Panametrics DewPro MMY30, Руководство пользователя, Страница: 12 / 43

Chapter 1. General System Information
4 DewPro
®
MMY30 User’s Manual
1.4 Theory of Operation
1.4.1 4 to 20 mA Loop
The DewPro MMY30 transmitter is powered by a DC voltage supply from 12 to 28 VDC. At the nominal 24 VDC supply,
the maximum loop resistance is 600 ohms. 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
with a standard range 0-100 ppm
v
.
1.4.2 Bypass
In dryer applications, the moisture sensor performs best when mounted in a bypass. The built-in bypass of the
DewPro MMY30 eliminates costly hardware associated with traditional sampling methods. The DewPro MMY30
installs simply into the process with its G½ or ½” MNPT threaded connection.
1.4.3 Planar Sensor
The heart of the DewPro MMY30 transmitter is the planar aluminum oxide sensor that provides longer calibration
stability, excellent corrosion resistance, and improved speed of response. The sensor is mounted on a ceramic
substrate, giving a reduced temperature coefficient.
1.4.4 Calibration
Each DewPro MMY30 is factory calibrated against precise NIST certified moisture references and has an accuracy of
±2°C dewpoint at 25°C temperature.