Measuring Current, Ac/Dc; Current Measurement Error Calculations - Fluke 27/FM Operator's Manual

I DC VOLTAGE MEASUREMENTS
Loading Error in 0 /0 - 100 x Rs+ (Rs + IC)
Where: As Source resistance in ohms of circuit
being measured.
2 AC VOLTAGE MEASUREMENTS
First, determine input impedance, as follows.
10 7
v/7
1 7
72-
x- F. R M.0) 2
Where Zin = effective input impedance
Rin 10Iohms
Cm • 100 x 10 -12 Farads
F = frequency in Hz
Then, determine source loading error as follows:
(vector algebra required)
100 x Zs
Loading Error in % -
Rs - Zin
Where: Zs = source impedance
Zin -- input impedance (calculated)
Rs = source resistance
Z
in
Measuring Current
Figure 4. Voltage Measurement Error Calculations
When measuring voltages above 320V in Touch-Hold mode, use manual ranging to
minimize readings of stray voltages.
Measuring Current, AC/DC
WARNING
INSTRUMENT DAMAGE AND OPERATOR INJURY MAY RESULT
IF THE FUSE BLOWS WHILE CURRENT IS BEING MEASURED
IN A CIRCUIT WHICH EXHIBITS AN OPEN CIRCUIT VOLTAGE
GREATER THAN 600V. DO NOT ATTEMPT AN IN-CIRCUIT
CURRENT MEASUREMENT WHERE THE POTENTIAL IS GREATER
THAN 600V.
The multimeter features five ac current ranges and five dc current ranges.
All current ranges are fuse protected. If a fuse opens, refer to the fuse
replacement procedures in the "MAINTENANCE" section of this manual.
Current Measurement Error Calculations
In an ac or de current measurement, the voltage developed across the meter's
terminals is called burden voltage. The burden voltage for a full-scale
input is given for each range in Table 3 (specifications). The burden
voltage can affect the accuracy of a current measurement if the current
source is unregulated and the terminal resistance represents a significant
portion (1/1000 or more) of the source resistance. If burden voltage does
present a problem, the percentage of error can be calculated using the
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