BK Precision 9120, 9123, 9121 Instruction Manual

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Instruction Manual

Model 9120, 9121, 9122 & 9123

SINGLE OUTPUT PROGRAMMABLE DC POWER SUPPLY

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

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_SCPI commands ………………………………………………. 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

Table of contents

Technical Specifications ……………………………………….… 105

Supplemental Ch aracteristics ……………………………………… 110 Programming Ranges ………………………………………………. 112

Reset Values ………………………………………………………... 113 Interface Cable ……………………………………………………… 114

Warranty Information ……………………………………….… 115 Service Information ………………………………………….… 117

General Information

Single output programmable DC power supplies.

Output voltage is: 0 to 30.0 V for Model 912 0

0 to 20.0 V for Model 912 1 0 to 60.0 V for Model 9122 0 to 30.0 V for Model 9123

Output current is: 0 to 3.00 A 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)

Features

• Constant Voltage / Constant Current mo des 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.

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 nonvolatile 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

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 Memory key, 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 Memory key, 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

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

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

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

The saving action is realized by pressing Memory key. After that, Done message will be displayed 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 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

Recall Key

This key is used to recall an operating state from the storage locations in nonvolatile 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

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 entering Recall 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_up state has the following parameters:

lim

= 1 V

lim

= 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

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

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 Limit key, 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.

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.

out

Let’s consider a resistor connected to the output terminals of the power supply (R resistor).

Limit (programmed) values are:

lim

=5V

lim

=2A

out

and I

out

are the voltage and current values measured 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) U

out

(V) I

out

(A) Mode of

operation

10 5 0.5 CV

5 5 1 CV 1 2 2 CC

In constant voltage mode, programmed voltage value is equal with the voltage value measured at the output terminals of the power supply. (U

out

= U

lim

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.

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 U

out

= 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 I

out

= 2 A. In this case, U

out

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: U

out

= U

lim

and I

out

< I

lim

CC: U

out

< U

lim

and I

out

= I

lim

The following section will explain how to get the power supply in constant current operation mode and in constant voltage operation mode.

Constant Current Operation

In constant current operation, current values in limit 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 (U

lim

and

lim

), depending on the application

2. Calculate resistor’s value R

load

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 set limit mode. Now the power supply displays limit values for voltage and current. lmt

indicator is displayed, too. (it will be displayed until you go to normal mode).

4. Set voltage and current limit values

Limit values must be chosen so the following conditions are respected:

lim

> I

lim

· R

load

,so

lim

< U

out

lim

< I

out

Voltage and current limit values are 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 R

load

resistor to the output terminals

load

resistor is connected between (-) and (+) terminals of the power supply.

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 in limit 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.

Constant Voltage Operation

In constant voltage operation, voltage values in limit mode and normal mode are the same, but current values are not

To set the power supply in constant voltage operation, you must follow the steps described bellow:

1. Select the limit values for voltage and current parameters (U

lim

and

lim

), depending on the application

2. Calculate resistor’s value R

load

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 set limit mode. Now the power supply displays limit values for voltage and current. lmt

indicator is displayed, too. (it will be displayed until you go to normal mode).

4. Set voltage and current limit values

Limit values must be chosen so the following conditions are respected:

lim

< I

lim

· R

load

,so

lim

< U

out

lim

< I

out

Voltage and current limit values are 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 R

load

resistor to the output terminals

load

resistor is connected between (-) and (+) terminals of the power supply.

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 CV indicator will be

displayed. In this case constant voltage operation is active. If CC indicator will be displayed, you must set a higher value for current limit.

Important note!

By turning the knob, voltage and current limit values can be adjusted. The adjustion of the current limit value can be seen only in limit mode. The adjustion of the voltage limit value can be seen in both limit mode and

normal mode.

On / Off Key

On / Off key is used to enable / disable the output of the power supply from the

front panel. By pressing On / Off key, you alternate these two states: output on / output off.

When the output is off, power supply displays:

The indicators according to power supply’s state will also be displayed (e.g.: ovp, err indicators).

When output off, output voltage is 0 V. So this command permits a zero output voltage without switching off the power supply.

When output off, knob is disabled, to prevent the unwanted changes in voltage and current values. The keys from the front panel are not disabled. You can

also go to limit mode and set limit values for voltage and current. In this case both lmt and off indicators will be displayed.

When output off, by pressing On / Off key, the output is enabled. The power supply will go to normal mode of operation (voltage and current measured values are displayed) or to limit mode of operation (voltage and current limit

values are displayed), depending on the state the power supply was before disabling the output.

The output state of the power supply is one of the parameters stored in nonvolatile memory for each state .

Output off

Remote / Local Key

This key has a double function, depending on the state of the power supply (remote mode or local mode).

Local Mode Function

While in local mode of operation, Remote / Local key has a double function, depending on the state of the power supply.

If the power supply is in calibrating mode, Remote / Local key is used to leave the calibrating mode and return to normal mode of operation (for more

information, please refer to Calibration Overview section)

If the power supply is in limit mode or normal mode of operation, by pressing Remote / Local key, available interfaces are displayed.

Remote Interface Configuration

Available interfaces for 912x power-supply models:

9120 9121 9122 9123 RS-232 Standard Standard Standard Standard

GPIB / 488 Optional Optional Optional Standard

If a power supply has both interfaces implemented, only one interface can be enabled at a time.

Interface selection (and coresponding parameters) is kept in a non-volatile memory, so when powered on, the last selected interface is active.

For a power supply that has both interfaces implemented, when delivered GPIB / 488 interface is selected.

The remote interface can be selected by using front panel or by using a command sent over the interface. Here is described remote interface selection

using front panel keys.

If the power supply is in local mode of operation, by pressing Remote / Local key, selected interface is displayed (RS-232 or GPIB / 488).

By turning the knob, following options will be displayed:

By pressing Remote / Local key once again, the displayed interface is selected and the specific parameters can be set (for RS – 232 interface, baud rate and

parity will be set , for GPIB interface GPIB address of the power supply will be set).

The parameter values can be changed by turning the knob. When desired value for the parameter is displayed, Remote / Local key must be pressed.

Important note! If you enter Remote / Local submenu and no action takes place for approx. 20

seconds, the power supply will leave this submenu. No Change message is displayed and the power supply returns to the previous state (the state before

entering this submenu).

Important note! If you enter Remote / Local submenu and no action takes place for approx. 20 seconds, the power supply will leave this submenu. No Change message is

displayed and the power supply returns to the previous state (the state before entering this submenu).

Important note!

While in local mode, if by pressing Remote / Local key

message will be displayed, it means that the remote interface parameters cannot be read from the non-volatile memory. The power supply must be turned off and then turned on.

If this message is displayed again after pressing Remote / Local key in local mode, the power supply must be delivered to B&K Precision for service.

RS - 232

GPIB / 488

I / O Error

RS-232 Configuration

Available settings for RS-232 interface :

♦ Baud rate: 1200, 2400, 4800, 9600 (factory setting: 9600) ♦ Parity and data bits: None – 8 data bits (factory setting)

Odd – 7 data bits Even – 7 data bits

♦ Number of start bits: 1 bit (cannot be changed) ♦ Number of stop bits: 1 bit (cannot be changed)

Set RS – 232 remote interface parameters

1. Select RS – 232 interface

Press Remote / Local key. If “GPIB / 488” is displa yed, turn the knob until “RS-232” will be displayed.

Press Remote / Local key again. Baud rate settings will be displayed.

2. Select baud rate

By turning the knob, you will view available baud rates: 1200, 2400, 4800, 9600 bits per second.

When desired baud rate is displayed, press Remote / Local key. Parity settings will be displayed.

3. Select parity

By turning the knob, available parities will be displayed:. Even, odd or no parity. Select the desired parity.

By pressing Remote / Local key, the settings will be saved in the non-volatile memory and Saved message will be displayed.

If you didn’t change any of the previous set parameters, the power supply will display No Change message.

If you did change a single parameter from the previous set parameters, Saved message will be displayed. After one of these messages is displayed for several seconds, the power supply

returns to the previous state.

RS - 232

GPIB / 488 Configuration

Available setting for GPIB / 488 interface is address of the power supply.

An IEEE 488 address can take values from 0 to 30.

GPIB address is kept in a non-volatile memory, so when powered on, the last selected address is active.

When supplied from the factory, power supply’s GPIB address is 5.

Set GPIB remote interface parameters

1. Select GPIB / 488 interface

Press Remote / Local key. If “RS-232” is displayed, turn the knob until “GPIB / 488” will be displayed.

Press Remote / Local key again. GPIB address will be displayed.

2. Select GPIB address

By turning the knob, GPIB address can be selected.

When desired GPIB address is displayed, press Remote / Local key. By pressing Remote / Local key, the settings will be saved in the non-volatile

memory and Saved message will be displayed.

If you didn’t change any of the previous set parameters, the power supply will display No Change message. If you did change a single parameter from the previous set parameters, Saved

message will be displayed. After one of these messages is displayed for several seconds, the power supply returns to the previous state.

GPIB / 488

ADDR 05

Remote Mode and Indicators

When RS-232 interface is selected, SYSTem:REMote command must be the first sent command. Otherwise, if another command is sent first, Power supply

in local mode message will be sent to PC.

While in remote interface mode of operation (after sending SYSTem:REMote command), rmt indicator will be displayed. In this case, all front panel keys are disabled, except Remote / Local key, which is active. This key allows you to

put the power supply in local mode of operation, so all front panel keys become active.

In order to control the power supply using remote commands again,

SYSTem:REMote command must be sent again, before any other commmand.

When GPIB interface is selected, adr indicator is displayed when the power

supply is addressed (either as a Listener or as a Talker) or when a GPIB command is sent over the interface.

When SYSTem:REMote command is sent over the GPIB interface, an error will be generated: Err 501, Command allowed only in RS -232.

Errors / Calibrate Key

This key has a double function: errors related in normal mode (see this section) and calibration related in calibration mode (see calibration section).

There are 2 types of errors: user defined errors and errors defined by SCPI 1999 standard.

Every time an error is generated, a beep will be generated by the power supply and err indicator will be displayed.

Generated errors are saved in an error queue, in FIFO (first in – first out) order. If more than 20 errors are generated, the last error is overwritten with –350

error (queue overflow error) and no more errors are saved.

While in remote mode (rmt indicator is displayed), errors are erased from the queue as you read them.

By pressing Errors / Calibrate key, you enter Errors / Calibrate menu. By turning the knob, following options are displayed:

Options are selected by pressing Errors / Calibrate key when the desired option is displayed.

Errors option allows you to view the generated errors. If you press Errors / Calibrate key again, by turning the knob you can see

all generated errors. Error’s code will be displayed. When all errors were viewed, if continue to turn the knob, they will be displayed again.

