Page 1
detcon inc.
™
Detcon MicroSafe
DM-634 Oxygen Deficiency Sensor (0-25% O2)
Operator’s Installation & Instruction Manual
June 18,2009 • Document #2016T • Version 6.5
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Table of Contents
3.0 Description
3.1 Principle of Operation
3.2 Application
3.3 Specifications
3.4 Operating Software
3.5 Installation
3.6 Start-up
3.7 Calibration
3.8 Status of Programming: Alarms, Calibration Level, RS-485 ID, and Sensor Life
3.9 Programming Alarms
3.10 Program Features
3.11 RS-485 Protocol
3.12 Display Contrast Adjust
3.12A Trouble Shooting Guide
3.13 Spare Parts List
3.14 Warranty
3.15 Service Policy
3.16 Software Flow Chart
Detcon Model DM-634 Oxygen Sensor PG.2
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3.0 DESCRIPTION
Construction of Galvanic Cell
Cathode
Anode
Electrolyte
Solution
Diffusion Barrier
Air Supply
Load
Resistor
Detcon MicroSafe™ Model DM-634, oxygen deficiency sensors are non-intrusive “Smart” sensors designed to
detect and monitor O2 in air over the range of 0-25%. One of the primary features of the sensor is its method of
automatic calibration which guides the user through each step via instructions displayed on the backlit LCD. The
sensor features field adjustable, fully programmable alarms and provides relays for two alarms plus fault as standard.
The sensor comes with two different outputs: analog 4-20 mA, and serial RS-485. These outputs allow for greater
flexibility in system integration and installation. The microprocessor supervised electronics are packaged as a plugin module that mates to a standard connector board. Both are housed in an explosion proof condulet that includes
a glass lens window which allows for the display of sensor readings as well as access to the sensor’s menu driven features via a hand-held programming magnet.
3.0.1 Sensor Technology
The sensor technology is of the two electrode, galvanic metal air battery type cell, which is housed as a f ield
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 two year and has an
expected service life of up to two years in ambient air at 20.9% oxygen
Detcon Model DM-634 Oxygen Sensor PG.3
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3.0.2 Microprocessor Control Circuit
detcon inc.
P
rogram Switch #2
FLT
A
LM
1CAL
MicroSafe™ O2 Gas Sensor
H
OUSTO N, T EXA S
PGM 2
PGM 1
A
LM
2
MODEL DM-634
CONTRAST
Alarm & Cal LEDs
Program Switch #1
Menu Driven Display
P
lug-in Microprocessor Control Circuit
Display Contrast Adjust
NC
ALARM 1
WHT
BLK
YEL
BLU
MA
VDC Power In
NO
NC
NO
NC
NO
NO/NC
COM
NO/NC
COM
NO/NC
COM
FAULT ALM- 2 ALM-1
Alarm Dry Contacts
ALARM 2
FAULT
R1
A
B
A
B
4-20 mA Output
RS-485 In
RS-485 Out
Optional Voltage
Developing Resistor
Use 250 ohm 1/4w
JUMPERS
UN-USED
Jumper Programmable Alarm Outputs
Normally Open or Normally Closed
Sensor
Place un-used alarm programming
jumper tabs here
The control circuit is microprocessor based and is packaged as a plug-in field replaceable module, facilitating easy
replacement and minimum down time. Circuit functions include a basic sensor pre-amplifier, on-board power supplies, microprocessor, back lit alpha numeric display, alarm status LED indicators, magnetic programming switches,
an RS-485 communication port, and a linear 4-20 mA DC output.
3.0.3 Base Connector Board
The base connector board is mounted in the explosion proof enclosure and includes: the mating connector for the
control circuit, reverse input and secondary transient suppression, input filter, alarm relays, lugless terminals for all
field wiring, and a terminal strip for storing unused programming jumper tabs. The alarm relays are contact rated 5
amps @ 250 VAC, 5 amps @ 30 VDC and coil rated at 24 VDC. Gold plated program jumpers are used to select
either the normally open or normally closed relay contacts.
