Rosemount 3150 Series
Reference Manual
00809-0100-4835 Rev BE
February 2018
49
Operation
CURRENT CONTROL
The current control amplifier consists of two operational
amplifiers, two transistors, and associated components. The
first amplifier provides an adjustable gain output proportional
to the sum of the differential sensor current and a zero
adjustment current. This output is supplied to the second
amplifier, which controls the current in the 4-20 mA loop
proportionally.
CURRENT LIMIT
The current limiter prevents output current from exceeding 30
mA nominal in an overpressure condition. Conversely,
minimum output is limited to 3 mA nominal. Both the minimum
and maximum current limits may vary slightly depending upon
sensor pressure range code and associated calibration.
REVERSE POLARITY
PROTECTION
A diode provides reverse polarity protection.