After you viewed all errors, you press Errors / Calibrate key again. The power supply will erase all the errors from the error queue and Errors

Erased message will be displayed.

Errors

Exit

Cal String

Errors

After several seconds the power supply will go back to normal mode. The err indicator will not be displayed anymore.

If there are no errors in the queue and you select Errors option in order to view the errors, the power supply will display:

And then it will return to normal mode.

There are 3 ways of erasing the error queue:

♦ By turning off and then turning on the power supply ♦ By pressing Errors / Calibrate key after errors are displayed, in local

mode

♦ By reading errors, in remote operation.

Important note! If you let the display time out while viewing errors locally, the power

supply will go back to normal mode, without erasing the error queue.

The power supply allows you to store a calibration message. It may contain last calibration date, the date when the next calibration must be done or the

name and the phone number of the person to contact for a new calibration.

This message can have up to 40 characters. It can be set only remote interface and it is saved in non-volatile memory.

When delivered, the power supply has the following calibration string set: “CALIBRATION DATE: MMM/DD/YYYY” (for example:

CALIBRATION DATE: Feb/11/2005)

Cal String option allows you to view the calibration string.

If you press Errors / Calibrate key when Cal String option is displayed, the calibration message will be displayed. To increase the scrolling speed,

you must press > key. To decrease scrolling speed, you must press < key.

No Errors

Cal String

After the first scrolling of the calibration message, < or > keys must be pressed in order to scroll the message again.

Exit option allows you to leave this menu, without changing anything. Exiting message will be displayed and the power supply returns to the

previous state (the state before entering this menu).

Important note! If you enter in the Errors / Calibrate menu and no action takes place for approx. 20 seconds, the power supply leaves this menu. Exiting message is

displayed and the power supply returns to the previous state (the state before entering Errors / Calibrate menu).

Exit

Calibration Overview

Calibration is a procedure that ensures that the power supply will work properly, with parameters specified within Technical Specification section.

Before initiating the calibration procedure, the following conditions must be assured:

disconnect any loads connected to the power supply and turn it on

let the power supply turned on for 1 hour, with no loads connected before

you start the calibration procedure

calibration ambient temperature must be 25 0C

ambient relative humidity must be less then 80%.

Recommended calibration interval is 1 year.

Important note!

In ord er to perform the calibration procedure, a digital multimeter is needed. It must have the following characteristics:

Voltage resolution: 0.1 mV Current resolution: 0.01 mA Acurracy: 0.01 %

Calibration Security Code

To prevent accidental or unauthorized calibration procedures, the power supply has a calibration security code. This security code is optional, so you may have

it or not. The power supply will work properly in both cases.

Security code may contain numbers (0..9), small letters (a..z) and spaces (“ “). Any of these characters may be used as the first character in security code.

Security code may contain up to 11 characters. But it is not necessary for you to use all 11 characters for the security code.

The security code is saved in non-volatile memory and it doesn’t change when you turn on or turn off the power supply.

When delivered, power supply has the following security code: 0000

In order to initiate the calibration procedure, first you must unsecure the power supply (if a security code is set).

Unsecure Procedure for Calibration

To unsecure the power supply, the next steps bust be followed:

1. Turn on the power supply in calibrating mode

To enter calibrating mode, you must turn on the power supply while pressing Errors / Calibrate key. You release the key after the long beep. After that, the

power supply will display:

if the power supply is secured (if the power supply has a security code set). If this message is displayed, go to step 2.

or :

if the power supply is not secured (if the power supply has been turned off after the unsecure procedure). If the power supply is already unsecured, you can proceed with calibration (see

Calibration procedure section)

2. Enter security code

Press OVP / Secure key. The power supply will display:

Here you must enter the security code, using > < keys and knob. The selected digit has the cursor underneath it. If you set the digit to the desired value, you must press > key and go to the next digit, if you want.

After you entered th e security code, press OVP / Secure key and if the security code is correct, the power supply will display:

Calibrating Mode Secured

Calibrating Mode Unsecured

Security code: _ _ _ _ _ _ _ _ _ _ _

Calibrating Mode Unsecured

From this moment you can proceed with calibration (see Calibration procedure section) or you can go back to normal mode operation. From now on, the power supply remains unsecured until you set a new secure

code.

If the security code you entered is not correct, power supply will display:

for 1 second. 703 error (Invalid secure code) and a short beep will be generated. You can see the error in normal mode operation (by pressing Local

key). After that power supply will display again:

and you must enter security code again , using < > keys and knob. If you don’t remember the correct security code, you may follow the hardware unsecure procedure (see Hardware unsecure procedure ).

Important Note! While in calibrating mode, before you unsecure the power supply, only Local,

< > and Secure keys are active (all the rest are locked). The knob is also active. Local key can be used at any moment of unsecure procedure to leave

calibrating mode and go back to normal mode operation. Secure key is used in unsecure procedure of the power supply (allows you to enter and validate the secure code).

While in calibrating mode, after you unsecure the power sup ply, only Local,

Secure, < > and Calibrate keys are active. The knob is also active. Local key is used to leave calibrating mode and go back to normal mode

operation. Secure key is used to set a new security code (you may introduce a new

security code and secure again the power supply).

Calibrate key is used to proceed with calibration.

Attention! Local key is active all the time while in calibrating mode and by pressing it the

power supply returns to normal mode. Leaving the unsecure procedure (before

Security code: invalid

Security code: _ _ _ _ _ _ _ _ _ _ _

it is finished) does not change anything concerning the secure state of the power supply (secured or unsecured).

After you changed the security code or unsecured the power supply, you can go back to normal mode by pressing Local key. (You can come back to

calibrating mode only by turning off the power supply and starting it in calibrating mode).

But once you started the calibration procedure, it is recommended to finish it and to go back to normal mode by turning off and on the power supply.

Hardware Unsecure Procedure for Calibration

This procedure may be used to unsecure the power supply if you forgot the security code.

To unsecure the power supply without using the security code, follow the next steps:

1. Turn off the power supply. Disconnect the power cord and all loads

connected to the power supply.

2. Remove power supply’s cover. Set J6 jumper for hardware unsecuring

mode.

3. Connect the power cord to the power supply. Turn on the power supply in

calibrating mode.

4. Unsecure the power supply.

To unsecure the power supply you must press Secure key. Power supply will display:

Press again Secure key the power supply will display:

Here any security code may be introduced, since it is not verified by the power supply.

Press again Secure key and you will unsecure the power supply. It will display:

J5 J6

Normal

unsecuring

J5 J6

Hardware

unsecuring

Calibrating Mode Secured

Security code: _ _ _ _ _ _ _ _ _ _

Calibrating Mode Unsecured

The power supply remains unsecured until you enter a new security code.

Important note!

Even if you are in calibrating mode, you cannot set a security code as long as the J6 jumper is in hardware unsecuring position.

5. Set J6 jumper for normal unsecuring mode.

Important note!

If you turn on the power supply in either normal mode or calibrating mode and

J6 jumper is in hardware unsecuring position, error 701 (Calibration security disabled by jumper) will be generated.

6. Turn off the power supply and reassemble it.

Calibration Procedure

Before initiating the calibration procedure, the following conditions must be assured:

disconnect any loads connected to the power supply and turn it on

let the power supply turned on for 1 hour, with no loads connected before

you start the calibration procedure

calibration ambient temperature must be 25 0C

ambient relative humidity must be less then 80%.

On calibration procedure there are three parameters that must be calibrated: voltage, OVP and current.

You can leave the calibration procedure at any time by turning off the power supply or by pressing Local key.

But once you started the calibration procedure, it is recommended to finish it and to go back to normal mode by turning off and then turning on the power supply.

In order to be sure that the power supply will work properly in normal mode after you leave the calibration procedure, you must turn off the power supply.

Recommended calibration interval is 1 year.

Before calibrating the power supply you must unsecure it, if secured (see Calibration Overview section).

After you unsecured the power supply and you pressed Calibrate key, you go to Calibrate menu. By turning the knob next options are available:

1. Volt Zero Scale

2. Volt Full Gain

3. OVP

4. Curr Zero Scale

5. Curr Full Gain

Options are selected by pressing Calibrate key.

Important note!

In order to perform a correct calibration, the calibration procedures from the Calibrate menu must be followed in the order they are displayed by the power

supply.

Voltage Calibration Procedure

After you unsecured the power supply and you pressed Calibrate key, you entered calibrate mode.

Volt Zero Scale Calibration

1. Select Volt Zero Scale calibration procedure

In order to start voltage calibration procedure, you must select Volt Zero Scale option.

The power supply will display:

You select this option by pressing Calibrate key. The power supply will display:

2. Initiate DAC calibration procedure

Connect a digital voltmeter to the output terminals of the power supply. After that, you must adjust DAC value displayed by the power supply until the voltmeter indicates the closest possible to 0.000 V value.

For this, you use > < keys and the knob.

It is not necessary to disconnect the digital voltmeter, since you will need it later on calibration procedure!

3. Initiate ADC calibration procedure

Press Calibrate key. This will initiate ADC calibration procedure. The power supply will display:

After ADC calibration, power supply will return to Calibrate menu Volt Full Gain calibration procedure.

Calibrating Mode Volt Zero Scale

Volt Zero Scale DAC:1999

Volt Zero Scale ADC Calibrating

Volt Full Gain Calibration

1. Select Volt Full Gain calibration procedure

In order to finish voltage calibratio n procedure, you must select Volt Full Gain option.

The power supply will display:

You select this option by pressing Calibrate key. The power supply will display:

2. Initiate DAC calibration procedure Connect a digital voltmeter to the output terminals of the power supply. After that, you must adjust DAC value displayed by the power supply until the

voltmeter indicates the correct voltage value, depending on the model of the power supply (see the table bellow).

Power supply model Voltage value for

Volt Full Gain calibration

9120 16.3840 V 9121 16.3840 V 9122 32.7700 V 9123 16.3840 V

For this, you use > < keys and the knob

3. Initiate ADC calibration procedure Press Calibrate key. This will initiate ADC calibration procedure. The power supply will display:

After ADC calibration, power supply will return to Calibrate menu, OVP calibration procedure.

Calibrating Mode Volt Full Gain

Volt Full Gain DAC:31470

Volt Full Gain ADC Calibrating

OVP Calibration

While performing this calibration procedure, the power supply must have no loads connected to the output terminals.

1. Select OVP calibration procedure

In order to initiate OVP calibration procedure, you must select OVP option. The power supply will display:

You select this option by pressing Calibrate key. The power supply will display:

Important note! This calibration procedure will take several minutes.

After OVP calibration, power supply will return to Calibrate menu, Current calibration procedure.

Calibrating Mode OVP

Calibrating OVP Please wait…

Current Calibration Procedure

Current calibration procedure must be permormed after Voltage calibration

procedure.

