User guide

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.