RS PRO RSDM-9060, User Manual

Page: 87 / 412

87
The error of current shunt
Background
The principle of current measuring is to obtain
current via the voltage proportionated by the
measured shunt resistor and the current under
test. The circuit is basically designed by high
impedance (0.01Ω~100Ω approximately) and with
shortcoming of voltage drop by shunt. There will
be obvious error occurred while measuring low
current due to the measurable voltage generated
by a larger shunt.
An ideal ammeter never changes flowing route of
current, and thus it owns the characteristics of both
zero-input resistor and zero-input voltage drop. In
practice, however, ammeter always generates an
input voltage drop while measuring, which is
known as burden voltage in series.
Diagram
Fuse
Rshunt
Rline
3A
Rline
HI
LO
DMM INPUT