Xylem H-3521 - Manual (Page 9)

Chapter 1
Introduction
H-3521
Introduction 1-1
1.0 Introduction
The W ATER LOG ® H-3521 is a digital pressure transducer specifically designed for water level
monitoring. The H-3521 directly measures water or other fluid pressure over a broad
temperature range. Typical applications include monitoring snow pillows to measure snow pack,
measurement of water in accumulating rain gauges, and fluid pressure in weirs and dams. The
H-3521 can be used in a gas-purge bubbler installation however, Design Analysis Associates,
Inc., manufactures other instruments specifically for that application.
The H-3521 has RS-232, SDI-12 and Modbus “smart” digital interfaces together with a 4-20mA
analog output. The sensor makes multiple pressure measurements, averages the results and
converts the measurement data into units of PSI, Feet, Meters or other engineering units.
The H-3521 is easy to use and works with any SDI-12 data recorder. The “Serial-Digital
Interface” is ideal for data logging applications with the following requirements.
! Battery powered operation with minimal current drain
! Pressure measurement data is transmitted digitally over long cable lengths without error
! Multiple sensors on a simple three-wire cable
! Up to 250 feet of cable between a sensor and the data recorder
(Use of H-423, SDI-12 to RS485 converter extends the range to 1000's of feet)
(H-4500 fiberoptic media converter works up to 1.2 miles)
The H-3521 has the following features:
! Simple to install, use, and maintain (no on-site calibration required)
! Performs extremely accurate measurements.
! Linear deviation is less than 0.05%
! Resolution is 1 part in 1,000,000
! Accuracy over temperature range exceeds ±0.02 ft. of water
! Enclosure is nonconductive and corrosion proof
! Stainless steel sensor diaphragm
! Sensor has an atmospheric vent for compensation of barometric pressure changes
! Low current operation (less than 1 milliamp typical standby)
! Simple RS-232 menu interface for quick and easy setup.(No external module required)
! Outputs a 4-20mA signal.(no external module required)
! Extended SDI-12 commands for setting the Stage to the current water elevation.