Tru Ohms Ratio - Fluke 8508A User Manual

8508A
Users Manual
To avoid equipment damage when using the HiV function make sure
that circuits or components connected to the Multimeter can withstand
at least 240 V dc.
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 the 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.
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.
3-30
HIGH VOLTAGE
INPUT HI
SENSE HI
Front Input
SENSE LO
INPUT LO
INPUT HI
SENSE HI
Rear Input
SENSE LO
INPUT LO
Figure 3-12. Tru
XW
Caution
Note
Potential
Difference
Measurement
Ratio Measurements
Stimulus Current
Source (Reversing)
adj132f.eps