3.0.4 Explosion Proof Enclosure
The sensors are packaged in a cast metal explosion proof enclosure. The enclosure is fitted with a threaded cover
that has a glass lens window. Magnetic program switches located behind the transmitter module face plate are activated through the lens window via a hand-held magnetic programming tool allowing non-intrusive operator interface with the sensor. All calibration and alarm level adjustments can be accomplished without removing the cover
or declassifying the area. Electrical classification is Class I; Groups B, C, D; Div. 1.
Detcon Model DM-634 Oxygen Sensor PG.4
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3.1 PRINCIPLE OF OPERATION
Functional
Block
Diagram
Functional
Block
Diagram
Analog 4-20 mA Out
Power In
R
elays Out
P
re-Amp Display
T
emperature
Compensation
A
larm & Fault
Relays
R
S-485 & 4-20mA
M
icro-
processor
Tran smit ter
P
ower Supply
Sensor
Element
I/O Circuit
Protection
S
erial RS-485 Out
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 concentration and reverses with lower
concentrations. The quick response of the cell results in continuous monitoring of ambient air conditions.
3.2 APPLICATION
Model DM-634 MicroSafe™ sensors are designed to detect and monitor oxygen deficiency in ambient air in the range
of 0-25%. Minimum sensitivity and scale resolution is 0.1%. 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.
3.2.1 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.
3.2.2 Interference Data
Methane 100% = 0
Hydrocarbons 100% = 0
Hydrogen 100% = < -2%
Carbon Monoxide 20% = < -0.5%
3.3 SPECIFICATIONS
Method of Detection
Air battery diffusion/adsorption
Electrical Classification
Class I; Groups B, C, D; Div. 1.
Response Time (T90)
T90 < 20 seconds
Clearing Time
90% < 20 seconds
Repeatability
± 2% FS
Range
0-25% O2
Operating Temperature
-4° to +122° F
Accuracy
± 2% FS
Sensor Warranty
2 year conditional
Detcon Model DM-634 Oxygen Sensor PG.5
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Power Consumption
Normal operation = 28 mA (<3/4 watt); Full alarm = 85 mA (2 watts)
Output
3 relays (alarm 1, alarm 2, and fault) contact rated 5 amps @ 250 VAC, 5 amps @ 30 VDC;
Linear 4-20 mA DC; RS-485 Modbus™
Input Voltage
22.5-28 VDC
3.4 OPERATING SOFTWARE
Operating software is menu listed with operator interface via the two magnetic program switches located under the
face plate. The two switches are referred to as “PGM 1” and “PGM 2”. The menu list consists of 3 items which
include sub-menus as indicated below. (Note: see the end of this manual for a complete software flow chart.)
01. Normal Operation
a) Current Status
02. Calibration Mode
a) Span
03. Program Menu
a) Program Status
b) Alarm 1 Level
c) Alarm 2 Level
d) Set Calibration Level
3.4.1 Normal Operation
In normal operation, the display tracks the current status of the sensor and gas concentration and appears as:
“20.9 % O2”. The mA current output corresponds to the monitoring level of 0-25% O2 = 4-20 mA.
3.4.2 Calibration Mode
Calibration mode allows for sensor span adjustments. “2-SPAN”
The default span adjustment setting is 20.9% which is the normal atmospheric concentration of O2. Span gas concentrations other than 20.9% may be used. Refer to section 3.4.3.4 for details. “AUTO SPAN”
3.4.3 Program Mode
The program mode provides a program status menu and allows for the adjustment of alarm set point levels and the
programming of the calibration gas level setting.
