4-8
IM CA150E
4.4 Source Resistance (Ω) Signals
Procedure for Generating Resistance Signals
• The instrument generates a resistance signal by receiving the
resistance-measuring current I supplied from the device under calibration
(resistance meter, RTD thermometer, etc.) and delivering
the voltage V = R × I proportional to the preset resistance R between
the output terminals, and thus producing the equivalent resistance R = V/I.
Consequently, the instrument generates the signal correctly only for
such devices that employ this method of measurement.
• The allowable range of the resistance measuring current I that
the instrument receives from a resistance measuring device under
calibration is rated as 0.01 to 5 mA.
(This varies depending on the generated resistance value. For details,
refer to the specifications.)
Obtaining Accurate Measurements
• Since the generated resistance value is calibrated without including
the voltage drop component of the lead cables, the resistance
(approximately 0.1 Ω on a round-trip basis) of the lead cables becomes
an error in the case of a load current.
• For accurate generation of resistance signals, use a three-wire connection
for output. (Refer to the figure below.)
• If the capacitance between the terminals of a device under calibration is
greater than 0.01 µF, the instrument may be unable to generate correct
resistance values.
Three-wire Connection Output Method
Attach another black source lead cable (98020) to the output terminal L side.
Red
Black
CA150
H L
SOURCE
H
L
L'
Device under calibration
(Three-wire measuring equipment)
4.4 Source Resistance (Ω) Signals
