Georg Fischer 2764-2767 Operating Manual

Signet 2764-2767 Differential DryLoc® pH/ORP Electrodes

4

Features

• Differential design
for stable measure­ments in the most
aggressive applica­tions

• Long service life even
in severe or difficult
chemical applications

Description

The Signet 2764-2767 Differential pH & ORP
electrodes are built with the DryLoc

®

a Ryton

body, and PTFE reference junction to
handle even the most extreme and harshest of
chemical applications.

These differential electrodes use the field­proven 3-electrode differential technique: the pH
and reference electrodes are measured against
a ground electrode, insuring a steady and stable
signal. The key feature of the differential design
is the reference electrode. The reference ele­ment is housed in a glass half-cell embedded
in the reference chamber and is protected from
compounds that may contain sulfides (H
metals, including lead, mercury, and silver. To
ensure a long service life, the reference features
a refillable electrolyte chamber and a replace­able equitransferant salt bridge, both easily
serviced in the field. The patented porous PTFE
reference junction resists fouling, clogging and
chemical attack.

®

connector,

S) and

2

System Overview

In-Line Installation

Panel Mount

Signet Instrument
(sold separately)

5700 8750 8900

Signet 2750 or
Signet 2760
(sold separately)

Signet 2764-2767
Differential pH/ORP Electrodes

4 to 20 mA Input

Chart Recorder

Signet 2750
(sold separately)

OR

Programable

Controller

PLC

Pipe, Tank or Wall Mount

Signet Instrument
(sold separately)

Logic

Signet
Universal
Adapter Kit
(3-8050)
(sold separately)

Signet 2760
(sold separately)

8750

The other elements of the design are the
solution ground, the pH/ORP electrodes,
and the temperature element. The solution
ground eliminates noisy measurements by
draining electrical current away from the
reference electrode. The pH/ORP electrodes
are designed with a flat or bulb measure­ment surface, and a temperature device that
is positioned at the tip of the measurement
surface, making the temperature response of
T

less than 1 minute. Various temperature

95%

devices offered include 3KΩ, 300Ω, or PT-1000
RTD. The electrodes are used with the Signet
2750 Sensor Electronics, which provides a
blind 4 to 20 mA output or using the digital

3

(S

L) output may be used to connect to the
Signet 8900 instrument. The electrodes can
also be used with the Model 2760 preamplifier
to connect to the Signet 5700, 8750, or other
suppliers’ instruments.

Submersible Installation

Other Instruments

Customer supplied

Flow

Signet 2760
(sold separately)

Panel, Pipe, Tank, Wall Mount

678

RELAY 2

10

RELAY 1

pH

12

2

14

0

ENTER

+GF+

SIGNET

Signet or Other Instrument

5700 8750 8900

Pipe extension
or conduit with
3/4 in. FNPT
threads
(customer supplied)

Signet 2750 or
Signet 2760
(sold separately)

Signet 2764-2767
Differential
pH/ORP Electrodes

• Water-tight DryLoc

®

connector with foul­proof gold contacts

• Porous PTFE refer­ence junction

• Rebuildable refer­ence electrode

• Solution ground

• Temperature sensor
(pH)

• Easy sensor replace­ment using DryLoc®
electrode connector

• Quick temperature
response

• Compatible with all
Signet instruments
and other suppliers’
pH/ORP instruments

Applications

• Water and Waste
Water Treatment

• Coagulation and
Flocculation

• Plant Effluent

• Plating Baths

• Scrubbers

• Textile Dye Process

• Harsh Chemical

Applications

• Heavy metal Removal
and Recovery

• Toxics Destruction

• Surface Finishing

Fittings - Customer supplied

96

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Electrode Key Feaures and Benefits:

• Glass encased reference elec­trode protects the Ag/AgCl (sil­ver/silver chloride) element from
reacting with certain chemical
compounds that typically leach
into the reference chambers.
Keeps the pH/ORP reading
stable.