Current Zero Scale Calibration

While performing this calibration procedure, the power supply must have no loads connected to the output terminals.

1. Select Curr Zero Scale calibration procedure

In order to start current calibration procedure, you must select Curr Zero Scale option. The power supply will display:

2. Initiate DAC calibration procedure

You select this option by pressing Calibrate key. So Current Zero Scale calibration procedure will be initiated.

The power supply will display:

After a while, the power supply will display:

Important note! This calibration procedure will take several minutes.

After Current Zero Scale calibration procedure, power supply will return to Calibrate menu, Curr Full Gain calibration procedure.

Calibrating Mode Curr Zero Scale

Curr Zero Scale ADC:Calibrating

Curr Zero Scale DAC:Calibrating

Current Full Gain Calibration

1. Select Curr Full Gain calibration procedure In order to finish current calibration procedure, you must select Curr Full

Gain option.

The power supply will display:

You select this option by pressing Calibrate key. The power supply will display:

2. Initiate DAC calibration procedure In order to initiate Curr Full Gain calibration procedure, you must connect a

digital ammeter to the output terminals of the power supply. If don’t connect a digital ammeter within 30 seconds, the power supply will

display:

and it will return to Calibrate menu.

After you connected the digital ammeter, you must adjust DAC value displayed by the power supply until the ammeter indicates indicates the correct current

value, depending on the model of the power supply (see the table bellow).

Power supply model Current value for

Curr Full Gain calibration

9120 2.62144 A 9121 2.62144 A

9122 1.31072 A 9123 2.62144 A

For this, you use > < keys and the knob

Calibrating Mode Curr Full Gain

Curr Full Gain Connect Ammeter

Calibrating Mode CC Not Set

3. Initiate ADC calibration procedure

Press Calibrate key. This will initiate ADC calibration procedure. The power supply will display:

After ADC calibration, power supply will return to Calibrate menu.

In this moment, the calibra tion procedure is finished. By presing Local key, the power supply will return to local mode.

Important note! In order to be sure that the power supply will work properly in normal mode

after you leave the calibration procedure, you must turn off the power supply.

Curr Full Gain ADC Calibrating

OVP / Secure Key

This key has a double function: OVP settings in normal mode operation and secure key in calibration mode operation (for the latter see Calibration

section).

In this section OVP functions will be described.

OVP circuit prevents the output voltage from rising above a programmed voltage value. So the load connected to the output terminals is protected of

overvoltage situations.

Overvoltage protection circuit is activated when output voltage value becomes equal or greater than the programmed trip level for overvoltage protection circuit.

OVP Menu Overview

By pressing OVP / Secure key, you enter OVP menu. Here, programmed OVP trip level will be displayed.

When you turn on the power supply, OVP trip level is OVP trip level value saved at power_up state (state 0). This value can be changed by the user (and

saved in power_up state if wanted).

Here you can set desired OVP trip level, by using > < keys to select the digit you want to adjust (selected digit has the cursor underneath) and knob to set the

digit to desired value.

The programming range for OVP trip level depends on the model of the power supply (see the table bellow):

Power supply

model

OVP min value OVP max value

9120 1 V 33 V 9121 1 V 22 V 9122 1 V 63 V 9123 1 V 33 V

The OVP trip level you set is saved by pressing OVP / Secure key.

After that, you enter the OVP menu.

By turning the knob, following options are displayed:

Options are selected by pressing OVP / Secure key when the desired option is displayed.

OVP On option enables overvoltage protection circuit. OVP trip level is the level value you programmed on Level option (after you first pressed OVP /

Secure key).

If you want to keep the previously programmed trip level, you simply press OVP / Secure key, without changing anything.

If you enable the overvoltage protection circuit, when you return to normal mode, ovp indicator will be displayed.

OVP Off option makes OVP trip level equal to maximum availabale OVP value, no matter what what value is set in OVP menu (but the value from

OVP menu does not change). For maximum available OVP value, see the table above.

If you select OVP Off option, when you return to normal mode, ovp indicator will not be displayed anymore.

Important note!

When OVP On option is selected, OVP trip level is equal to the programmed level, shown in OVP menu.

When OVP Off option is selected, OVP trip level is equal to the maximum available value for this parameter, depending on the model of the power

OVP On

OVP Off

OVP Clear

OVP On

OVP Off

supply (see the table above). In this case, the programmed OVP trip level, shown in OVP menu does not change!

OVP Clear option is used to clear to OVP condition (for more information about how you get back to normal mode after OVP level was tripped, please

refer to the next section).

After you select the desired option, a message will be displayed. If you didn’t change anything of the previous set parameters, the power supply will display No Change message.

If you did change a single parameter from the previous set parameters Done message will be displayed. After one of these messages is displayed for several seconds, power supply

returns to normal mode.

Important note! If you enter in the OVP menu and no action takes place for approx. 20 seconds, the power supply will leave the OVP menu. No Change message is displayed

and the power supply returns to the previous state (the state before entering OVP menu).

If the output voltage value becomes equal or greater than OVP programmed level and the overvoltage protection circuit is enabled, the power supply will

display:

And the output voltage value will be 0 V (output is disabled).

There are three ways of clearing the OVP condition:

Ø By increasing OVP trip level and clearing the OVP condition Ø By decreasing the output voltage and clearing the OVP condition

Ø By disabling OVP circuit and clearing the OVP condition

Important note!

When you turn on the power supply, the overvoltage protection circuit is enabled and the OVP trip level is equal to the one saved in power_up state

(factory setting: maximum available value).

Over Voltage Output Off

OVP Clear

Programming OVP Circuit in Front Panel Mode

If you want to program an OVP trip level and to enable the overvoltage protection circuit using front panel keys, follow the next steps:

1. Turn on the power supply

When you turn on the power supply, the overvoltage protection circuit is enabled and OVP trip level is set to maximum available value for OVP parameter, depending on the model of the power supply (see table in the

prevous section).

2. Enter the OVP menu and set OVP trip level

By pressing OVP / Secure key, you enter the OVP menu. The power supply will display the programmed OVP trip level.

For changing this value, you can use > < to select the digit you want to adjust (selected digit has the cursor underneath) and then turn the knob to set the desired value.

After you set the desired value for OVP trip level, you press OVP / Secure key.

Important note!

You cannot set an OVP trip level lower than 1 Volt. The maximum OVP trip level value depends on the model of the power supply

(see table in the previous section )

3. Enable the OVP circuit After you set the desired OVP trip level and you pressed OVP / Secure key,

OVP On, OVP Off and OVP Clear options are available. To enable the OVP circuit, you select OVP On option by turning the knob

4. Exit the OVP submenu

To exit the OVP submenu and to validate all the settings you have done, then you press OVP / Secure key.

After that, Changed message will be displayed and the power supply return to previous state (the state before you entered the OVP submenu), in normal mode

operation.

ovp indicator will be displayed. If you didn’t change anything, the power supply will display No Change message.

OVP On

Clearing Overvoltage Condition

There are three ways of clearing the OVP condition:

Ø By increasing OVP trip level and clearing the OVP condition Ø By decreasing the output voltage and clearing the OVP condition Ø By disabling OVP circuit and clearing the OVP condition

Attention!

The latter solution disables the OVP circuit, but the first and the second don’t!

In this section we will describe the steps you must follow to clear the OVP condition in all three cases.

If the output voltage value becomes equal or greater than OVP programmed level and the overvoltage protection circuit is enabled, the power supply will

display:

And the output voltage value will be 0 V (output is disabled).

Over Voltage

Output Off

Clear OVP Condition by Increasing OVP Trip Level

1. Enter the OVP menu By pressing OVP / Secure key, you enter the OVP menu.

2. Adjust OVP trip level

When you enter OVP menu, OVP trip level is displayed. Here, you set OVP trip level to a level higher than the programmed voltage value (U

lim

3. Clear OVP condition

After you set the OVP trip level, you press OVP / Secure key. Here, OVP On, OVP Off, OVP Clear options are available. Select OVP

Clear option by turning the knob.

After that, press OVP / Secure key. The power supply will display:

and after several seconds it will return to normal mode. ovp indicator will be displayed (the OVP circuit is still enabled).

Important note! If you enter the OVP menu and no action takes place for approx. 20 seconds,

the power supply will leave the OVP menu. No Change message is displayed and the power supply returns to the previous state (the state before entering

OVP menu).

OVP Clear

Clear OVP:Done

Clear OVP Condition by Decreasing the Output Voltage

1. Decrease the output voltage level bellow OVP trip level

Press Limit key and enter limit mode. Limit values of voltage and current will be displayed. ovp and lmt indicators will also be displayed.

Adjust for output voltage limit to a lower value than the OVP trip level.

Press Limit key to exit limit mode.

2. Enter OVP menu and clear OVP condition

Here you check that the OVP trip level is greater than the output voltage limit you set. If it isn’t, go to step 1.

Don’t adjust OVP trip level!

Clear OVP condition by turning the knob and selecting OVP Clear option:

After that, press OVP / Secure key. The power supply will display:

and after several seconds it will return to normal mode. ovp indicator will be displayed (the OVP circuit is still enabled).

Important note! If you enter OVP menu and no action takes place for approx. 20 seconds, the power supply will leave the OVP menu. No Change message is displayed and

the power supply returns to the previous state (the state before entering OVP menu).

OVP Clear

Clear OVP:Done

Clear OVP Condition by Disabling OVP Circuit

1. Disable OVP circuit

By pressing OVP / Secure key, you enter OVP menu. Here you disable OVP circuit by turning the knob and selecting OVP Off option.

It doesn’t matter if you change or not OVP trip level as long as you disable the OVP circuit. But you must be careful to set it to the right value before you

enable OVP circuit next time.

After you selected OVP Off option and you pressed OVP / Secure key, the power supply will display

because you didn’t clear the OVP condition yet

2. Enter OVP menu and clear OVP condition

You enter OVP menu again by pressing OVP / Secure key. Now you clear OVP condition by turning the knob and selecting OVP Clear option:

After that, press OVP / Secure key. The power supply will display:

and after several seconds it will return to normal mode. ovp indicator will be displayed (the OVP circuit is still enabled).

Important note! If you enter in the OVP menu and no action takes place for approx. 23 seconds, the power supply will leave the OVP menu. No Change message is displayed

and the power supply returns to the previous state (the state before entering OVP menu).

OVP Off

Over Voltage

Output Off

OVP Clear

Clear OVP:Done

Rear Panel Description

On the rear panel of the power supply there are:

RS-232 interface connector

AC inlet

Power-line fuse-holder assembly

Rear output terminals.

-s

The sensing terminals (+s and -s) are connected to the outp ut terminals of the power supply by jumpers. For the power supply to work properly, the jumpers must be kept in that

position.

