Load Error (Ac Voltage) - UNI-T UT8805E Manual

Error (sine wave): sine wave error
Error (crest factor): outer error of crest factor
Error (bandwidth): the bandwidth error can be estimated according to this formula:
Bandwidth Error =
C.F. The Crest Factor
F Pulse fundamental frequency
BW Effective Bandwidth
Example:
Calculate the approximate measuring error of pulse train input, the crest factor is 2, and the fundamental
frequency is 20kHz. Suppose the one-year accuracy of the multimeter is: ± (0.05% of reading + 0.03% of
range).
Error sum = (0.05% of reading + 0.03% of range) + (0.05% of range) + (0.8% of reading) = 0.85% of
reading + 0.08% of range
4.3

Load Error (AC Voltage)

In AC voltage measurement, the input impedance of UT8805E is 1MΩ, and resistor is in parallel to 100PF
capacitors. The multimeter test lead also will introduce some capacitance and load. Table 4-2 shows the
approximate input resistance of the multimeter at various frequencies.
Table 4-2 Resistance at various frequencies
Input frequency
100Hz
1kHz
10kHz
100kHz
In low frequency measurement:
Load error (%) =
Additional error in high frequency measurement:
Load error (%) =
F Input frequency
Rs Internal resistance of signal
Cm Input capacitance (100pF) + capacitance of test leads
Input impedance
1MΩ
850kΩ
160kΩ
16kΩ
(% reading)
50
UT8805E Benchtop Digital Multimeter