Detcon DM-434B User Manual

Model DM-434B

detcon inc.

Oxygen Deficiency Sensor (0-25% O2)

Operator’s Installation & Instruction Manual

October 21, 2008 • Document #2021T • Version 1.7

CAUTION: FOR SAFETY REASONS THIS EQUIPMENT MUST BE OPERATED
AND SERVICED BY QUALIFIED PERSONNEL ONLY. READ AND UNDERSTAND
INSTRUCTION MANUAL COMPLETELY BEFORE OPERATING OR SERVICING.

ATTENTION: POUR DES RAISONS DE SECURITE, CET EQUIPEMENT DOIT ETRE
UTILISE ENTRETENU ET REPARE UNIQUEMENT PAR UN PERSONNEL QUALI­FIE. ETUDIER LE MANUEL D'INSTRUCTIONS EN ENTIER AVANT D'UTILISER,
D'ENTRETENIR OU DE REPARER L'EQUIPEMENT.

Table of Contents

1.0 Description

2.0 Principle of Operation

3.0 Application

4.0 Specifications

5.0 Installation

6.0 Start-up

7.0 Calibration

8.0 Spare Parts List

9.0 Warranty

10.0 Service Policy

Detcon Model DM-434B Oxygen Sensor PG.2

1.0 DESCRIPTION

Construction of Galvanic Cell

Cathode

Anode

Electrolyte

Solution

Diffusion Barrier

Air Supply

Load

Resistor

T

E

X

A

S

H

O

U

S

T

O

N

SIGNAL

DM-434B

ZERO

FINE

COARSE

+

0-25%

O

2

detcon inc.

detcon inc.

Detcon Model DM-434B, oxygen sensors are designed to detect and continuously monitor O2 in air over the
range of 0-25%. Method of detection is by diffusion/adsorption requiring no moving parts. The sensor
assembly consists of an galvanic air battery cell mounted in a stainless steel housing, a signal conditioning

ontrol transmitter circuit, a terminal board, an explosion proof junction box and a machine fitted rain shield.

c

1.1 Sensor Technology

The sensor technology is of the two electrode, galvanic metal air battery type cell, which is housed as a
field replaceable plug–in module. The cell is diffusion limited and functions as a direct current generator
proportional to the amount of oxygen adsorption. The sensors are temperature compensated and show
good accuracy and stability over the operating temperature range -4° to +122° Fahrenheit. The sensor is
warranted for one year and has an expected service life of up to two years in ambient air at 20.9% oxygen.

1.2 Control Transmitter Circuit

The 4-20 mA DC control transmitter is equipped with zero and span adjustments accessible through a face
plate allowing one man remote calibration without communication with control room personnel. The trans­mitter circuit module is plug-in replaceable, via gold plated pins, facilitating easy maintenance and repair.

Detcon Model DM-434B Oxygen Sensor PG.3

1.3 Terminal Board

BLU

WHT

MA

Sensor

To Controller

Te rm i na l s

+VDC

VDC Common

he terminal board is mounted in the explosion proof enclosure and includes: the mating connector for the

T
control circuit, reverse input and secondary transient suppression, input filter and terminals that do not
require lugs for all field wiring.

1.4 Explosion Proof Enclosure

The explosion proof enclosure has 3/4” NPT female entry ports. It’s constructed of cast metal and given an
epoxy finish. The enclosure is fitted with a threaded cover. Electrical classification is Class I; Groups B, C,
D; Div. 1.

1.5 Rain Shield

The machine fitted rain shield is designed to help prevent obstruction of the sintered stainless steel flame
arrestor as a result of liquid or solid contact. Material of construction is Dupont Delrin.

Detcon Model DM-434B Oxygen Sensor PG.4

2.0 PRINCIPLE OF OPERATION

FUNCTIONAL BLOCK DIAGRAM

PRE-AMP

SIGNAL

CONDITIONING

(ZERO/SPAN)

XMTR

P

OWER

SUPPLY

I/O CIRCUIT

PROTECTION

SIGNAL OUT

POWER IN

SENSOR

Method of detection is by a controlled rate of diffusion. Air and gas diffuse through a sintered stainless
steel filter and a diffusion barrier. As oxygen is adsorbed into the electrolyte solution a current is generat­ed between the cathode and anode electrodes. This current output rises with increases in oxygen concen-

ration and reverses with lower concentrations. The quick response of the cell results in continuous moni-

t
toring of ambient air conditions.