Remote Interface

For remote communication, there are two available interfaces: GPIB / 488 interface and RS-232 interface. The selected interface and the coresponding

settings are saved in a non-volatile memory and does not change after the power supply is turned off or after a *RST command.

Only one interface can be active at a time. When the power supply is delivered, GPIB / 488 interface is selected.

RS-232 Interface

In order to connect the power supply to the RS-232 interface, the male DB-9 connector from the rear panel must be used. For all communication sessions

over RS-232 interface, the power supply usses two handshake lines: DTR (Data Terminal Ready, pin 4) and DSR (Data Set Ready, pin 6).

For more information about the DB-9 connectorand about the connection to a computer terminal, please refer to Interface Cable section.

A character frame transmitted over RS-232 interface consists of one start bit, seven data bits and a parity bit / eight data bits and no parity and a stop bit.

Here is the frame format used by the power supply:

Parity even/odd:

No parity:

After start bit, least significant bit is sent first.

Start

bit

8 Data

bits

Parity

bit

Stop

bit

Start

bit

7 Data

bits

Stop

bit

GPIB / 488 Interface

GPIB / 488 interface availability for different models:

9120 9121 9122 9123 RS-232 Standard Standard Standard Standard

GPIB / 488 Optional Optional Optional Standard

GPIB (General Purpose Interface Bus) interface is also known as IEEE 488.

The original 488.1 specification defines the mechanical and electrical characteristics of the interface and its fundamental protocols.

The 488.2 specification defines a minimum configuration, and adds specifications for a basic set of instrument commands and common data

formats.

In order to communicate with the power supply over GPIB interface, a GPIB interface card must be placed in the computer.

A GPIB system allows interconnection of instruments and other devices to a controlling computer.

Here are some specifications of IEEE 488.1:

Up to 15 devices may be interconnected in a GPIB network

Configuration of the bus network may be linear or bus

24 bus lines: 8 data lines, 8 control and management lines, 8 GND

lines

Data transfer mode: 8-bit parallel

Handshake: '3 wire handshake'; reception of each data byte is

acknowledged.

total transmission path length: 20m, or L < 2N

L – total transmission path length N – number of devices

Maximum transmission rate: 1 megabyte per second. The actual

data rate is determined by the slowest device.

Each device connected to the interface must have a unique address

between 0 to 30 (decimal value).

Functional Description of GPIB Interface

Devices from the interface are classified into 3 types:

Listener: a device capable of receiving data over the interface when addressed to listen by the Active Controller. There can be up to 14 Listeners on the bus at one time.

Usually the Active Controller will be the Talker, while a single device is the Listener.

But it is also possible that multiple Listeners will be assigned. In this case, all of them will execute the received commands.

A device becomes a Listener when it is addressed to listen (when it receives its Listen address). It stops being a Listener only when:

UNL command is received

Interface Clear (IFC) command is sent over the interface.

Talker: a device capable of transmitting data over the interface when addressed to talk by the Active Controller. There can be only one Talker on the bus at one time.

Usually, when a device is addressed to talk, it becomes the Talker over the interface and Active Controller becomes a Listener.

A device becomes a Talker when it is addressed to talk (when it receives its Talk address).

It stops being a Talker only when:

UNT command is received

A new Talker is assigned (since there can be only one addressed

Talker on the bus at one time )

Interface Clear (IFC) command is sent over the interface

Controller: a device capable of specifying the Talker and the Listeners for a data or command transfer. In multiple controller systems, active control may be passed between

controllers. There can be only one addressed Controller on the bus at one time. The Controller function is usually handled by a computer.

The power supply can only be a Listener or a Talker (when addressed to talk).

IEEE 488 Addressing

An IEEE 488 address can take values from 0 to 30.

When supplied from the factory, pow er supply’s GPIB address is 5.

An IEEE 488 device has a Listen address and a Talk address. Listen address and Talk address bytes are different.

Listen address is defined by adding decimal value of 32 to the address. Talk address is defined by adding decimal value of 64 to the address.

Decimal value of 31 is a special address value. Listen address byte has the value of 63 decimal (31 + 32 = 63 decimal). This is a special address byte,

called Unlisten (UNL). This address byte is sent by the Controller before assigning new Listeners. It tells to the currently assigned Listeners to stop listening.

For decimal value of 31, Talker address byte has the value of 95 (31 + 64 =

95). This is a special address byte, called Untalk (UNT). This address byte is sent by the Controller and it tells to the currently addressed Talker to stop being

a Talker, because a new Talker will be assingned.

This power supply has no secondary address implemented.

Bus Description

The interface signal lines are organized into three functional groups:

- Data lines (8 lines)

- Handshake lines (3 lines)

- General bus management lines (5 lines)

The bus signal lines use low true logic protocol.

Data lines:

- allow transfer of one byte at a time.

- Bytes are transferred over the interface in a byte-serial, bit-parallel

manner.

- DIO1 represents least significant bit of the byte, while DIO8 represent

most significant bit of the byte transffered over the interface.

Handshake lines:

- control byte transfer between devices, using 3-wire handshaking.

- the speed of the data transfer is given by the slowest listener, so every

listener can read bytes transferred over the interface correctly.

- reception of each data byte is acknowledged.

DAV (Data Valid)

- this line is controlled by the Talker

- the talker sets DAV line true (active low) when all devices from bus

release NRFD line (NRFD line high).

- DAV line true means that data byte is stable on the bus (so it can be

read by the listeners).

NRFD (Not Ready For Data)

- this line is controlled by the Listeners to indicate to the Talker if they

are ready to receive new data.

- NRFD line will not go high until all Listeners release the line.

NDAC (Not Data Accepted)

- this line is controlled by the Listeners to indicate to the Talker if data

was read from the bus

- when NDAC line false (high), addressed Listeners indicate that they

read the data from the bus

- NDAC line will not go high until all Listeners release the line.

General bus management lines:

- ATN, IFC, REN, SRQ, EOI and they are used by the Active

Controller or System Controller to manage GPIB interface

SRQ (Service Request):

- This line is used by any device from the bus.

- when is set true (low), the device notifies the Controller that it needs

servicing a request.

- Controller will perform a Serial Poll or a Parallel Poll in order to

determine which device requested a service and why.

IFC (Interface Clear):

- This line is used only by the Controller.

- When IFC line is true (low) all devices from the bus reset the GPIB

interface (Talker and Listeners are unaddressed, service request idle and Serial Poll disabled).

REN (Remote Enable):

- This line is used only by the Controller.

- When REN line is set true (low), the bus is in remote mode, so devices

can be addressed to listen or to talk.

- A device will go into remote mode only when addressed to listen.

While in remote mode, the device ignores its local front panel controls (only Remote / Local key is active) and it receives instructions over

GPIB interface.

- when REN line is set false (high), the bus and all devices go to local

mode.

EOI (End or Identify):

- this line is used by the active Talker

- when EOI line is true (low), the active Talker indicates that the last

byte of a data stream is sent over the interface.

- multiple termination schemes are available, depending on the GPIB

interface card you use.

ATN (Attention):

- this line is used only by the Controller

- when ATN line is true (low), the bus is in command mode. Address

and GPIB command bytes are transferred over the interface. These bytes are used to assign Lis teners and Talker, to obtain device status etc. All devices from the bus must acknowledge them.

- when ATN line is false (high), the bus is in data mode and data bytes

are transferred over the interface. These bytes may be SCPI commands sent by the addressed Talker to the addressed Listeners.

or a response sent by a previously interrogated Listener (eg: response to an interogative command). The interrogated device must be addressed as a Talker in order to be able to transmit the response.

Only addressed Listener (s) will acknowledge them.

SendingCcommands over GPIB Remote Interface

GPIB byte commands are sent together with address bytes while ATN line is low.

SCPI commands are sent after address bytes are sent. The power supply must be addressed as Listener. While sending address bytes, ATN line is low. While sending SCPI commands, ATN line is high.

If the SCPI command is interrogative, after sending the command, the Active Controller must address the power supply as a Talker. Then ATN line goes

high and the power supply can send the answer to the Active Controller.

Command terminators

When GPIB interface is selected, a command string sent to the power supply may terminate in different ways, depending on the GPIB interface card.

Line feed character (0a h) combined with EOI line low

Line feed character (0a h) and carriage return character (0d h)

combined with EOI line low

EOI line low

For multiple commands sent in a single message, command

separator is semicolon character (03b h). When multiple commands are sent in the same message, EOI line

goes low while the last character of the message is sent (it may be line feed character, carriage return character or the last character of the last command).

When addressed as a Talker, the power supply use the following termination scheme: line feed character combined with EOI line low.

When Status Byte is transmitted by the power supply (part of Serial Poll Procedure), EOI line does not go low.

Serial Poll Procedure

When serial poll procedure is initiated, a device is addressed to talk and Active Controller sends Serial Poll Enable command (ATN line is low, because addresses and GPIB command bytes are transferred over the interface).

The addressed device sends back to Active Controller a Status Byte (ATN line is high, because data bytes are transferred over the interface).

Then, the Active Controller sends Serial Poll Disable command (ATN line is low, because address and command bytes are transferred over the interface) to

end the serial poll sequence.

In order to obtain Status Byte from each device from bus, Active Controller addresses the devices one by one.

Status By te of each device must be analyzed. This makes serial poll procedure to be relatively slow for large systems.

Interrogative Commands Over GPIB Interface

After receiving an interrogative command, when the response is ready to be read, Message Available Bit (bit 4 of Status Byte Register) is set. Serial Poll

Enable command can be sent to read Status Byte. Any other ommand (except Serial Poll) clears the output buffer and the

response to the previous interrogative command is lost. In this case an error is generated by the power supply (Err -410, Query interrupted) and MAV bit is cleared.

In order to read the response to the previous in terrogative command, the power supply must be addressed as a Talker.

After the response is sent MAV bit is cleared.

MAV bit is also set when the power supply receives a command and it is not able to execute it. Err -365, Timeout error message will be available in the

output buffer of the power supply.

When MAV bit is set, the power supply has a message to transmit to the Active Controller. The power supply has to be addressed as a Talker in order to be able to transmit the message.

Commands Sent Over Remote Interface

There are several types of commands that can be sent over the remote interface, in order to control the power supply:

SCPI (Standard Commands for Programmable Instruments) commands

- these commands are defined in the Power Supply Instrument Classes

of the 1999 SCPI standard.

- a complete description of synthax and functionality is contained in the

1999 SCPI standard.

- these commands can be sent over RS-232 interface and GPIB / 488

interface.

Non-SCPI commands

- these commands are power supply specific.

- these commands can be sent over RS-232 interface and GPIB / 488

interface.

IEEE 488.2 commands

- The 488.2 specification defines a minimum configuration, and adds

specifications for a basic set of instrument commands.

- these commands can be sent over RS-232 interface and GPIB / 488

interface.

