Keithley 244 Instruction Manual page 14

ACCESSORIES
MODEL 244 HIGH VOLTAGE SUPPLY
Model 2441 Overload Protection Option
Description:
The Model 2441 when factory installed on the Model
244 provides automatic current limiting of the Model
244 output.
Specifications:
OVERLOAD: Model 2441 circuitry provides automatic
current limiting of the Model 244 when the over-
load input voltage to the Model 2441 exceeds
approximately +1.4 volts.
SENSITI"IT:T:
An overload input voltage from +1.4V
to +2.OV (+1.7 volts typically) will cause cur-
rent limiting of the Model 244 output.
OVERLOAD INDICATIONS:
The overload lamn will indi-
Typical Operation:
NOTE
The picaammeter (such as Model 414A) has a 1
volt output for full scale input on the range
selected.
If the current monitored by the
Model 414A increases to approximately 170% of
full scale the Model 414A output,of the 1.7
volts will activate the Model 2441 circuit.
Any
further increase in the current monitored
by the picoammeter will ultimately be limited
to no more than 200% of the full scale range
of the picoammeter. However current limiting
of the Model 244 will occur whenever the Model
244 output exceeds 11 milliamperes s the Model
2441 is activated.
cate whenever rhe Model 244 is in a current
limiting mode.
NOTE
The Model 244 will deliver a calibrated
voltage as long as the overload lamp is off
(or the overload input voltage does not
exceed +1.2 volts).
a. Connect the recorder output of a Keithley
picoammeter such as the Model 414A or equivalent to
the Overload Protection Input receptacle 5201. see
Figure 1.
b. Select the full scale current range an the
picoammeter for desired operating range.
c. Recorder output of 414A should be in 1 volt
NOISE IMMUNITY:
An 8V p-p at 60 Hz overload input
mode.
signal will not operate overload.
RESPONSE TIME: Time for a 2.5" Peak pulse to acti-
"ate 2441 is typically 0.25 seconds (lo-go%).
d. Operate the Model 244 as described in gecrion
2.
I
MODEL 244-2441
r-l
PICOAMMETER
MODEL 244-2441
PICOAMMETER
I
System
T Ground
FIGURE 6.
Overload Protection Connection Diagram.
10
0976