• Large volume reference elec­trolyte chamber resists dilution
over time for a long service life.
Chamber is refillable.

• Salt Bridge serves as a double
reference junction and is the
first line of defense to keep out
process chemicals from the
reference electrolyte chamber. It
is built with a porous PTFE refer­ence junction which is highly
compatible to chemicals , resists
fouling and build-up of dirt.

• Ryton® body for chemical com­patibility to most harsh chemi­cals. Also able to withstand high
temperatures.

• DryLoc® connector with corro­sion resistant gold pins for quick
and easy sensor removal.

• Capillary TC (temperature sen­sor) embedded in tip of pH/ORP
electrode for quicker tempera­ture response than most other
electrodes on the market.

Electrode Cut-away View

Removable/replaceable
reference salt bridge

Solution ground

Glass enclosed
reference silver
chloride element

Reference Chamber
with electrolyte

Temperature
Element

pH/ORP
electrode

Choosing

Products

Instrument

Multi-Pa-

rameter

Flow

pH/ORP

Conductivity/

Resistivity

Pressure, Level

Temperature,

Model 2764-2767 Electrode Compatibility to Sensors, Preamplifiers, and Instruments

Compatible Signet Instruments

Sensor Temp.

2764-1 3 Kohm 2760-1, -2,

2764-2 PT 1000

2764-3 300 ohm - - - - 2760-1, -2, -11, or -21
2765-1 10 Kohm 2760-1, -2,

2765-2 PT 1000 - - - - 2760-1, -2, -11, or -21
2765-3 300 ohm - - - - 2760-1, -2, -11, or -21
2766-1 3 Kohm 2760-1, -2,

2766-2 PT 1000

Compatible Electrodes

2766-3 300 ohm - - - - 2760-1, -2, -11, or -21
2767-1 10 Kohm 2760-1, -2,

2767-2 PT 1000 - - - - 2760-1, -2, -11, or -21
2767-3 300 ohm - - - - 2760-1, -2, -11, or -21

*Must have internal preamplifier in instrument
**Must use sensor with compatible temperature element; contact technical service for questions

Element**

5700 8750 8900 PLC Other Mfr’s Instruments

-11, or -21

-11, or -21

-11, or -21

-11, or -21

2760-1, -2,

-11, or -21

--

2760-1, -2,

-11, or -21

2760-1, -2,

-11, or -21

--

2760-1, -2,

-11, or -21

--

any 2750 w/
digital output

any 2750 w/
digital output

--

any 2750 w/
digital output

any 2750 w/
digital output

any 2750 w/4 to
20 mA output

any 2750 w/4 to
20 mA output

any 2750 w/4 to
20 mA output

any 2750 w/4 to
20 mA output

with internal preamplifiers*

Differential sensors
must use preamplifier
at sensor location;
otherwise, sensor signal
will be too erratic due to
high impedance signals

Other Mfr’s Instruments requiring
external preamplified signals**

2760-1, -2, -11, or -21

2760-1, -2, -11, or -21

2760-1, -2, -11, or -21

2760-1, -2, -11, or -21

2760-1, -2, -11, or -21

2760-1, -2, -11, or -21

Products

Other

Installation

Wiring &

Reference

Technical

Temperature/

Pressure

Graphs

of Terms

Glossary

Reference

Part No.

www.gfsignet.com

Index

97

General

Compatibility: Signet 2750 and 2760
Operating Range:

• 2764/2766: 0 to 14 pH

• 2765/2767: +/-1500 mV (ORP)
Pipe Size Range: 1 inch and up.

Mounting:

• In-line/vertical mounting: Use sen­sor 1 inch threads. Sensor must be
mounted at least 5 degrees above the
horizontal axis.

• Submersible mounting: Use threads
on Model 2750 or 2760; requires 3/4
inch NPT or ISO7-1/ 3/4 inch male
threaded extension.

