GE DewPro MMY30 - Theory of Operation

November 2005
1-4 General System Information
Theory of Operation
4 to 20 mA Loop The DewPro MMY30 microprocessor controlled electronics operate
with a DC voltage supply from 12 to 28 VDC. At the nominal 24 V
DC supply, the maximum loop resistance is 600 Ohm. The signal is
represented by the 4 to 20 mA loop current and is directly
proportional to the dewpoint range in °C or °F. In the standard range,
4 mA corresponds to -90°C (-130°F) and 20 mA to +10°C (+50°F)
dewpoint temperature.The optional unit of measure is ppm
v
in the
standard range 0-100 ppm
v
.
Bypass In dryer applications, the moisture sensor performs best when
mounted in a bypass. The built-in bypass of the DewPro eliminates
costly hardware associated with traditional sampling methods. The
DewPro installs simply into the process with its G ½ or ½” MNPT
threaded connection.
Planar Sensor The heart of the MMY30 is the planar sensor element. It incorporates
a superior aluminum oxide sensor that provides longer calibration
stability, excellent corrosion resistance, and improved speed of
response. The sensor, mounted on a ceramic substrate, also has a
reduced temperature coefficient.
Calibration Each DewPro is factory calibrated against precise NIST certified
moisture references and has an accuracy of ±2°C dewpoint at 25°C
temperature. For field validation, GE Sensing offers a unique
validation device. The MMY245 field validator connects to the
DewPro on site and offers a one-point or two-point correction.