Introduction; Overview; Electronics Module; Figure 1-1 Directline® Sensor - Honeywell DirectLine DL421 User Manual

1.1 Overview

The DirectLine® Sensor consists of an electronics module connected to a
Durafet® II, Durafet® III, Meredian® II or HPW7000 pH electrode that eliminates
the need for pre-amps, transmitters, and analyzers in pH applications.
The modular electronics design can be separated from the sensor, allowing the
sensor to be easily removed or replaced while retaining power to the electronics
module.
The DL421 electronics module is contained in a Nema Type 4x polysulfone
housing. The Module can be mounted as an integral unit directly connected to the
electrode or remotely using an electrode with a cable. The sealed plastic housing
has plug-in connections for the pH electrode and 4-20 mA cordset.

1.2 Electronics Module

The electronics module is loop-powered by 16-42 Vdc and will modulate its supply
current from 4 mA to 20 mA, depending upon the pH value that is sensed by the
electrode. The transmitted loop current is compensated for temperature internally
using the standard Honeywell 8550 thermistor.
For submersion or special wiring applications, the remote electronics module is
compatible with the existing Durafet II, Meredian II or HPW7000 technology without
modification. A Durafet II or Meredian II cable length is supported with direct
connection to the electronics module.
A 4-20 mA output connection is provided via a 6m cordset or a customer supplied
cable used in combination with a field wiring connector.
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1. Introduction

Figure 1-1 DirectLine® Sensor
DirectLine® DL421 Sensor Module User Manual
Introduction
1