Reference:
Electrolyte:

3.5 M KCl, solidified acrylamide gel

Element: Ag/AgCl
Temperature Sensor:

• pH: 3KΩ, PT1000 RTD, or 300Ω

• ORP: 10 KΩ, PT1000 RTD, or 300Ω

Temperature response time: τ

< 1 min.

95%

Primary Functions:

• 2764 and 2765:

Flat surface resists fouling

• 2766 and 2767:

Bulb surface for general use

Wetted Materials:

Body: Ryton

®

Reference junctions: PTFE
Sensing surface:

• Glass membrane: (pH)

• Platinum: (ORP)
O-rings: FPM
Solution ground: carbon graphite

Max. Temperature/Pressure rating:

Operating Temperature:
0°C to 195°C (32°F to 203°F)
Max. Operating Pressure:

6.89 bar (100 psi) @ 95°C (203°F)
Storage Temperature: > 0°C (15°F)

Shipping Weight: 0.25 kg (0.55 lbs.)

Standards & Approvals

• CE

• Manufactured under ISO 9001:2000
for Quality and ISO 14001:2004 for
Environmental Management

DimensionsSpecifications

38.6mm
(1.52 in.)

35.6mm
(1.4 in.)

32.5mm

(1.28 in.)

133.8mm
(5.27 in.)

1 in.
NPT

28.7mm
(1.13 in.)

25.4mm
(1.0 in.)

A differential electrode solves many common problems typically experienced by standard pH/ORP electrodes at
troublesome measuring points. See the table below to find the common problem, cause and effect, and the Differential
pH/ORP electrode solution.

Standard pH/ORP electrode problem: Cause and Effect The Differential Electrode Solves the Problem!

Reading slowly drifts over time and/or
responds slowly

Reading slowly drifts over time and/or
becomes erratic

Reading suddenly and unexpectedly
shifts

• Chemical attack from Hg++, Cu+, Pb++,
ClO4- or other compounds which dilute the
KCl reference electrolyte concentration.

• Reference junction gets clogged from
oils, grease, and dirt from the process.

• Chemical attack of the Ag+ reference bil­let from Br-, I-, CN-, and S- compounds.

• Clogged reference and slowed reading
from silver compounds forming on the
inside of the reference electrode from Ag+
of reference element reacting and precipi­tating AgS, AgBr, AgI, AgCN, or other silver
compounds.

• Stray electrical currents in the process
liquid; Ag+ reference element picks up cur­rent and shifts reference reading, resulting
in shifted pH reading. The Ag+ element will
eventually become totally stripped. Pro­cess must be properly grounded or place
metal rod close to electrode.

• Salt bridge will slow or stop attack. If attack­ing ions penetrate the salt bridge and affect the
KCl, simply refill KCl solution

• Readings do not drift due to stable differential
reference design, however may require cleaning
or replacement of the salt bridge if electrode
gets too dirty.

• Will not affect electrode due to Ag+ element
protected in glass encased reference electrode.

• Will not affect electrode due to Ag+ element
protected in glass encased reference electrode

• Will not affect electrode due to Ag+ element
protected in glass encasement; also, electrode
has a built in solution ground, so if there is a
stray current, it will not be seen by the electrode

Application Tips:

• Use the flat glass electrodes when a self-cleaning feature is desired; especially useful in applications with abrasive chemicals.

• Use bulb electrodes for general purpose applications

• ORP electrodes are generally used for chemical reaction monitoring, not control.

• Ensure that electrode materials are chemically compatible with the process liquid.

98

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Model 2764-2767
Ordering Notes:

1) pH and ORP electrodes
require connection to
model 2750 or 2760.

2) To replace electrodes,
simply twist from pre­amplifier to replace with
new electrode.

3) Conduit and mounting
brackets for submers­ible installations must
always be used (cus­tomer supplied)

4) Adapters from 1 -1.5 in.
are available.

5) Use sensor threads for
in-line mounting; Model
2750 or 2760 threads for
submersible mounting.

6) Reference electrode can
be rebuilt with replace­ment electrolyte and
salt bridge.

