Shunt Resistor
Fig. 5 Internal Shunt Location
The internal 59k Ohm shunt resistor is located
inside the 5M78 housing. To replace this resistor,
remove the spring and DIN Clip located on
rear of the case. Use a flat head screw driver to
separate the top and bottom of the case, typically
starting at the front connector positions. The
resistor is soldered to two terminal post as
shown in the diagram. Unsolder and resolder
the replacment shunt resistor or "short" for sensors
with internal shunt resistors. Reassemble the housing
and DIN clip. Ensure rear grounding clip and front
Master 5M78 Module
(Switch 6 to Master)
Additional 5M78 Module
Additional 5M78 Module
(Switch 6 to Slave)
(Switch 6 to Slave)
Fig. 7 Master / Slave Wiring
Master / Slave Connections
When more than one 5M78 is being used in the
same measurment setup, beat frequencies can be
produced by the excitation clock oscillator. To
prevent this, the user should declare one of the
5M78 units as a Master via switch 6 on the front
panel. The other units should be switched to Slave
and wired as shown with the SYC terminals
connected and a separate Power Common wire.
If the units share a common power supply, the
P com terminal should be connected at the modules.
Shunt Reference
Fig. 6 Internal Shunt Reference Solder Connections
The 5M78 internal shunt resistor is referenced
from + Signal to Sense for Shunt positive (SHP)
or - Sense for Shunt negative (SHN) when
activated via the terminals per Fig. 3. Provisions have
been incorporated to reference Common instead of
+ Signal for sensors that require this feature. To
accomplsih this, unsolder the "S" connection and
make a solder bridge across "C" to the middle pad as
shown in adjacent layout. Reassemble the
housing and DIN clip. Ensure rear grounding clip
and front cover are in place.
cover are in place.