3.0 APPLICATION

Model DM-434B sensors are designed to detect and monitor oxygen deficiency in ambient air in the range of
0-25%. Operating temperature range is -4° F. to +122° F. While the sensor is capable of operating outside
these temperatures, performance specifications are verified within the limit.

3.1 Sensor Placement/Mounting

Sensor location should be reviewed by facility engineering and safety personnel. Area leak sources and
perimeter mounting are typically used to determine number and location of sensors. The sensors are gen­erally located 2 - 4 feet above grade.

3.2 Interference Data

Methane 100% = 0
Hydrocarbons 100% = 0
Hydrogen 100% = < -2%
Carbon Monoxide 20% = < -0.5%

4.0 SPECIFICATIONS

Method of Detection

Air battery diffusion/adsorption

Measurement Range

0-25% O2

Accuracy/Repeatability

± 2% FS
± 2% FS

Response /Clearing Time

T90 < 20 seconds; T90 < 20 seconds

Zero Drift

< 2% per month

Operating Temperature Range

-4° to +122° F; -20°C to +50°C

Operating Humidity Range

0-99% RH (non-condensing)

Detcon Model DM-434B Oxygen Sensor PG.5

Linearity

0.5% FS

±

Output

Linear 4-20 mA DC

Input Voltage

11.5-28 VDC

Power Consumption

< 0.6 watts

Electrical Classification

Class I; Groups B, C, D; Div. 1.

Safety Approvals

CSA/NRTL (US OSHA Certified)

Sensor Warranty

2 year conditional

Field Wiring

Maximum loop load 650 ohms at 24 VDC

5.0 INSTALLATION

Optimum performance of ambient air/gas sensor devices is directly relative to proper application and
installation practice.

5.1 Field Wiring Table

Detcon Model DM-434B sensors are two wire loop powered. Wiring designators are + (+ power) and MA
(– power). Maximum single conductor resistance between sensor and controller is 10 ohms. Maximum
wire size for termination in the sensor assembly terminal board is 14 gauge.

AWG Meters Feet

20 240 800
18 360 1200
16 600 2000
14 900 3000

Note 1:

Note 2: Shielded cable may be required in installations where cable trays or conduit runs include high

5.2 Sensor Location

Selection of physical sensor location is critical to the overall safe performance of the product. Five factors
play an important role in selection of sensor locations:

(1) Density of the gas to be detected
(2) Most probable leak sources within the industrial process
(3) Ventilation or prevailing wind conditions
(4) Personnel exposure
(5) Maintenance access

Density - Placement of sensors relative to the density of the target gas is such that sensors for the detection
of heavier than air gases should be located within 2-4 feet of grade as these heavy gases will tend to settle
in low lying areas. For gases lighter than air, sensor placement should be 4-8 feet above grade in open
areas or in pitched areas of enclosed spaces. Give consideration to easy access by maintenance personnel
as well as the consequences of close proximity to contaminants that may foul the sensor prematurely.

This wiring table is based on stranded tinned copper wire and is designed to serve as a reference only.

voltage lines or other sources of induced interference.

Leak Sources - Most probable leak sources within an industrial process include flanges, valves, and tubing
connections of the sealed type where seals may either fail or wear. Other leak sources are best determined

Detcon Model DM-434B Oxygen Sensor PG.6

by facility engineers with experience in similar processes.

EYS

Seal

Fitting

Drain

“T”

Plug any unused ports.

4 3/4"

3/4" NPT

1/4" Dia.

Mounting Holes

7 1/2"

6 1/8"
5 1/2"

3/4" NPT

Rain

Shield

2"

2 1/8"

Ventilation - Normal ventilation or prevailing wind conditions can dictate efficient location of gas sensors
in a manner where the migration of gas clouds is quickly detected.

Personnel Exposure - The undetected migration of gas clouds should not be allowed to approach concen­trated personnel areas such as control rooms, maintenance or warehouse buildings. A more general and
applicable thought toward selecting sensor location is combining leak source and perimeter protection in
the best possible configuration.

