …………………………………………………… 74
Execution Errors …………………………………………………… 76
Device-specific Errors ……………………………………………... 76
Self-test Errors …………………………………………………….. 77
Calibration Errors …………………………………………………. 79
Technical Specifications ……………………………………….… 82
Supplemental Characteristics ……………………………………… 86
Programming Ranges ………………………………………………. 88
Reset Values ………………………………………………………... 89
Interface Cable ……………………………………………………… 90
Warranty Information ……………………………………….… 91
Service Information ………………………………………….… 93

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
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
The power supply can be locally or remote controlled.
Interfaces: RS232 (Standard)
The commands available in remote interface mode are
•SCPI (Standard Commands for Programmable Instruments) commands
(SCPI 99 standard)

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5
Features
•Constant Voltage / Constant Current modes of operation
This power supply can operate in either constant voltage or constant current
modes. The passingfrom 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 circuitcan 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.

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Local mode operation
Front panel keys 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 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. The state will be identified using location number in
non-volatile memory and the default name.
By pressing Memory key, state number and state name 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 the current 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.
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.
Store State
Name State

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By pressing Memory key again, state name can be set.
Important note!
A state name must be set here, or the state will not be saved.
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 name is set, you press Memory again and
the current state is stored in the selected location of the non-volatile
memory. Done message will be displayed.
Important note!
Store State option will store the parameters of current operation state and will
not set a name for the stored state.
NameState option will set a name for the the state to be saved.
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 details, see SCPI
Commands section)
The rest of the parameters can be set both 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 pressingMemory key again.
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 for the stored state.
The saving action is realized by pressing Memory key. After that, Done
message will be displayed.
Store State
Name State
Exit

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and 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 will set a name for the the state to be saved.
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 without any notification from the power
supply.
Done

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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 details see Reset Values section).
After powerup, 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. (see 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 and turning the knob all operating states stored in non-
volatile memory are displayed. An operating state is selected 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 limit mode, > < 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.

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Constant current operation
In constant current operation, current values inlimit mode and normal mode are
the same, but voltage values are not.
To set the power supply in constant current operation, you must follow the
steps described bellow:
1. Select the limit values for voltage and current parameters (Ulim and
Ilim), depending on the application
2. Calculate resistor’s value Rload.
Using Ohm’s law, calculate the resistor’s value that allows the power supply to
go in constant current mode of operation.
3. Turn on the power supply and set limit mode operation
Press Limit key to setlimit mode.
Now the power supply displays limit values for voltage and current. lmt
indicator is displayed, too. (it will be displayed until you go tonormal mode).
4. Set voltage and current limit values
Limit values must be chosen so the following conditions are respected:
Ulim > Ilim ·Rload ,so Ulim < Uout
Ilim < Iout
Voltage and current limit valuesare set using:
Volt / Amp key to select current value,
> < keys to select the digit to adjust (selected digit has cursor underneath it)
knob to set the digit to desired value
5. Set normal mode operation
You can set normal mode operation by pressing Limit key or let the display
time-out (after several seconds with no action, power supply returns to normal
mode operation).
6. Disable the output of the power supply
By pressing On / Off key, the output of the power supply can be disabled.
7. Connect Rload resistor to the output terminals
Rload resistor is connected between (-) and (+) terminals of the power supply.

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8. Enable the output of the power supply
By pressing On / Off key, you enable the output.
Power supply goes to normal mode operation and CC indicator will be
displayed. In this case constant current operation is active.
If CV indicator will be displayed, you must set a higher value for voltage limit.
Important note!
By turning the knob, voltage and current limit values can be adjusted.
The adjustion of the voltage limit value can be seen only inlimit mode.
The adjustion of the current limit value can be seen in both limit mode and
normal mode.
Important note!
Constant current operation can be used depending on the application.
It is very useful to protect the circuitry connected to the power supply from
accidently increases of current value.