Model DMM7510 7½ Digit Graphical Sampling Multimeter Reference Manual
Section 8: TSP command reference
DMM7510-901-01 Rev. B / May 2015
8-91
dmm.digitize.inputimpedance
This attribute determines when the 10 M
Ω
input divider is enabled.
Type
TSP-Link accessible
Affected by
Where saved
Default value
Attribute (RW)
Yes
Restore configuration
Instrument reset
Power cycle
Measure configuration list
Configuration script
Measure configuration list
dmm.IMPEDANCE_10M
Usage
setting
= dmm.digitize.inputimpedance
dmm.digitize.inputimpedance =
setting
setting
10 M
Ω
for all ranges:
dmm.IMPEDANCE_10M
Automatic:
dmm.IMPEDANCE_AUTO
Functions
dmm.FUNC_DC_VOLTAGE
dmm.FUNC_RESISTANCE
dmm.FUNC_ACV_FREQUENCY
dmm.FUNC_AC_VOLTAGE
dmm.FUNC_4W_RESISTANCE
dmm.FUNC_ACV_PERIOD
dmm.FUNC_DC_CURRENT
dmm.FUNC_DIODE
dmm.FUNC_DCV_RATIO
dmm.FUNC_AC_CURRENT
dmm.FUNC_CAPACITANCE
dmm.FUNC_DIGITIZE_CURRENT
dmm.FUNC_TEMPERATURE
dmm.FUNC_CONTINUITY
dmm.FUNC_DIGITIZE_VOLTAGE
Details
Automatic input impedance provides the lowest measure noise with the highest isolation on the
device under test (DUT). When automatic input impedance is selected, the 100 mV to 10 V voltage
ranges have more than 10
GΩ input impedance. For the 100 V and 1000 V ranges, a 10 MΩ input
divider is placed across the HI and LO input terminals.
When the input impedance is set to 10
MΩ, the 100 mV to 1000 V ranges have a 10 MΩ input divider
across the HI and LO input terminals. The 10
MΩ impedance provides stable measurements when
the terminals are open (approximately 100
μV at 1 PLC).
Choosing automatic input impedance is a balance between achieving low DC voltage noise on the
100 mV and 1 V ranges and optimizing measurement noise due to charge injection. The Model
DMM7510 is optimized for low noise and charge injection when the DUT has less than 100
KΩ input
resistance. When the DUT input impedance is more than 100 K, selecting an input impedance of
10
MΩ optimizes the measurement for lowest noise on the 100 mV and 1 V ranges. You can achieve
short-term low noise and low charge injection on the 100 mV and 1 V ranges with autozero off. For
the 10 V to 1000 V ranges, both input impedance settings achieve low charge injection.
The input impedance setting is only available when coupling is set to DC.
Example
dmm.digitize.func = dmm.FUNC_DIGITIZE_VOLTAGE
dmm.digitize.inputimpedance =
dmm.IMPEDANCE_AUTO
Set input impedance to be set automatically
when the digitize voltage function is
selected.
Also see
(on page 8-87)