Note: In all installations, the sensor in stainless steel housing points down relative to grade (Fig. 1).

Improper sensor orientation will result in false reading and permanent sensor damage.

Figure #1

5.3 Local Electrical Codes

Sensor and transmitter assemblies should be installed in accordance with all local electrical codes. Use
appropriate conduit seals. Drains & breathers are recommended. The sensor assemblies are designed to
meet NEC and CSA requirements for Class I; Groups B, C, D; Div. 1 environments.

Note: An appropriate conduit seal must be located within 18" of the sensor assembly. Crouse Hinds type

EYS2, EYD2 or equivalent are suitable for this purpose.

5.4 Installation Procedure

a) Remove the junction box cover and un-plug the control transmitter by pulling it out via the pull ring.
b) Securely mount the sensor junction box in accordance with recommended practice. See dimensional

drawing (Fig. 2).

Figure #2

Detcon Model DM-434B Oxygen Sensor PG.7

c) Terminate 2 conductor field wiring to the sensor terminal board observing correct polarity in accor-

1234

WHT

BLU

Remote Transmitter

DM-434-RT

Remote Sensor

DM-434-RS

WHT

BLK

YEL

BLU

BLU

W

HT

MA

S

ensor

To Controller

Te rm i na l s

+

VDC

VDC Common

ance with the detail shown in figure 3.

d

Figure #3

d) Replace the plug-in transmitter module and the junction box cover.

5.5 Remote Mounting Applications

Some sensor mounting applications require that the gas sensor head be remotely mounted away from the
sensor transmitter. This is usually true in instances where the gas sensor head must be mounted in a loca­tion that is difficult to access. Such a location creates problems for maintenance and calibration activities.
Detcon provides the DM-434B sensor in a remote-mount configuration in which the sensor (Model DM­434-RS) and the transmitter (Model DM-434-RT) are provided in their own condulet housing and are inter­faced together with a four conductor cable. Reference figure 3A below for wiring diagram.

Figure #3A

Detcon Model DM-434B Oxygen Sensor PG.8

6.0 START UP

T

E

X

A

S

H

O

U

S

T

O

N

SIGNAL

DM-434B

ZERO

FINE

COARSE

+

0-25%

O

2

detcon inc.

detcon inc.

Upon completion of all mechanical mounting and termination of all field wiring, apply system power and
observe the following normal conditions:

) Detcon electronic controller “Fault” LED is off.

a
b) A temporary upscale reading may occur as the sensor powers up. This upscale reading will clear to

about 20.9% within a few minutes of turn-on, assuming there is no oxygen deficient condition in the
area of the sensor.

Initial Operational Tests

After a warm up period has been allowed for, the sensor should be checked to verify reliable sensitivity to O2 gas.

Material Requirements

* Digital volt meter
* Jewelers type screwdriver
* Detcon PN 943-000006-132 threaded calibration adapter
* Span Gas containing the 100% nitrogen standard at a controlled flow rate of 500 ml/min.

a) Remove the junction box cover.
b) Measure the voltage between signal test points: normal atmospheric oxygen concentration is 20.9% =

174 mv DC.
c) If applicable, remove the rain shield or splash guard from the sensor housing.
d) Attach the calibration adapter to the threaded sensor housing. Apply the test gas at a controlled flow rate of

500 ml/min. Observe that the signal voltage increases to a level of 60 mV DC or lower.
e) Remove the test gas and observe that the signal increases back to 20.9% ±2% of scale (0.5% O2).

Initial operational tests are complete. Detcon Model series DM-434B sensors are pre-calibrated prior to
shipment and will, in most cases, not require significant adjustment on start up. However, Detcon recom­mends that a complete calibration test and adjustment be performed within 24 hours of installation. Refer
to calibration instructions in later text.

7.0 CALIBRATION PROCEDURE

7.1 Material Requirements

* Digital volt meter
* Jewelers type screwdriver
* Detcon PN 943-000006-132 threaded calibration adapter
* Span Gas containing 100% nitrogen at a controlled flow rate of 500 ml/min.