3.4.3.1 Program Status
The program status scrolls through a menu that displays:
* The gas type, range of detection and software version number. The menu item appears as: “O2 0-25 V528J”
* The alarm set point level of alarm 1. The menu item appears as: “ALM1 SET @ xx.x%”
* The alarm firing direction of alarm 1. The menu item appears as: “ALM1 DESCENDING” or ascending.
* The alarm relay latch mode of alarm 1. The menu item appears as: “ALM1 NONLATCHING” or latching.
* The alarm relay energize state of alarm 1. The menu item appears as: “ALM1 DE-ENERGIZED” or energized.
* The alarm set point level of alarm 2. The menu item appears as: “ALM2 SET @ xx.x%”
* The alarm firing direction of alarm 2. The menu item appears as: “ALM2 DESCENDING” or ascending.
* The alarm relay latch mode of alarm 2. The menu item appears as: “ALM2 LATCHING” or nonlatching.
* The alarm relay energize state of alarm 2. The menu item appears as: “ALM2 DE-ENERGIZED” or energized.
* The alarm relay latch mode of the fault alarm. The menu item appears as: “FLT NONLATCHING” or latching.
* The alarm relay energize state of the fault alarm. The menu item appears as: “FLT ENERGIZED” or de-energized.
* The calibration gas level setting. The menu item appears as: “CalLevel @ xx.x%”
* Identification of the RS-485 ID number setting. The menu item appears as: “485 ID SET @ ##”
Detcon Model DM-634 Oxygen Sensor PG.6
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* The estimated remaining sensor life. The menu item appears as: “SENSOR LIFE 100%”
3.4.3.2 Alarm 1 Level Adjustment
The alarm 1 level is adjustable from 2.5% to 22.5%. The menu item appears as: “SET ALM1 @ 19.5%”
3.4.3.3 Alarm 2 Level Adjustment
The alarm 2 level is adjustable from 2.5% to 22.5%. The menu item appears as: “SET ALM2 @ 17.5%”
3.4.3.4 Calibration Level Adjustment
The calibration level is adjustable from 15.0% to 25.0% O2. The menu item appears as: “CalLevel @ xx.x%”
3.5 INSTALLATION
Optimum performance of ambient air/gas sensor devices is directly relative to proper location and installation practice.
3.5.1 Field Wiring Table
Detcon MicroSafe™ O2 sensor assemblies require three conductor connection between power supplies and host
electronic controllers. Wiring designators are
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:
lines or other sources of induced interference.
The RS-485 (if applicable) requires 24 gauge, two conductor, shielded, twisted pair cable between sensor and host
PC. Use Belden part number 9841. Two sets of terminals are located on the connector board to facilitate serial loop
wiring from sensor to sensor. Wiring designators are
3.5.2 Sensor Location
Selection of 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) Accessibility for routine maintenance
This wiring table is based on stranded tinned copper wire and is designed to serve as a reference only.
Shielded cable may be required in installations where cable trays or conduit runs include high voltage
(4-20 mA output)
+
(DC), –(DC) , and mA(sensor signal). Maximum single conductor
A& B
(IN) and A& B(OUT).
Density
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.
Leak Sources
tions of the sealed type where seals may either fail or wear. Other leak sources are best determined by facility engineers with experience in similar processes.
- Placement of sensors relative to the density of the target gas is such that sensors for the detection of
- Most probable leak sources within an industrial process include f langes, valves, and tubing connec-
Detcon Model DM-634 Oxygen Sensor PG.7
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Ventilation
EYS
Seal
Fitting
Drain
“T”
Plug any unused ports.
manner where the migration of gas clouds is quickly detected.
- Normal ventilation or prevailing wind conditions can dictate efficient location of gas sensors in a
Personnel Exposure
sonnel 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 false reading and permanent sensor damage.
3.5.3 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.
3.5.4 Accessibility
Consideration should be given to easy access by maintenance personnel as well as the consequences of close proximity to contaminants that may foul the sensor prematurely.
