5560A/5550A/5540A
Operators Manual
30
Four-Wire versus Two-Wire Connections
Four-wire and two-wire connections refer to methods used to connect the Calibrator to the DUT to
cancel out test lead resistance to assure the highest precision of the calibration output. The external
sensing capability of the four- and two-wire compensated connections provides increased precision for
lower impedance values. Part of setting up the Calibrator output for resistance, capacitance,
inductance, and RTD includes selections for four-wire compensation (
Comp 4 Wire
), two-wire
compensation (
Comp 2 wire
) and two-wire no compensation (
Comp OFF
). (See
Set Inductance Output (Not Available on 5540A)
, and
Temperature Simulation (RTD) Source
.
Note that compensated connections for capacitance and
inductance are to compensate for lead and internal resistances, not for lead and internal capacitances
or inductances. See
for impedance values where compensation is available.
Four-Wire Connection
The four-wire connection is typical for calibrating laboratory measurement equipment. Increased
precision is provided by four-wire connections. See
for impedance values where
compensation is available.
Two-Wire Compensation
The two-wire connection is typical for calibrating precision handheld Digital Multimeters (DMMs) with a
two-wire input. Increased precision is provided for lower impedance values. For higher values, the
Calibrator changes the compensation to off (
Comp OFF
for impedance values
where compensation is available.
Compensation Off
Compensation off is a typical connection used to calibrate handheld analog meters or DMMs with a
two-wire input. This connection is available for most values of resistance, capacitance, and inductance
and is usually selected when the analog meter or DMM level of accuracy does not require the
additional precision. This is the default condition whenever an impedance output is made, following an
output that was not impedance.
Cable Connections
Table
indicates a figure reference for each type of connection between a DUT and the Calibrator,
referencing Figures
through
.
When calibrating Resistance Temperature Detector (RTD) meters with the three-terminal connection
shown in Figure
, be sure the test leads have identical resistances to cancel any errors due to lead
resistance. This can be accomplished, for example, by using three identical test lead lengths and sizes
and identical connector styles.
When you calibrate a thermocouple meter, it is important to use the correct hookup wire and a
connector between the Calibrator front-panel TC terminal and the DUT. You must use thermocouple
wire and connectors that match the type of thermocouple. For example, if you simulate a temperature
output for a type K thermocouple, use type K-thermocouple wire and type-K plugs for the hookup.
