2470 High Voltage SourceMeter Instrument Reference Manual
Section 4: Sourcing and measuring
2470-901-01 Rev. A /
May
2019
4-17
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.
High-impedance output-off state
When the high-impedance output-off state is selected and the output is turned off:
•
The measurement sense is set to 2-wire
•
The output relay opens, disconnecting the instrument as a load
Opening the relay disconnects external circuitry from the inputs and outputs of the instrument. To
prevent excessive wear on the output relay, do not use this output-off state for tests that turn the
output off and on frequently.
The high-impedance output-off state should be used when the instrument is connected to a power
source or another source-measure instrument. In some cases, it may also be appropriate for devices
such as capacitors.
When the output is turned on again, the relay has a settling time of approximately 15 ms.
When the high-impedance output-off state is selected, you cannot make measurements using 2-wire
connections.
Zero output-off state
When the zero output-off state is selected and you turn off the output:
•
The measurement sense is changed to 2-wire
•
The voltage source is selected and set to 0
•
The range is set to the presently selected range (turn off autorange)
•
If the source is voltage, the current limit is not changed
•
If the source is current, the current limit is set to the programmed source current value or to 10%
full scale of the present current range, whichever is greater
When the zero output-off state is selected, you can use the instrument as an ammeter because it is
outputting 0 V.
