JF-1A Conductivity Sensor
A440-009
Page 39 of 56
FEBRUARY 2009
November 22, 2010
JF-1A FUEL CONDUCTIVITY SENSOR
Technical Application Note 10-006
Power/Ground Requirements for JF-1A, when 4-20
mA and Serial Data Ports are used simultaneously
Background
In some applications of the JF-1A both the current ports and serial data ports
are used. In these applications the user must take care to ensure that input
voltage ratings are not exceeded and that power supplies do not create multiple
ground paths through the instrument. These issues can either result in
improper readings from the sensor, or result in damage to the sensor output
electronics.
JF-1A has 3 Distinct Outputs
Conductivity
: is output as a 4-20 mA signal. This 2-Wire port is also
used to supply power to the instrument when used alone. The
current that flows in the loop is proportional to the conductivity read
by the meter.
Temperature:
is output as a 4-20 mA signal. This 2-Wire port does
not power the instrument, so it cannot be used alone. The current
that flows in the loop is proportional to the temperature read by the
meter. (The loop needs its own external power supply).
Serial data
: This 4-Wire port allows the connection of a RS-232
equipped computer to access both the conductivity and temperature
data from the instruments serial port. As this is a four wire port.
Power to run the instrument can also be applied via this port to
operate the instrument. The power input is OR’ed with the
conductivity current output port listed above.
General Power Requirements