IEEE 488 bus commands

- in command mode, the power supply can receive talk and listen

addresses, universal commands and addressed commands (for more information, please refer to IEEE 488 bus commands section).

- These commands can be sent over GPIB interface

Introduction to SCPI Language

Here are some conventions used in SCPI standard: ♦ A command consists of a command keyword (command name) and a

parameter (it may be optional or not)

♦ Lower case and upper case letters are considered equivalent ♦ Letter case is used to differentiate between the accepted short form (the

uppercase characters) and the long form (the whole keyword)

♦ Square brackets ( [ ] ) are used to enclose:

♦ a keyword that is optional when programming the command ♦ one or more parameters that are optional when controlling the

instruments. If no parameter is specified, default parameter is considered. The braces are not sent with the command string.

♦ Braces or curly brackets ( {} ) are used to enclose one or more parameters

that may be included zero or more times. The braces are not sent with the command string.

♦ The angle brackets (<>) are used to enclose the type name.

A value of the specified type must be added to the command. The angle brackets are not sent with the command string.

♦ The vertical bar ( | ) can be read as “or” and it is used to separate

alternative parameter options. Only one parameter can be sent with the command.

♦ The query form of a command is generated by appending a q uestion mark

to the last keyword. Not all commands have a query form and some commands exist only in query form.

SCPI Command Terminators

A command string sent to the power supply must terminate with a new line character (ASCII decimal code of 10) or a a carriage return character (ASCII

decimal code of 13).

For multiple commands sent in a single message, command separator is semicolon character (03b h).

Important note! The power supply will go to remote mode of operation (it can accept

commands over RS-232 interface) if SYSTem:REMote command is sent.

If other remote interface commands are sent before sending SYSTem:REMote command, the power supply will respond with Power supply in local mode

message.

SCPI Commands

DISPLAY Subsystem

:DISPlay [:WINDow][:STATe ] {OFF|ON}

[:WINDow][:STATe ]? [:WINDow]:TEXT[:DATA] <quoted string> [:WINDow]:TEXT[:DATA]? [:WINDow]:TEXT:CLEar

MEASure Subsystem

:MEASure :CURRent[:DC]?

[:VOLTage][:DC]?

MEMory Subsystem

MEMory:STATe :NAME <numeric value>,<quoted string>

:NAME? <numeric value>

OUTPut Subsystem

:OUTPut [:STATe] {OFF|ON} [:STATe]?

SOURce Subsystem

[:SOURce] :CURRent[:LEVel][:IMMediate][:AMPLitude] {<current>|MIN|MAX|UP|DOWN} :CURRent[:LEVel][:IMMediate][:AMPLitude]? [MIN|MAX]

:CURRent[:LEVel][:IMMediate]:STEP[:INCrement] {<numeric value>|DEFault} :CURRent[:LEVel][:IMMediate]:STEP[:INCrement]? [DEFault] :CURRent[:LEVel]:TRIGgered[:AMPLitude] {<current>|MIN|MAX} :CURRent[:LEVel]:TRIGgered[:AMPLitude]? [MIN|MAX]

:VOLTage[:LEVel][:IMMediate][:AMPLitude] {<voltage>|MIN|MAX|UP|DOWN} :VOLTage[:LEVel][:IMMediate][:AMPLitude]? [MIN|MAX] :VOLTage[:LEVel][:IMMediate]:STEP[:INCrement] {<numeric value>|DEFault} :VOLTage[:LEVel][:IMMediate]:STEP[:INCrement]? [DEFault] :VOLTage[:LEVel]:TRIGgered[:AMPLitude] {<voltage>|MIN|MAX}

:VOLTage[:LEVel]:TRIGgered[:AMPLitude]? [MIN|MAX]

:VOLTage:PROTection[:LEVel] {<voltage>|MIN|MAX} :VOLTage:PROTection[:LEVel]? [MIN|MAX] :VOLTage:PROTection:STATe {0|1|OFF|ON}

:VOLTage:PROTection:STATe? :VOLTage:PROTection:TRIPped? :VOLTage:PROTection:CLEar

STATus Subsystem

STATus:QUEStionable [:EVENt]?

:ENABle <enable value> :ENABle?

SYSTem Subsystem

:SYSTem :BEEPer[:IMMediate] :COMMunicate:GPIB:RDEVice:ADDRess <numeric value> :COMMunicate:GPIB:RDEVice:ADDRess? :ERRor?

:INTerface GPIB|RS232

:VERSion?

TRIGger Subsystem

INITiate[:IMMediate] TRIGger[:SEQuence]:DELay {<seconds>|MIN|MAX}

TRIGger[:SEQuence]:DELay? [MIN|MAX] TRIGger[:SEQuence]:SOURce {BUS|IMM} TRIGger[:SEQuence]:SOURce? *TRG

Non-SCPI commands

SET {<voltage>|DEF|MIN|MAX}[,<current>|DEF|MIN|MAX] SET?

CALibration:MESSAGE <quoted string> CALibration:MESSAGE?

SYSTem:REMote

IEEE 488.2 commands

*CLS *ESE <enable value>

*ESE? *ESR?

*IDN? *OPC *OPC?

*PSC {0|1} *PSC? *RCL {0 | 1 | 2 | … | 99}

*RST *SAV {0 | 1 | 2 | … | 99} *SRE <enable value>

*SRE? *STB? *TRG

IEEE 488 bus commands

DCL LLO

SPE SPD GET

SDC GTL

SCPI commands overview

DISPlay Subsystem

This subsystem controls the presentation of textual information and measurement data.

:DISPlay[:WINDow][:STATe] {0|1|OFF|ON}

This command turns power supply’s display off and on. When the display is off, only indicators are displayed. When the display is on, power supply is in nomal mode (measured or

programmed values of voltage and current are displayed.). You can replace off|on parameters with 0|1 numeric values.

:DISPlay[:WINDow][:STATe]?

This command queries front panel display status. It returns only numeric values: 0 (off) or 1 (on).

:DISPlay[:WINDow]:TEXT[:Data] <quoted string>

This command displays a message on the front panel. The power supply will display up to 16 characters and all the rest will be truncated. The string can be

sent between simple or double quotes.

:DISPlay[:WINDow]:TEXT[:DATA]?

This command queries the displayed message. It returns a quoted string of maximum 16 characters.

:DISPlay[:WINDow]:TEXT:CLEar

This command clears the message displayed on the front pannel. Only indicators will be displayed

MEASure Subsystem

This subsystem contains commands that allow you to measure the current and voltage to the output terminals of the power supply.

:MEASure:CURRent[:DC]?

This command queris the current measured to the output terminals of the power supply.

:MEASure[:VOLTage][:DC]?

This command queries the voltage measured to the output terminals of the power supply.

Important note! VOLT? Command returns previously programmed voltage level.

MEAS[:VOLT][:DC]? Command returns voltage measured to the output terminals of the power supply.

CURR? Command returns previously programmed current value. MEAS:CURR[:DC]? Command returns the measured current to the output terminals of the power supply.

MEMory Subsystem

This subsystem contains commands that manage power supply’s memory locations.

MEMory:STATe:NAME <numeric value>,<quoted string>

This command allows you to name a memory location. The numeric value parameter gives the number of the memory location that

will be named. It can be between 0 and 99. The quoted string contains the name of the location. The name can be sent

between simple or double quotes and it can have up to 10 characters. When delivered, the power supply has 99 locations free and one location ocupied (power_up state is saved in location 0). Free locations have no name

when the power supply is delivered (the name is 10 space characters). The state name is saved in the non-volatile memory. Location 0 (power_up state) cannot be renamed. The rest of the locations can

all be renamed, without notice.

MEMory:STATe:NAME? <numeric value>

This command queries the nameof the specified location.

OUTPut Subsystem

This subsystem controls the output of the power supply.

:OUTPut[:STATe] {0|1|OFF|ON}

This command enables and disable s the output of the power supply. You can replace off | on parameters with 0 | 1 numeric values.

When output is enabled, the power supply will display voltage and current value measured on the output terminals of the power supply. When output is disabled, the power supply will display Output Off message

and the indicators according to power supply’s state. When output is disabled, output voltage is 0 V and the current is 0.002 A. When delivered, after power on reset, output will be disabled (it depends on the

parameters saved in power_up location).

OUTPut[:STATe]?

This command queries the output state of the power supply. It returns only numeric values: 0 (for off state) or 1 (for on state)

SOURce Subsystem

According to SCPI standard, SOURce node is optional, so the devices which are primarily sources accept shorter commands.

This subsystem contains commands that program power supply parameters or commands that query programmed power supply parameters (for example:

programmed values for current and voltage, programmed values for step current and step voltage, lowest or highest value possible to program for current and voltage etc. )

:CURRent[:LEVel][:IMMediate][:AMPLitude] {<current>|MIN|MAX|UP|DOWN}

This command allows you to set the current value to the output of the power supply.

Instead of a numeric value, you can use MIN or MAX, UP or DOWN parameters. MIN allows you to set the lowest current value, which is 0 A.

MAX allows you to set the highest possible current value for model you have. With UP or DOWN parameters, this command allows you to increase / decrease the output value of the current with a preset value (the step you set with :CURRent:STEP {< numeric value>|DEFault} command, or the default

step of the power supply). The power supply does not allow you to increase over the maximum allowed

value for this parameter or to decrease above the minimum allowed value of this parameter (when the minimum/maximum value is reached, the power supply does not decrease/increase that value anymore).

:CURRent[:LEVel][:IMMediate][:AMPLitude]? [MIN|MAX]

This command queries the programmed current level. MIN and MAX parameters are optional. When using MIN or MAX parameters, the power supply returns the lowest or the highest value that are possible to

program for current, depending on the parameter.

:CURRent[:LEVel][:IMMediate]:STEP[:INCrement] {<numeric value>|DEFault}

This command allows you to set the current step for CURR UP or CURR DOWN command. The default value for current step is 1 mA.

:CURRent[:LEVel][:IMMediate]:STEP[:INCrement]? [DEFault]

This command queries the programmed current step value (if no parameter specified), or the default current step value (if DEFault parameter is specified

within the command). The returned value is specified in Amps.

Example: Here is an example of how you program current step value and how you increase / decrease current output value using step.

CURR:STEP 0.2 ;program current step value

CURR UP ;increase output current

CURR:STEP 0.5 ;program current step value CURR DOWN ;decrease output current

Note: If no step value was programmed before CURR UP or CURR

DOWN commands, default step value (0.001 A) will be used.

CURRent[:LEVel][:IMMediate]:TRIGgered[:AMPLitude] {<current>|MIN|MAX}

This command allows you to program the current trigger value, which is transfered to the output terminals when a trigger signal occurs.

By programming this value, you don’t change the current programmed value. Instead of a numeric value, you can use MIN or MAX parameters.