Detcon Model DM-434B Oxygen Sensor PG.9

7.2 Calibration

) Declassify the area around the sensor.

1

2) Remove the junction box cover.

3) Measure the voltage between signal test points. If necessary, adjust the “fine” and/or “coarse” span

potentiometer(s) to achieve a reading of 174 mV DC.

4) If applicable, remove the rain shield or splash guard from the sensor housing.

5) Attach the calibration adapter to the threaded sensor housing.

6) Apply the test gas at a controlled flow rate of 500 ml/min. Wait 2-3 minutes for signal stability.

7) Use the “zero” potentiometer to adjust the signal to a reading of 40 mV DC.

8) Remove the gas standard and calibration adapter. Observe that the signal increases back to 174 mV DC

within 3-5 minutes. Make any needed adjustments to the “fine” and/or “coarse” span potentiometer.

Note: Because there is interaction between the span and zero functions, it may be necessary to repeat steps 5 through 8.

Calibration is complete. Replace the rain shield and junction box cover.

7.3 Calibration Notes

Detcon Model DM-434B sensors provide a signal output of 4-20 mA DC which corresponds to 0-25% O2.
This signal is reflected by a 40-200 mV DC voltage across the signal test points. Thus, every 1% change in
oxygen concentration will be reflected by a 6.4 mv DC change in the signal as measured across the signal
test points.

7.4 Calibration Frequency

In most applications, monthly to quarterly calibration intervals will assure reliable detection. However,
industrial environments differ. Upon initial installation and commissioning, close frequency tests should
be performed, weekly to monthly. Records should be kept. Less frequent test schedules should be imple­mented based on analysis of tests prior to adjustment.

8.0 SPARE PARTS LIST

613-010000-000 Sensor rain shield
613-120000-000 Sensor splash guard
943-000006-132 Threaded Calibration Adapter
897-850400-000 NEMA 7 enclosure cover
897-850800-000 NEMA 7 enclosure less cover - 3 port
897-850700-000 NEMA 7 enclosure cover with glass lens
960-202200-000 Condensation prevention packet (replace annually).
370-399100-000 Plug in replacement O2 sensor cell
399-200000-000 Stainless steel sensor housing assembly (does not include plug in sensor)
500-005065-034 Connector board
925-345400-025 Plug in control circuit
330-X50000-000 Oxygen field replaceable plug-in sensor

Detcon Model DM-434B Oxygen Sensor PG.10

9.0 WARRANTY

Tra nsmitt er As semb ly

Rain Shield

Calibr atio n Ada pter

Sensor Connector Board

Enclosure Cover

Enclosure

C

ondensation
Prevention Packet
(replace annually)

O

2 Replacement Cell

O

2 Sensor Housing Assembly

2

-56 x 3/16 (x3)

Remove to Replace

O2 Sensor

Detcon, Inc., as manufacturer, warrants each new O2 plug-in sensor cell, for a two year period under the
conditions described as follows: The warranty period begins on the date of shipment to the original pur­chaser and ends two years thereafter. The sensor cell is warranted to be free from defects in material and
workmanship. Should any sensor fail to perform in accordance with published specifications within the
warranty period, return the defective part to Detcon, Inc., 3200 Research Forest Dr., Suite A-1, The
Woodlands, Texas 77381, for necessary repairs or replacement.

10.0 SERVICE POLICY

Detcon, Inc., as manufacturer, warrants under intended normal use each new sensor signal transmitter to
be free from defects in material and workmanship for a period of two years from the date of shipment to
the original purchaser. Detcon, Inc., further provides for a five year fixed fee service policy wherein any
failed transmitter shall be repaired or replaced as is deemed necessary by Detcon, Inc., for a fixed fee of
$35.00. The fixed fee service policy shall effect any factory repair for the period following the two year
warranty and shall end five years after expiration of the warranty. All warranties and service policies are
FOB the Detcon facility located in The Woodlands, Texas.

Shipping Address: 3200 Research Forest Dr., Suite A-1, The Woodlands, Texas 77381

Mailing Address: P.O. Box 8067, The Woodlands, Texas 77387-8067

phone [phone] • fax [phone] • www.detcon.com • [e-mail]

Detcon Model DM-434B Oxygen Sensor PG.11