In all installations, the sensor points down relative to grade (Fig. 1). Improper sensor orientation may result
- The undetected migration of gas clouds should not be allowed to approach concentrated per-
Figure #1
Note:
EYD2 or equivalent are suitable for this purpose.
3.5.5 Installation Procedure
a) Remove the junction box cover and un-plug the control circuit by grasping the two thumb screws and pulling
b) Securely mount the sensor junction box in accordance with recommended practice. See dimensional drawing (Fig. 2).
c) Observing correct polarity, terminate 3 conductor field wiring, RS-485 wiring, and applicable alarm wiring to the
d) Position gold plated jumper tabs located on the connector board in accordance with desired Form C dry con-
e) Program the alarms via the gold plated jumper tab positions located on the CPU board (see figure 4). Alarm 1
An appropriate conduit seal must be located within 18" of the sensor assembly. Crouse Hinds type EYS2,
outward.
sensor base connector board in accordance with the detail shown in Figure 3. Normally open and normally closed
Form C dry contacts (rated 5 amp @ 120VAC; 5 amp @ 30VDC) are provided for Fault, Alarm 1, and Alarm 2.
tact outputs: NO = Normally Open; NC = Normally closed (see figure 3).
Note
: If a voltage signal output is desired in place of the 4-20mA output, a 1/4 watt resistor must be installed
in position R1 of the terminal board. A 250Ω resistor will provide a 1-5V output (– to mA). A 100Ω resistor will
provide a .4-2V output, etc. This linear signal corresponds to 0-100% of scale (see figure 3).
and Alarm 2 have three jumper programmable functions: latching/non-latching relays, normally energized/normally de-energized relays, and ascending/descending alarm set points.
The fault alarm has two jumper programmable functions: latching/non-latching relay, and normally
Detcon Model DM-634 Oxygen Sensor PG.8
Page 9
energized/normally de-energized relay. The default settings of the alarms (jumpers removed) are normally de-
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"
NC
ALARM 1
WHT
BLK
YEL
BLU
MA
VDC Power In
NO
NC
NO
NC
NO
NO/NC
COM
NO/NC
COM
NO/NC
COM
FAULT ALM-2 A LM -1
Alarm Dry Contacts
ALARM 2
FAULT
R1
A
B
A
B
4-20 mA Output
RS-485 In
RS-485 Out
Optional Voltage
Developing Resistor
Use 250 ohm 1/4w
JUMPERS
UN-USED
Jumper Programmable Alarm Outputs
Normally Open or Normally Closed
Sensor
Place un-used alarm programming
jumper tabs here
energized relays, non-latching relays, and alarm points that activate during descending gas conditions.
Figure #2
Figure #3
Detcon Model DM-634 Oxygen Sensor PG.9
Page 10
If a jumper tab is installed in the latch position, that alarm relay will be in the latching mode. The latching mode
FAULT
ALARM 1
Latch
Energize
Latch
Ascending
Energize
ALARM 2
Latch
Ascending
Energize
CPU Board - Top View
Alarm Programming Jumpers
Control Circuit - Side View
CPU Board
Preamp Board - Side View
RS-485 ID Set Dip Switches
Control Circuit - Side View
Preamp Board
0
1
2
3
4
5
6
7
8
9
A
B
C
D
E
F
0
1
2
3
4
5
6
7
8
9
A
B
C
D
E
F
SW2SW1
will latch the alarm after alarm conditions have cleared until the alarm reset function is activated. The non-latching
mode (jumper removed) will allow alarms to de-activate automatically once alarm conditions have cleared.
If a jumper tab is installed in the energize position, that alarm relay will be in the energized mode. The energized
mode will energize or activate the alarm relay when there is no alarm condition and de-energize or de-activate
the alarm relay when there is an alarm condition. The de-energized mode (jumper removed) will energize or activate the alarm relay during an alarm condition and de-energize or de-activate the alarm relay when there is no
alarm condition.
