Specifications

1.
Measure the voltage across the lower leg 1kΩ internal half bridge
resistor.
MEASure:VOLT:DC? (@110)
2. Measure the bridge output voltage (Vout) on channel 0. This is a DC
voltage measurement.
MEASure:VOLT:DC? (@100)
3. Measure the voltage on the leadwires (V_leadwire) for the strain
gage on channel 0 or 1.
MEASure:VOLT:DC? (@108) (channel 0)
MEASure:VOLT:DC? (@109) (channel 1)
4. Compute the value of leadwire resistance by substituting the voltages
and bridge completion resistance (120Ω or 350Ω) into the equation.
The following example determines the leadwire resistance on channel 0.
The program assumes the strain gage multiplexer uses the HP E1326B/
E1411B Multimeter as part of a scanning multimeter instrument. The
computer syntax used is HP BASIC running on a Hewlett-Packard Series
300 computer.
!Clear and reset the multimeter.
CLEAR 70903
OUTPUT 70903;"*RST"
!Measure the voltage across the lower leg of the internal
1
⁄
2
bridge resistor
!(V_lower).
OUTPUT 70903;"MEAS:VOLT:DC? (@110)"
ENTER 70903;V_lower
!Measure the bridge output voltage (Vout) on channel 0.
OUTPUT 70903;"MEAS:VOLT:DC? (@100)"
ENTER 70903;Vout
!Measure the voltage on the leadwires (V_leadwire).
OUTPUT 70903;"MEAS:VOLT:DC? (@108)"
ENTER 70903;V_leadwire
!Compute the value of leadwire resistance (350 ohm gage assumed).
R_leadwire=(V_leadwire*350)/(V_lower+Vout-V_leadwire)
PRINT “Leadwire resistance = ”;R_leadwire
END
A typical output from this program is:
Leadwire resistance = .411719144
110 Strain Gage Diagnostics Appendix C
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