Figure; Delta Measurement Using Bipolar Source; Figure 5-2 Delta Measurement Using Bipolar Source - Keithley 2182 User Manual

5-8 Ratio and Delta
To use the DC current-reversal technique, replace the constant current source with a bipolar
current source as shown in
–1mA. When using Delta, the Model 2182 performs the first voltage measurement (V1t1) while
sourcing +1mA. The second voltage measurement (V1t2) is performed while sourcing –1mA:
NOTE
V1t1
Delta is then calculated as follows:
Delta
Using Delta with a bipolar source effectively canceled the 10µV thermal EMF.
External triggering is required to control the timing between voltage measurements and
current source reversals. Trigger synchronization between the source and the Model 2182 is
explained in
measurement procedure using a

Figure 5-2

Delta measurement using bipolar source

SourceMeter
Source ±1mA
Figure
When using the Model 2182 to perform Delta measurements, RATE must be set to
1 PLC or 5 PLC to optimize measurement performance. At 1 PLC or 5 PLC, Delta
measurements will cancel thermal EMFs to a <50nV level.
= V + V V1t2= V
THERM DUT
= 10µV + 100µV = 10µV – 100µV
= 110µV= –90µV
V1t1 V1t2 – 110µV
= ------------------------------- - = --------------------------------------------- -
2
"Model 2182 and SourceMeter trigger
SourceMeter."
HI
2182
V
Delta
(CH 1)
LO
At +1mA:
V1t1 = 10µV + 100µV
= 110µV
V1t1 – V1t2 110µV – (–90µV)
V = =
DELTA
2
V = V
DELTA DUT
5-2. The current source will alternate between +1mA and
– V
THERM DUT
– – ( 90µV ) 200µV
= ---------------- - =
2 2
synchronization" which follows the
V
THERM
10µV
+
DUT
V = 100µV
DUT
0.1Ω
–
At –1mA:
V1t2 = 10µV – 100µV
= –90µV
= 100µV
2
100µV
"Delta