Cleveland Motion Controls Classic Series DIN Rail Amplifier with Isolated Output MWI-13467 REV CA - Manual (Page 18)

C LASSIC S ERIES A MPLIFIER W / I SOLATED O UTPUTS MAN-13467 REV CA
Page 18 of 30
2.12.2.2 A PPLICATION I NTERFACE DETAILS
The 4-20 mA output stage is designed to drive a loop current through a floating burden resistance. Examples of
driving a loop current through a floating burden resistance include: a loop powered 4-20 mA display or, the isolated
input of receiving electronics (isolated Analog to Digital input). The 4-20 mA output can also drive non-isolated (or
ground referred) burden resistances provided that the circuit that employs the burden does not connect to the isolated
common (COM, J2-3) of the amplifier.
For a better understanding as to why the burden must be floating with respect to the amplifier’s isolated common
(COM, J2-3) refer to Figure 9. This figure illustrates that the 4-20 mA OUT (J2-7) is connected to the +15V internal
supply voltage and the 4-20mA RET terminal sinks loop current toward the -15V internal supply. A truly floating
burden receives the loop current that is controlled by the amount of current sinking into the -15V supply. The
current is supplied by the +15V supply. Incorrectly connecting burden resistance between the 4 -20mA OUT and
COM (J2-3) would cause excessive current to flow. Incorrectly connecting the 4-20mA RET (J2-8) to COM (J2-3)
results in the 4-20mA current being drawn from ground and bypassing the burden resistance.
Figure 9 - 4-20 mA Output Circuit Wired for Floating Burden