Fluke 8508A - Tru Ohms Ratio

3
Making Measurements
Multimeter Inputs
Caution
HIGH VOLTAGE
To avoid equipment damage when using the HiVΩ function make sure
that circuits or components connected to the Multimeter can withstand
at least 240 V dc.
Note
Scan of Temperature Measurement - Scan Mode is not available in the PRT
Function. Temperature Measurements from two PRTs (each with its own
linearization coefficients) connected to the Front and Rear Terminals may
however be compared under remote control of the DMM.
Tru Ohms Ratio
When the Tru Ohms Scan Mode of operation is selected a stimulus current (of alternating
polarity) is applied through both resistors simultaneously, and the potential difference
measured across the resistors is scanned between the Front and Rear Terminals, as shown
in figure 3-12. This measurement technique can be beneficial for lower value resistance
measurements between an unknown and a reference resistor, and reduces self heating
(power) modulation that would otherwise result from scanning the stimulus current
between the two resistors under test.
Front Input
Rear Input
INPUT LO
SENSE LO
SENSE HI
INPUT HI
INPUT LO
SENSE LO
SENSE HI
INPUT HI
Potential
Difference
Measurement
Stimulus Current
Source (Reversing)
adj132f.eps
Figure 3-12. TruΩ Ratio Measurements
The sequence of measurement is:
1. Set Forward Current, Measure potential difference at Rear.
2. Set Reverse Current, Measure potential difference at Rear.
3. Set Forward Current, Measure potential difference at Front.
4. Set Reverse Current, Measure potential difference at Front.
Autorange is not available in this mode.
3-31