MIN allows you to set the lowest current value, which is 0 V. MAX allows you to set the highest possible current value for model you have.

:CURRent[:LEVel][:IMMediate]:TRIGgered[:AMPLitude]? [MIN|MAX]

This command queries the programmed current trigger level. When using MIN or MAX parameters, the power supply returns the lowest or the highest value allowed for current trigger parameter.

:VOLTage[:LEVel][:IMMediate][:AMPLitude] {<voltage>|MIN|MAX|UP|DOWN}

This command allows you to set the voltage value to the output of the power supply.

Instead of a numeric value, you can use MIN or MAX, UP or DOWN parameters.

MIN allows you to set the lowest voltage value, which is 0 V. MAX allows you to set the highest possible voltage value for model you have. With UP or DOWN parameters, this command allows you to increase /

decrease the output value of the voltage with a preset value (the step you set with :VOLTage:STEP {<numeric value>|DEFault} command, or the default

step of the power supply). The power supply does not allow you to increase over the maximum allowed

value for this parameter or to decrease above the minimum allowed value of this parameter (when the minimum/maximum value is reached, the power

supply does not decrease/increase that value anymore).

:VOLTage[:LEVel][:IMMediate][:AMPLitude]? [MIN|MAX]

This command queries the programmed voltage level. When using MIN or MAX parameters, the power supply returns the lowest or the highest value that

is possible to program for voltage, depending on the parameter.

:VOLTage[:LEVel][:IMMediate]:STEP[:INCrement] {<numeric value>|DEFault}

This command allows you to set the voltage step for VOLT UP or VOLT DOWN command. The default value for voltage step is 10 mV.

:VOLTage[:LEVel][:IMMediate]:STEP[:INCrement]? [DEFault]

This command queries the programmed voltage step value (if no parameter specified), or the default voltage step value (if DEFault parameter is specified within the command) for voltage. The returned value is specified in Volt.

Example: Here is an example of how you program voltage step value and how you increase / decrease voltage output value using step.

VOLT:STEP 0.2 ;program voltage step value VOLT UP ;increase output voltage

VOLT:STEP 0.5 ;program voltage step value VOLT DOWN ;decrease output voltage

Note: If no step value was programmed before VOLT UP or VOLT DOWN commands, default step value (0.010 V) will be used.

:VOLTage[:LEVel][:IMMediate]:TRIGgered[:AMPLitude] <current>|MIN|MAX}

This command allows you to program the voltage trigger value, which is transfered to the output terminals when a trigger signal occurs.

By programming this value, you don’t change the voltage programmed value. Instead of a numeric value, you can use MIN or MAX parameters.

MIN allows you to set the lowest voltage value, which is 0 V. MAX allows you to set the highest possible voltage value for model you have.

:VOLTage[:LEVel][:IMMediate]:TRIGgered[:AMPLitude]? [MIN|MAX]

This command queries the programmed voltage trigger level. When using MIN or MAX parameters, the power supply returns the lowest or the highest value

allowed for voltage trigger value, depending on the parameter.

:VOLTage:PROTection[:LEVel] {<voltage>|MIN|MAX}

This command allows you to set the voltage level at which the overvoltage protection circuit will be activated. If the output voltage will get equal or greater than the programmed OVP level, then the power supply will have

output voltage value 0 V (output is disabled).

:VOLTage:PROTection[:LEVel]? [MIN|MAX]

This command queries the programmed voltage protection level. When using MIN or MAX parameters, the power supply returns the lowest or the highest

value that is possible to program for voltage protection level, depending on the parameter.

:VOLTage:PROTection:STATe {0|1|OFF|ON}

This command allows you to disable / enable the overvoltage protection circuit. After power on reset, the overvoltage protection circuit is enabled and the

programmed OVP value depends on the model you have.

:VOLTage:PROTection:STATe?

This command queries the overvoltage protection circuit state. The returned parameter is always a numeric parameter: 0 (for OFF state) or 1 (for ON state).

:VOLTage:PROTection:TRIPped?

This command queries if the protection circuit is tripped or not. The returned parameter is always a numeric parameter:. 0 for OVP circuit not tripped or 1 for

OVP circuit tripped.

:VOLTage:PROTection:CLEar

This command allows you to clear the overvoltage protection circuit and it does not affect the programmed voltage trip level.

After this command the power supply returns to the previous state (output voltage will have the same value as before OVP was enabled). In this case,

before you clear the protection circuit, you must lower the output voltage below OVP trip level or increase the OVP trip level above the output voltage value.

Here are some examples of how you work with overvoltage protection circuit using remote interface commands:

Example 1: Here is an example of how you program the overvoltage protection circuit using remote interface commands:

VOLT:PROT 5 ;set OVP trip level at 5V VOLT:PROT? ;responds with programmed OVP trip level (5V)

VOLT:PROT:STAT ON ;enable OVP circuit VOLT:PROT:STAT? ;responds with OVP circuit state (1)

VOLT:PROT:TRIP? ;responds if OVP circuit is tripped

;(0 if output voltage lower than OVP trip

;level and 1 otherwise)

OVP circuit is enabled . If output voltage becomes equal or greater than OVP programmed trip level, OVP circuit trips and Over Voltage and

Output Off messages will be displayed. Output voltage will become 0 V.

It is not necessary to check every setting with the interogative command! This is an example of how you use this commands.

Example 2: Here is an example of how you clear the overvoltage condition by increasing OVP trip level, using remote interface commands:

Let’s say that the output voltage is lower than 5V. No load connected.

VOLT:PROT 5 ;program OVP trip level VOLT:PROT:STAT ON ;enable OVP circuit

If OVP circuit is already enabled, you don’t have to enable it again!

VOLT 6 ;OVP circuit tripped

When output voltage becomes equal or greater than OVP trip level (here is 5V), OVP circuit trips. Output is disabled and Over Voltage and Output Off messages will be displayed. Output voltage becomes 0 V.

VOLT:PROT 6.5 ;increase OVP trip level Still output is disabled and Over Voltage message is displayed (because

you didn’t clear OVP condition yet)

VOLT:PROT:CLEAR ;clear OVP condition

Power supply returns to previous state before enabling OVP circuit. It will display 6V and 0A. Since you didn’t disable OVP circuit, ovp

indicator will be displayed.

Example 3: Here is an example of how you clear the overvoltage condition by decreasing output voltage level, using remote interface commands:

Let’s say that the output voltage is lower than 10V. No load connected.

VOLT:PROT 10 ;program OVP trip level VOLT:PROT:STAT ON ;enable OVP circuit

If OVP circuit is already enabled, you don’t have to enable it again!

VOLT 10 ;OVP circuit tripped

When output voltage becomes equal or greater than OVP trip level (here is 10V), OVP circuit trips. Output is disabled and Over Voltage message

will be displayed.

VOLT 5.5 ;decrease output voltage level VOLT? ;returns programmed output voltage (5.5V)

Still output is disabled and Over Voltage message is displayed (because you didn’t clear OVP condition yet)

VOLT:PROT:CLEAR ;clear OVP condition

Power supply returns to previous state before enabling OVP circuit. It will display 5.5V and 0A. Since you didn’t disable OVP circuit, ovp

indicator will be displayed.

Example 4: Here is an example of how you clear the overvoltage condition by disabling OVP circuit, using remote interface commands:

Let’s say that the output voltage is lower than 7V. No load connected.

VOLT:PROT 8 ;program OVP trip level VOLT:PROT:STAT ON ;enable OVP circuit

If OVP circuit is already enabled, you don’t have to enable it again!

VOLT 15 ;OVP circuit tripped

When output voltage becomes equal or greater than OVP trip level (here is 8V), OVP circuit trips. Output is disabled and Over Voltage message

will be displayed.

VOLT:PROT:STAT OFF ;Disable OVP circuit

Attention: if you have anything connected to the output terminals of the power supply, it it strongly recommended that you disconnect it before

disabling OVP circuit (because you don’t change output level and this it may harm your connected circuitry)

VOLT:PROT:STAT? ;returns OVP circuit state (0 – off state)

Still output is disabled and Over Voltage message is displayed (because you didn’t clear OVP condition yet)

VOLT:PROT:CLEAR ;clear OVP condition

Power supply returns to previous state before enabling OVP circuit. It will display 15V and 0A. Since you disabled OVP circuit, ovp indicator

will not be displayed anymore, until you enable OVP circuit again.

STATus Subsystem

This subsystem controls SCPI defined status reporting structures.

STATus:QUEStionable:EVENt?

This command queries Status Questionable Even Register. The power supply returns a decimal value which is the binary weighted sum of all bits of the

STATus:QUEStionable:ENABle <enable value>

This command sets Status Questionable Enable Register. This is a mask register.

If a bit of this register is set, the coresponding bit of Standard Event Register is reported to Status Byte Register.

STATus:QUEStionable:ENABle?

This command queries Status Questionable Enable Register. The power supply

returns a decimal value which is the binary weighted sum of all bits of the register.

SYSTem Subsystem

This subsystem contains functions that are not directly related to power supply performance.

:SYSTem:BEEPer[:IMMediate]

This command determines the power supply to generate a beeper right after she received this command.

SYSTem:COMMunicate:GPIB:RDEVice:ADDRess <numeric value>

This command will change the power supply’s GPIB address.

SYSTem:COMMunicate:GPIB:RDEVice:ADDRess?

This command queries the power supply’s GPIB address.

:SYSTem:ERRor?

This command queries t he power supply’s error queue. Errors are retrieved in a first-in-first-out order, so the first generated error is the first read error.

The error queue can store up to 20 errors. If more errors will be generated, the last error is overwritten and on the last position will be written – 350 error (queue overflow). No more errors will be stored until the queue is cleared (but

they are generated). The power supply will return error number followed by error definition. When all the errors were read, err indicator will not be displayed anymore and

error queue is empty. Sending this command now, determines the power supply to respond with No errors message.

SYSTem:INTERFACE GPIB|RS232

This command will select an interface, which becomes the active interface. The next command must be sent over the new active interface.

:SYSTem :VERSion?

This command queries the SCPI version number for which the instrument complies. The response is a string in the form YYYY.V, where YYYY represents the year version and V represents the approved revision number for that year

(for example, 1990.0).

TRIGger Subsystem

The power supply has a trigger subsystem, so voltage and current values can be changed when receiving a trigger signal. Depending on the trigger source selected, this change takes place immediately

(when receiving the trigger signal), or after a time period equal with the delay you set (a time period from the moment the power supply receives the trigger signal)

To activate the trigger subsystem you must follow the steps described bellow:

1. Specify the source of the trigger signal. The power supply accepts

a bus trigger or an immediate trigger coming from the remote

interface.

Bus trigger source

*TRG command is considered the trigger signal. The current and voltage trigger values become the output programmed values

after a time period (from the moment the power supply received the trigger signal), called trigger delay.

