Model 930 Programmable Current Source
Features
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Description
The Model 930 is a programmable current source that
provides an output current that stays constant with changes
in load impedance. The output voltage will vary as necessary
to maintain the desired value of constant current through the
load. Output current of the Model 930 can be set by means
of an external potentiometer or by a DC voltage. It has an
internal regulator and reference circuit to make the output
current independent of power supply variations. Supply voltage
can be unregulated and can range from +12V to +32V. The
compliance voltage (maximum output voltage for highest
load impedance) is dependent on the supply voltage level and
is rated at the supply voltage less 5 Volts.
Program Output by Potentiometer Setting
or Voltage Input
Wide Supply Range from +12V to +32V
Fast Response from 10 碌s to Step Change
Well Regulated 10 megohms Output Impedance
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Operation
The Model 930 output current can be programmed by a 1000
ohm potentiometer or by a voltage input. To set the current
with a potentiometer, connect the potentiometer end terminals
across pins 1 and 7 and the wiper arm to pin 3. Connect pins
9, 10 and 11 to each other. This will provide a linear adjustment
of output current from 0.5 mA to 50 mA. This is extended to
a range of 5 mA to 500 mA on the 296HP Power Booster
Mounting Kit.
For voltage programming, the potentiometer must be removed
(pins 1, 3, 7 left open) and a jumper must be connected across
pins 3 and 4. As with potentiometer programming, pins 9, 10
and 11 must be connected together. When connected for
voltage programming, an input voltage of zero to +10V
provides a linear output current of +0.5mA to +50mA.
Need more output current? It鈥檚 easy, simply parallel the
outputs of several programmable current sources. For
example, the outputs of two Model 930/MK 296HP units can
be connected to the same load to provide a combined output
of up to one ampere.
FIGURE 1.
Model 930 Connected for Potentiometer Programming of I
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Output or Compliance Voltage
The key parameter in applying constant current sources is the
range of load impedance. This determines the range of output
voltage needed to maintain a constant current through the
varying load impedance. For example, if the load were to vary
from 1 ohm to 200 ohms and the desired constant current
were 50 mA, then the output voltage range needed would be
50 mV to 10V. The power supply must be 5 Volts greater than
the compliance voltage or 15 Volts, in this case.
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2401 Stanwell Drive
Concord, CA 94520-4841
(510) 687-4411 鈥?Fax (510) 687-3333
http://www.calex.com
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CALEX
FaxFACTS:
201
1997
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