The Model 228 Voltage/Current Source is both a constant
voltage and constant current source with front panel and
IEEE operation. The Model 228 can be used as a constant
voltage source or a constant current source. It has four
quadrant operation. This means that the voltage or current
sources can operate as a source or a sink in either positive
or negative polarities. Full power capability of 1OOW may be
obtained in any quadrant.
Parameter entry is done in one of two ways. Either using the
data keypad to enter the desired value into the display or
using the display modify function. The display modify
function allows the user to modify either display by
selecting a digit of the display and incrementing or
decrementing that digit with the appropriate keys. With the
carry, borrow and autorepeat capability, front panel
operation is flexible and easy to program. The user selects
the range with the decimal point.
The Model 228 has a 100 point data memory that allows the
user to store up to 100 unique values of current, voltage
and dwell time for future use. Once a particular level is
stored in the data memory, the user need not reprogram that
The output terminals are located on a quick disconnect board
that inserts into the rear panel of the mainframe. The
output is disconnected from the quick disconnect board when
it is removed from the mainframe.
The Model 228 includes the following features:
Six ranges that allow a wide variety of voltage/current
Seven front panel programs. The programs include:
Program 1 Copy for duplicating memory location information.
Program 2 Sink for sink only operation.
Program 3 IEEE for changing IEEE primary address.
Program 4 MOD V for modulating output voltage.
Program 5 MOD 1 for modulating output current.
Program 6 Test for Model 228 self test.
Program 9 Reset for resetting the Model 228 to factory set
values. See paragraph 3.13.7
Dual displays for easy reference of the instrument’s status.
The left display has two display modes (voltage and memory
step). The right display also has two display modes
amps and seconds).
Two methods of modifying the source or sink value: Data
entry from the data keypad, and increment or decrement of
displayed valued using the decade keys.
100 point data memory to store up to 100 unique values of
voltage, current and dwell time. Each location also includes:
sink mode status and voltage current modulation status.
All information stored in a memory location is battery
backed up. This means that if the instrument is powered
down, the stored information (voltage, current and dwell
time parameters) remains in a particular location until
changed by the user.
switch that places the output in
either the operate mode (displayed value is present at
output) or in the standby mode (output is programmed to
Compliance status is easy to read on the front panel
compliance graph. The graph shows the user at a glance how
the Model 228 is operating (source or sink polarity and
voltage or current compliance).
IEEE-488 bus operation is standard. This enables the Model
228 to be incorporated into a system that uses programmed
control over the IEEE-488 bus.
Single step, single cycle and continuous memory modes
control the sequence between data points in the 100 point
data memory. The program mode may be controlled in one
of three ways; using the front panel START/STOP key, the
external trigger pulse or by commands over the IEEE-488
Output terminals are located on the quick disconnect board
for optimum safety. The output terminals, the sense
terminals, current monitor terminals and the external
modulation terminals are also located on the quick
disconnect board. Several quick disconnect boards may be
wired with their own unique wiring ‘configuration. When one
configuration is required, simply insert into the mainframe.
In this way, cumbersome rewiring of one board is avoided.
Remote and Local Sensing. This allows the user to sense at
the output terminals or at the load or source. Remote
sensing compensates for the effects of the l*R lead drop by
maintaining regulation at the load instead of at the output
terminals of the Model 228.
Four Quadrant Operation. This means that the voltage or
current outputs can operate as a source or a load in either
positive or negative polarities. The front panel compliance
graph shows the user where the Model 228 is operating
(source or sink).