Section 2: General operation
Model 2450 Interactive SourceMeter® Instrument Reference Manual
2-82
2450-901-01 Rev. B/September 2013
Output-off state
Carefully consider and configure the appropriate output-off state, source, and limits before
connecting the Model 2450 to a device that can deliver energy, such as other voltage sources,
batteries, capacitors, or solar cells. Configure the settings that are recommended for the instrument
before making connections to the device. Failure to consider the output-off state, source, and limits
may result in damage to the instrument or to the device under test (DUT).
When the source of the instrument is turned off, it may not completely isolate the instrument from the
external circuit. You can use the output-off setting to place the Model 2450 in a known, noninteractive
state during idle periods, such as when changing the device under test. The output-off states that can
be selected for a Model 2450 are normal, high-impedance, zero, or guard.
When you change the output-off state, the selected output-off state is changed immediately. On
power-up, the instrument is momentarily in the high-impedance output-off state before going to the
selected output-off state.
Regardless of the selected output-off state, if an overtemperature condition or an interlock violation
occurs, the instrument goes into the high impedance output-off state.
When the output is off, the SOURCE area of the Home screen shows the source value that is set, not
the value that is presently being output.
Normal output-off state
When the Model 2450 is set to the normal output-off state, the following settings are made when the
source is turned off:
•
The measurement sense is set to 2-wire
•
The voltage source is selected and set to 0 V
•
The current limit is set to 10 percent of the full scale of the present current range
•
OUTPUT OFF is displayed in the Home page Source area
•
The Source button on the Home page shows the output that will be sourced when the output is turned
on again
Even though the voltage source is set to zero, the source value may not be exactly at zero and the
instrument may source or sink a small amount of power. In most cases, this source or sink power
level is insignificant. For passive devices such as resistors, normal mode should be sufficient to
protect your device. However, because the limit current is 10% of range, it may take time to remove
charge from large energy storage devices such as capacitors.
For sources, such as batteries, the normal output-off state limits the current to 10% of range. This
may be acceptable for devices such as another source-measure instrument or a power supply.
However, for devices such as small cell batteries, it can drain the batteries. In situations such as this,
use the high-impedance output-off state.