The trigger subsystem must be initiated before sending the trigger signal (for initiation you mus use the INITIATE command). Otherwise, -211 error is generated (trigger ignored error).

Immediate trigger source

INITIATE[:IMMEDIATE] command is considered the trigger signal. The current and voltage trigger values become the output programmed values

immediately after receiving INITIATE command. In this situation, *TRG command is ignored (the power supply doesn’t do anything and it doesn’t generate any errors).

After an interface reset or after power on reset, bus trigger source is selected.

2. Program the volt:trig and curr:trig values.

When receiving the trigger signal, the power supply transfers these values to volt and current programmed values immediatly (if imm trigger source is

selected) or after a period of time equal to the trigger delay programmed value (if bus trigger source is selected).

At power on reset or *RST command, voltage and current trigger values are the programmed values (values displayed in limit mode) until you explicitly program them with the desired values.

So before programming voltage and current values,

:VOLTage[:LEVel][:IMMediate]:TRIGgered[:AMPLitude]?and :CURRent[:LEVel][:IMMediate]:TRIGgered[:AMPLitude]?

commands return the programmed values for voltage and current.

Trigger programmed values are available until a new programming command for a certain parameter, no matter how many times you use the trigger

subsystem.

If voltage and current trigger values are programmed, they do not change when you change the output voltage and current values.

3. Program the trigger delay value.

Set the time delay between the trigger signal recognition and the changes the power supply must execute according to the settings of the trigger subsystem.

This value is not considered if IMMEDIATE trigger source is selected.

The programmed value is available until a new programming command for delay parameter, no matter how many times you use the trigger subsystem.

At power on reset or *RST command the trigger delay value is 0.

Important note!

These steps may be executed in any order you want, but before initiating the trigger subsystem.

4. Initiate the trigger subsytem.

Trigger subsystem is initiated using INITiate[:IMMediate] command. If IMM trigger source is selected, voltage and current trigger values become the

output values immediately. If BUS trigger source is selected, voltage and trigger values become the output values after a delay period from the moment the power supply received the

triger signal (*TRG command). It is important to initiate the trigger subsystem before sending the trigger signal. Otherwise, Trigger ignored error (err -211) is generated.

Here are described the commands used to set trigger subsystem’s parameters:

:CURRent[:LEVel][:IMMediate]:TRIGgered[:AMPLitude] <current>|MIN|MAX}

This command allows you to program the current trigger value, which is transfered to the output terminals when a trigger signal occurs.

By programming this value, you don’t change the current programmed value. Instead of a numeric value, you can use MIN or MAX parameters. MIN allows you to set the lowest current value, which is 0 V.

MAX allows you to set the highest possible current value for model you have.

:CURRent[:LEVel][:IMMediate]:TRIGgered[:AMPLitude]? [MIN|MAX]

This command queries the programmed current trigger level. When using MIN or MAX parameters, the power supply returns the lowest or the highest value allowed for current trigger parameter.

:VOLTage[:LEVel][:IMMediate]:TRIGgered[:AMPLitude]{<current>|MIN|MAX}

This command allows you to program the voltage trigger value, which is transfered to the output terminals when a trigger signal occurs. By programming this value, you don’t change the voltage programmed value.

Instead of a numeric value, you can use MIN or MAX parameters. MIN allows you to set the lowest voltage value, which is 0 V. MAX allows you to set the highest possible voltage value for model you have.

:VOLTage[:LEVel][:IMMediate]:TRIGgered[:AMPLitude]? [MIN|MAX]

This command queries the programmed voltage trigger level. When using MIN or MAX parameters, the power supply returns the lowest or the highest value

allowed for voltage trigger parameter.

:INITiate[:IMMediate]

This command initiates the trigger subsystem. If immediate trigger source is selected, trigger programmed values become the output values immediately.

If bus trigger source is selected, trigger programmed values become the output values after the trigger delay period from the moment the power supply received the trigger signal

:TRIGger:DELay {<seconds> | MIN | MAX}

This command allows you to set the trigger delay value in seconds. This is the time delay between the receive of the trigger signal and the

corresponding action (trigger values become the output values). Instead of a numeric value, you can use MIN or MAX parameters. MIN parameter allows you to set the trigger delay to 0 seconds.

MAX parameter allows you to set the trigger delay to 36,000 seconds (equivalent to 10 hours). At power on reset or after *RST command this value is set to 0 seconds.

:TRIGger:DELay? [MIN | MAX]

This command queries the trigger delay programmed value. When using MIN or MAX parameters, the power supply returns the lowest and the highest value

that are possible to program for trigger delay.

:TRIGger:SOURce {BUS | IMMediate}

This command allows you to select the tr igger source from which the power supply accepts the trigger signal.

The power supply accepts an immediate trigger or a bus trigger. After power on reset or *RST command bus trigger source is selected.

;TRIGger:SOURce?

This command queries the seleted trigger source. Power supply returns BUS or IMM message, depending on the selected trigger source.

*TRG

This command generates the trigger signal for the trigger subsystem, if BUS trigger source is selected.

Important note!

If bus trigger source is selected and trigger delay parameter value is greater than zero, the power supply will not accept other interface command until delay

value is passed and trigger values become the output programmed values.

While in remote mode, the only active key is Remote/Local key. If pressing this key while delay trigger is passing, the power supply will transfer trigger

values to the output programmed values immediately, no matter what trigger delay value is programmed. The power supply will go to local mode.

Trigger subsystem parameters (voltage trigger value, current trigger value, trigger delay value, trigger source) are saved, too, when saving the current

state.

Non-SCPI Commands

SET {<voltage>|DEF|MIN|MAX}[,<current>|DEF|MIN|MAX]

This is a non-SCPI command. This command allows you to program output voltage and current values in the

same time, using one command only. Using this command, you can program output voltage or output voltage and

current values. So if you specify one parameter only, it is considered as voltage programming value. Instead of using numeric parameters for current and voltage values, you can use

DEFault, MIN or MAX parameters. For more information about these parameters, please refer to Technical Specifications section, programming ranges tables.

SET?

This command queries voltage and current programmed values. The power supply returns both values in a single string (voltage value first):

+1.000000E+01,+5.000000E+00

CALibration:MESSAGE <quoted string>

This command allows you to store some informations about the power supply (e.g.: power supply’s serial number, last calibration date, service information etc)

Calibration message may contain up to 40 characters and it is stored in a nonvolatile memory.

CALibration:MESSAGE?

This command queries calibration message. You can write this message only over the remote interface, but you can view it

using Errors / Calibrate key when in local mode. For more informations you can refer to Local Mode Operation, Errors / Calibrate key section.

SYSTem:REMote

This command is used to place the power supply in remote mode (the power supply receives commands over RS-232 interface).

If commands are sent over the RS-232 interface without placing the power supply in remote mode, Power supply in local mode mes sage is sent to PC.

If the command is sent over GPIB interface, Err 510, Command allowed only in RS232 is generated.

IEEE 488.2 Commands

The 488.2 specifications include some instrument commands and a status information scheme. For more information about SCPI Status Registers, see Status Reporting

Overview section.

*CLS (Clear Status)

This command clears Status Byte Register and all the Event Registers summarized in Status Byte, such as Questionable Status Event Register and

Standard Event Register.

*ESE <enable value> (Standard Event Status Enable)

This command allows you to set Standard Event Enable Register with a decimal value between 0 and 255. If a bit of this register is set, the coresponding bit of Standard Event Register

is reported to Status Byte Register.

*ESE?

This command queries the Standard Event Enable Register value. The power supply returns a decimal value between 0 and 255, which is the binary weighted sum of all bits of the register.

*ESR? (Event Status Register)

This command queries the Standard Event Register value. The power supply returns a decimal value between 0 and 255, which is the

binary weighted sum of all bits of the register. After sending this value, Standard Event Register is cleared.

*IDN? (Identification)

This command queries the identification string of the power supply. The identification string has four fields: the first field is manufacturer’s name,

the second field is model number (depending on the model number of the power supply), the third fie ld is serial number (always 0), the fourth field is firmware revision level (first number indicates firmware revision number for

main processor and the second number indicates firmware revision number for communication processor). For 9121 model, t he power supply returns a string with the following format:

S.C. CODEC S.R.L. ROMANIA, 9121 , 0, 1.0_1.0

*OPC (Operation Complete)

This command sets bit 0 (Operation Complete bit) from the Standard Event Register when the power supply completes all operations, including *OPC command.

*OPC?

The power supply returns an ASCII “1” after all operations, including this command are executed.

*RST

This command allows you to reset the power supply. The power supply reset can be achieved by sending this command or by selecting RESET option from the Recall menu (Recall key).

The power supply reset values for different parameters are listed in Technical Specifications section.

*SAV {0 | 1 | 2 | … | 99}

This command saves the current state of the power supply in the specified location.

Stored parameters are: voltage limit, step voltage, overvoltage protection level, current limit, step current, voltage trigger value, current trigger value, trigger delay value, trigger source, stored state name, state of overvoltage protection

circuit, state of display, output state.

The saved states are kept in a non -volatile memory, so they won’t be lost when turning off the power supply.

A state location can be overwritten without any notification from the power supply.

*RCL {0 | 1 | 2 | … | 99}

This command recalls the specified state so this state becomes the current operating state.

When delivered from the fcatory, the memory locations are empty.

*SRE <enable value> (Service Request Enable)

This command allows you to set Status Byte Enable Register with a decimal value between 0 and 255.

*SRE?

This command queries the Status Byte Enable Register. The power supply returns a

decimal value, which is the binary weighted sum of all bits of the register.

*STB? (Status Byte)

This command queries Status Byte register. The power supply returns a decimal value between 0 and 255.

*TRG

This command is the trigger signal when bus trigger source is selected.

IEEE 488 Bus Commands

These comands are GPIB / 488 interface specific commands. In command mode (ATN line low), the power supply can receive three classes of commands:

Talk and Listen addresses: They define which device from GPIB interface will be the active Talker and which devices will be the active Listeners. When ATN

line is true, all devices must wait for the commands: listeners an talker will be assigned.

Universal commands: they are commands sent by the Controller to all devices from GPIB interface. The universal commands consist of:

commands sent using general bus management lines. They are called

uniline commands. For more information, please refer to General bus management lines section.

commands encoded as bytes. They are sent over DIO lines, so they are

called multiline commands.

DCL (Device Clear) Resets the power supply to its default state. This command is equivalent to

the *RST command, so the power supply will go to reset state.

LLO (Local Lockout)

Disables front panel keys, including Remote/Local key (which allows you to put the power supply in local mode). The power supply settings can no longer be changed from the front panel.

SPE (Serial Poll Enable)

Tells the addressed Talker to send a status byte. This byte gives informations about the device to the Controller.