Ordering Information

Electrode Part Number- Choose either a pH or ORP Electrode

pH Electrode

3-2764 Flat pH surface differential electrode
3-2766 Bulb pH differential electrode with bulb protection

Temperature Element - Choose one

-1 3K Ω for pH for connection to 8750 or 5700 instruments when used with the 2760 preamplifier

-2 PT1000 RTD for pH for use with the 8900 instrument when used with the 2750 sensor electronics

-3 300 Ω for connection to other instruments when used with the 2760 preamplifier or connector

ORP Electrode

3-2765 Flat ORP surface differential electrode
3-2767 Bulb ORP differential electrode with bulb protection

Temperature Element - Choose one

-1 10 KΩ ID resistor for connection to 8750 or 5700 when used with the 2760 preamplifier or connection to
the 8900 with used with the 2750 sensor electronics

-2 PT1000 RTD for connection to other instruments using the 2760 preamplifier or connector

-3 300 Ω for connection to other instruments using the 2760 preamplifier or connector

3-2765 -1 Example Part Number

Preamplifiers & Sensor Electronics - Choose one (required for installation of any pH or ORP electrode)

The sensor electronics below can be used with the Signet 8900 or as a blind transmitter with 4 to 20 mA output for con­nection to PLC, PC, chart recorders, and other devices requiring 4 to 20 mA input.

3-2750-1 In-line Sensor electronics w/junction box (yellow body)
3-2750-2 In-line Sensor electronics w/junction box and EasyCal (yellow body)
3-2750-3 Submersible Sensor electronics w/4.6m (15 ft.) cable and 3/4 inch NPT conduit threads
3-2750-4 Submersible Sensor electronics w/4.6m (15 ft.) cable and ISO 7/1-R 3/4 conduit threads

The Preamplifiers below can be used with the Signet 5700 or 8750 Instruments
3-2760 pH/ORP Preamplifier (for use with the 8750 or 5700 instrument) or connector (for use with other manufac-

turers instruments) with 4.6m (15 ft.) cable
Preamplifier or Connector Style; Choose one

-1 Preamplifier with 3/4 inch NPT threads

-2 Preamplifier with 3/4 inch ISO threads

Mounting Configurations

- Submersible mounting (gray body)
1 In-line mounting (yellow body)

3-2760 -2 1 Example Part Number

Choosing

Products

Instrument

Multi-Pa-

rameter

Flow

pH/ORP

Conductivity/

Resistivity

Pressure, Level

Temperature,

Products

Other

Mfr. Part No. Code

3-2764-1 159 000 943
3-2764-2 159 000 944
3-2764-3 159 000 945
3-2765-1 159 000 946
3-2765-2 159 000 947
3-2765-3 159 000 948
3-2766-1 159 000 949
3-2766-2 159 000 950
3-2766-3 159 000 951
3-2767-1 159 000 952

Mfr. Part No. Code

3-2767-2 159 000 953
3-2767-3 159 000 954
3-2750-1 159 000 744
3-2750-2 159 000 745
3-2750-3 159 000 746
3-2750-4 159 000 842
3-2760-1 159 000 939
3-2760-2 159 000 940
3-2760-11 159 001 367
3-2760-21 159 001 368

Accessories and Replacement Parts

Mfr. Part No. Code Description

3864-0001 159 001 007 Replacement Salt Bridge
3864-0002 159 001 008 Replacement reference electrolyte solution,
500 mls
2120-0015 159 001 009 CPVC adapter: 1.5 in. MNPT to 1 in. FNPT
2122-0015 159 001 010 PVDF adapter: 1.5 in. MNPT to 1 in. FNPT
3-0700.390 198 864 403 pH Buffer kit
3-2759 159 000 762 pH/ORP System Tester
3-2759.391 159 000 764 Adapter Cable for use with 2750

Installation

Wiring &

Reference

Technical

Temperature/

Pressure

Graphs

of Terms

Glossary

Reference

Part No.

Index

www.gfsignet.com

99