Two-Wire
Measurements
Two-wire measurements are useful in applications where test lead
resistance is not critical. Because the multimeter measures the total
resistance between its terminals, lead resistance that is large relative to the
unknown resistance will cause inaccurate measurements. Thus, for all
resistance measurements and especially those on the lower ranges, the leads
should be as short as possible.
Two-wire measurements are specified as:
RESistance
This function appears in the
MEASure
and
CONFigure
commands as:
MEAS:RES? ...(@channel_list)
CONF:RES ...(@channel_list)
Four-Wire
Measurements
For applications which require accurate resistance measurements or where
long test leads are used, the 4-wire configuration should be used. In the
4-wire configuration, errors due to test lead resistance are eliminated since
only the voltage induced across the unknown resistance is measured.
Four-wire measurements are specified as:
FRESistance
This function appears in the
MEASure
and
CONFigure
commands as:
MEAS:FRES?...[(@channel_list)]
CONF:FRES ...[(@channel_list)]
Channel Pairs
Four-wire measurements with multiplexers use channel pairs. Channel pairs
on the HP E1345A 16-channel multiplexer, for example, are channels 00 and
08, 01 and 09, 02 and 10, ... 07 and 15. The lower channel in the channel pair
(00, 01, 02) is the sense channel. The higher channel (08, 09, 10) is the source
channel. When specifying a channel list, the lower "sense" channels are
specified.
Temperature
Measurements
The multimeter can make temperature measurements using specific
thermistors, thermocouples, and RTDs.
Thermistor
Measurements
The thermistor types supported are 2252
Ω
, 5000
Ω
, and 10000
Ω
. Use
thermistors that match the Omega 440xx series temperature response
curves. Thermistor measurements can be made in either a 2-wire or 4-wire
configuration. Two-wire measurements require the scanning multimeter.
Two-wire thermistor measurements are specified as:
TEMP THERmistor,
type
88 Understanding the HP E1326B/E1411B Multimeter
Chapter 4
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