8808A 120V Fluke Electronics, 8808A 120V Datasheet - Page 98

• Manufacturer Part Number: 8808A 120V
• Description: DMM 5.5 RES RS-232 INTERFACE
• Manufacturer: Fluke Electronics
• Type: Digital (DMM)r

Specifications of 8808A 120V

• Includes: Test Leads
• Style: Bench
• Display Digits: 5.5
• Display Type: VFD, Dual
• Display Count: 200000
• Function: Voltage, Current, Resistance, Frequency
• Functions, Extra: Continuity, dB, Diode Test
• Features: Hold, Min/Max, RS-232 Port
• Ranging: Auto/Manual
• Response: True RMS
• Lead Free Status / RoHS Status: Not applicable / RoHS non-compliant
• Other names: 614-1068

A-8
8808A
Users Manual
Making Low-Level Current Measurements
There are many applications where obtaining the utmost accuracy in low-level current
measurements is critical. For example, determining the leakage current of a battery
operated device in its standby mode is critical in determining the time before battery re-
charge is needed. Traditional multimeters make these measurements using a shunt
method shown in Figure A-3. The shunt resistor converts the current to be measured to a
voltage, which is called the burden voltage. Since the internal impedance of the current
source is in parallel with the shunt resistor, the current flowing in the shunt resistor is less
than the actual value, thus causing an error.
Another method of low-current measurement is the feedback resistor method shown in
Figure A-4. The feedback resistor converts the current to be measured into a voltage. The
high gain operational amplifier forces the burden voltage to be rather low and thus
induces an error. The zero burden voltage measurement method used in the Meter gives a
more accurate measurement of low-level (leakage) currents.
I
IN
Figure A-4. Zero Burden Voltage Low-Level Current Measurement
Figure A-3. Shunt Method of Low-Level Current Measurement
I
IN
R
Internal
R
Internal
R
SHUNT
R
A
Feedback
A
V
V
OUT
OUT
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