For more information about Status Byte, please refer to SCPI Status Registers section.

For more information about Serial Poll, please refer to Serial Poll Procedure section.

SPD (Serial Poll Disable)

Disables Serial Poll procedure. For more information about Serial Poll, please refer to Serial Poll Procedure section.

Addressed commands: they are byte commands sent by the Controller only to the addressed Listeners. So these commands are sent with address bytes.

GET (Groupe Execute Trigger)

This command is equivalent to the *TRG command. For more

information about trigger subsystem of the power supply, please refer

to Trigger Subsystem section.

SDC (Selected Device Clear)

Resets the power supply to its default state. This command is

equivalent to the *RST command, so the power supply will go to reset

state.

GTL (Go To Local)

The power supply will go to local mode. It will receive commands

only from front panel.

ASCII Table For GPIB

Ch Ctrl Cmd Dec Hex Ch Cmd Dec Hex

NUL ^ @ 0 0 Sp L0 32 20 SOH ^ A GTL 1 1 ! L1 33 21

STX ^ B 2 2 “ L2 34 22 ETX ^ C 3 3 # L3 35 23 EOT ^ D SDC 4 4 $ L4 36 24 ENQ ^ E PPC 5 5 % L5 37 25

ACK ^ F 6 6 & L6 38 26

BEL ^ G 7 7 ‘ L7 39 27

BS ^ H GET 8 8 ( L8 40 28

HT ^ I TCT 9 9 ) L9 41 29

LF ^ J 10 a * L10 42 2a

VT ^ K 11 b + L11 43 2b

FF ^ L 12 c , L12 44 2c

CR ^ M 13 d -- L13 45 2d

SO ^ N 14 e . L14 46 2e

SI ^ O 15 f / L15 47 2f

DLE ^ P 16 10 0 L16 48 30

DC1 ^ Q LLO 17 11 1 L17 49 31

DC2 ^ R 18 12 2 L18 50 32

DC3 ^ S 19 13 3 L19 51 33

DC4 ^ T DCL 20 14 4 L20 52 34

NAK ^ U PPU 21 15 5 L21 53 35

SYN ^ V 22 16 6 L22 54 36

ETB ^ W 23 17 7 L23 55 37

BS ^ H SPE 24 18 8 L24 56 38

HT ^ I SPD 25 19 9 L25 57 39

LF ^ J 26 1a : L26 58 3a

VT ^ K 27 1b ; L27 59 3b

FF ^ L 28 1c < L28 60 3c

CR ^ M 29 1d = L29 61 3d

SO ^ N 30 1e > L30 62 3e

SI ^ O 31 1f ? UNL 63 3f

Ch Cmd Dec Hex Ch Cmd Dec Hex

@ T0 64 40 ‘ SC0 96 60

A T1 65 41 a SC1 97 61

B T2 66 42 b SC2 98 62 C T3 67 43 c SC3 99 63

D T4 68 44 d SC4 100 64

E T5 69 45 e SC5 101 65 F T6 70 46 f SC6 102 66

G T7 71 47 g SC7 103 67

H T8 72 48 h SC8 104 68

I T9 73 49 i SC9 105 69

J T10 74 4a j SC10 106 6a

K T11 75 4b k SC11 107 6b

L T12 76 4c l SC12 108 6c

M T13 77 4d m SC13 109 6d

N T14 78 4e n SC14 110 6e O T15 79 4f o SC15 111 6f

P T16 80 50 p SC16 112 70

Q T17 81 51 q SC17 113 71

R T18 82 52 r SC18 114 72 S T19 83 53 s SC19 115 73

T T20 84 54 t SC20 116 74 U T21 85 55 u SC21 117 75 V T22 86 56 v SC22 118 76

W T23 87 57 w SC23 119 77

X T24 88 58 x SC24 120 78 Y T25 89 59 y SC25 121 79

Z T26 90 5a z SC26 122 7a

[ T27 91 5b { SC27 123 7b \ T28 92 5c | SC28 124 7c ] T29 93 5d } SC29 125 7d

^ T30 94 5e ~ SC30 126 7e

_ UNT 95 5f DEL SC31 127 7f

The SCPI Status Regist ers

Status reporting scheme is described in this section.

Voltage

Not Used

Overvolt

Not Used

OPC

Not Used

QYE

DDE

EXE

CME

Not Used

PON

Current

Standard Event

Event Register

Enable Register

Questionable Status

Event Register

Enable Register Not Used

Not Used

QUES

MAV

ESB

RQS

Not Used

Output Buffer

Status Byte

Summary Reg Enable Reg

Event Register is a read only register. Bits in an event register are set depending on the state of the power supply.

An event register is cleared after its value was queried or by sending *CLS command.

A *RST command does not clear event registers. When an event register is queried, the power supply returns a decimal value,

which is the binary – weighted sum of all bits of the register. An Enable Register defines which bits from the corresponding event register

are logically Ored to form the coresponding bit in the Status Byte. An enable register is readable and writable. An enable register is not cleared after quering it, or by *CLS command.

Questionable Status Register

The Questionable Status Register contains bits which give an indication of the quality of different parameters. A set bit indicates that the associated parameter

is of questionable quality.

Bit 0 -Voltage

- is set when the voltage becomes unregulated.

- indicates that the power supply is / was in constant current mode

Bit 1 -Current

- is set when the current becomes unregulated.

- indicates that the power supply is / was in constant voltage mode

Bits 2..8 -Not used

- always set to 0

Bit 9 -Overvoltage

- is set when over voltage protection circuit has tripped

Bits 10..15 -Not used

- always set to 0

Questionable Status Event Register is cleared by:

*CLS command

quering event register, using STATus:QUEStionable? Command

Questionable Status Enable Register is cleared by:

STATus:QUEStionable:ENABle 0 command

Standard Event Register

Standard Event Register reports different instrument events, such as: query errors, device dependent error, execution errors, command errors, power on

event. A set bit indicates that an event of the specified type occurred.

Bit 0 - OPC (Operation Complete)

- indicates that all previous commands have been executed and the device is ready to accpet new commands

- this bit is set only after an *OPC command

Bit 1 - Not used

- always set to 0

Bit 2 - QYE (Query Error)

Bit 3 - DDE (Device Dependent Error)

- indicates that a device dependent (user defined) error has occurred,

such as self test errors, or calibration errors

Bit 4 - EXE (Execution Error)

- indicates that an execution error occured

Bit 5 - CME (Command Error )

- indicates that a command error occured

Bit 6 - Not used

- always set to 0

Bit 7 - PON (Power On)

indicates that the power supply was turned off and on since the last time

Standard Event Register was cleared or read.

Standard Event Register is cleared by:

*CLS command

quering event register, using *ESR? Command

Standard Event Enable Register is cleared by:

*ESE 0 command

Status Byte Register

Status Byte Register reports conditions from the defined status registers, depending on the bits from the enable registers. So clearing an event register

will clear the coresponding bits from the Status Byte Register.

Bits 0..2 - Not used

- always set to 0

Bit 3 - QUES

- indicates that one or more bits are set in questionable status register (and the corresponding bits in the enable register are set, too)

Bit 4 - MAV (message available)

- indicates that there is data in the output buffer

Bit 5 - ESB

- indicates that one or more bits sre set in standard event register (and

the corresponding bits in the enable register are set, too)

Bit 6 - RQS

- all the bits from the Status Byte register which have the

corresponding bit from the Status Byte Enable Register set, are logically Ored. The res ult is kept in RQS bit.

Bit 7 - Not used

- always set to 0.

Status Byte Register is cleared by:

*CLS command

quering Standard Event Register, using *ESR? Command will clear bit 5 in

Status Byte Register

Status Byte Enable Register is cleared by:

*SRE 0 command

Error Messages

There are 2 kinds of errors that will be generated by the power supply:

♦ standard errors (errors defined by SCPI standard, in [-299,-100] interval) ♦ device specific errors (user defined errors, in [-399,-300] or [1,32767]

interval)

Following types of errors may occur:

♦ Command errors (defined by SCPI standard) ♦ Execution errors (defined by SCPI standard) ♦ Device-specific errors (defined by SCPI standard)

♦ Self test errors (device specific errors, user defined) ♦ Calibration errors (device specific errors, user defined)

Command Errors

Error - 101: Invalid character

An invalid character was received in the command string, within the parameter

Error - 102: Syntax error

The command string is not in syntactically correct (*, : in the wrong place)

Error - 103: Invalid separator

Wrong separator between commands in the same command string.

Error - 108: Parameter not allowed

More parameters than expected were received for the header

Error - 109: Missing parameter

Fewer parameters than required were received for the header

Error - 113: Undefined header

The received header was not defined for this device

Error - 114: Header suffix out of range

The value for the numeric suffix attached to the program mnemonic is not correct. The device recognizes only the default header suffix (which is 1).

Error - 121: Invalid character in number

An invalid character was received within the numeric parameter (or within the suffix).

Error -123: Exponent too large

The numeric parameter received has an exponent larger than 32,000.

Error -124: Too many digits

The decimal numeric parameter has a mantissa which contains more than 255 digits, excluding leading zeros

Error - 128: Numeric data not allowed

A legal numeric data element was received, but is not the right data element for the header

Error -131: Invalid suffix

The received suffix for the numeric parameter is not specified for this device.

Error - 138: Suffix not allowed

This numeric parameter does not accept a suffix.

Error - 141: Invalid character data

The character data element contains an invalid character.

Error - 148: Character data not allowed

A descrete parameter was received but a character string or a numeric parameter was expected.

Error - 151: Invalid string data A string data element was expected, but it was invalid for some reason (it didn’t start/stop with simple/double quotes).

Error - 158: String data not allowed

A legal string data element was received, but it is not the right data element for the header.

Execution Errors

Error – 211: Trigger ignored

*TRG command was received, but it was ingnored because trigger subsystem was not initiated (using INITiate command).

Error - 222: Data out of range

The numeric parameter value is out of range.

Error - 223: Too much data

A legal string program data element contains more data than the device could handle due to memory or due to device specific requirements.

Error - 224: Illegal parameter data value

A legal type of parameter was received, but it is not the expected parameter for the header.

Device Specific Errors

Error - 350: Queue overflow

Queue error is full, more than 20 errors occurred. No more errors will be saved until error queue will be erased.

Error - 361: Parity error in program message

Parity bit not correct when data received over the RS-232 interface

Error – 362: Framing error in program message

Stop bit not detected when data received over the RS-232 interface (stop bit detected as clear)

Error – 363: Input buffer overrun

Hardware input buffer of the serial port overflows with data because of the improper reading of the buffer.

Error – 365: Time-out error

BK Precision 9120, 9123, 9121 Instruction Manual

Specifications and Main Features

Frequently Asked Questions

User Manual