If a jumper tab is installed in the ascending position, that alarm relay will be in the ascending mode. The ascending mode will cause an alarm to fire when the gas concentration detected is greater than or equal to the alarm
set point. The descending mode (jumper removed) will cause an alarm to fire when the gas concentration detected is lesser than or equal to the alarm set point. Except in special applications, O2 gas monitoring will require
alarms to fire in “DESCENDING” gas conditions.
Any unused jumper tabs should be stored on the connector board on the terminal strip labeled “Unused
Jumpers” (see figure 3).
Figure #4
f) If applicable, set the RS-485 ID number via the two rotary dip switches located on the pre-amp board (see fig-
ure 5). There are 256 different ID numbers available which are based on the hexadecimal numbering system. If
RS-485 communications are used, each sensor must have its own unique ID number. Use a jewelers screwdriver
to set the rotary dip switches according to the table listed on the following page. If RS-485 communications are
not used, leave the dip switches in the default position which is zero/zero (0)-(0).
Detcon Model DM-634 Oxygen Sensor PG.10
Figure #5
Page 11
ID# SW1 SW2
none 00
101
202
303
404
505
606
707
808
909
10 0A
11 0B
12 0C
13 0D
14 0E
15 0F
16 10
17 11
18 12
19 13
20 14
21 15
22 16
23 17
24 18
25 19
26 1A
27 1B
28 1C
29 1D
30 1E
31 1F
32 20
33 21
34 22
35 23
36 24
37 25
38 26
39 27
40 28
41 29
42 2A
ID# SW1 SW2
43 2B
44 2C
45 2D
46 2E
47 2F
48 30
49 31
50 32
51 33
52 34
53 35
54 36
55 37
56 38
57 39
58 3A
59 3B
60 3C
61 3D
62 3E
63 3F
64 40
65 41
66 42
67 43
68 44
69 45
70 46
71 47
72 48
73 49
74 4A
75 4B
76 4C
77 4D
78 4E
79 4F
80 50
81 51
82 52
83 53
84 54
85 55
ID# SW1 SW2
86 56
87 57
88 58
89 59
90 5A
91 5B
92 5C
93 5D
94 5E
95 5F
96 60
97 61
98 62
99 63
100 64
101 65
102 66
103 67
104 68
105 69
106 6A
107 6B
108 6C
109 6D
110 6E
111 6F
112 70
113 71
114 72
115 73
116 74
117 75
118 76
119 77
120 78
121 79
122 7A
123 7B
124 7C
125 7D
126 7E
127 7F
128 80
ID# SW1 SW2
129 81
130 82
131 83
132 84
133 85
134 86
135 87
136 88
137 89
138 8A
139 8B
140 8C
141 8D
142 8E
143 8F
144 90
145 91
146 92
147 93
148 94
149 95
150 96
151 97
152 98
153 99
154 9A
155 9B
156 9C
157 9D
158 9E
159 9F
160 A0
161 A1
162 A2
163 A3
164 A4
165 A5
166 A6
167 A7
168 A8
169 A9
170 AA
171 AB
ID# SW1 SW2
172 AC
173 AD
174 AE
175 AF
176 B0
177 B1
178 B2
179 B3
180 B4
181 B5
182 B6
183 B7
184 B8
185 B9
186 BA
187 BB
188 BC
189 BD
190 BE
191 BF
192 C0
193 C1
194 C2
195 C3
196 C4
197 C5
198 C6
199 C7
200 C8
201 C9
202 CA
203 CB
204 CC
205 CD
206 CE
207 CF
208 D0
209 D1
210 D2
211 D3
212 D4
213 D5
214 D6
ID# SW1 SW2
215 D7
216 D8
217 D9
218 DA
219 DB
220 DC
221 DD
222 DE
223 EF
224 E0
225 E1
226 E2
227 E3
228 E4
229 E5
230 E6
231 E7
232 E8
233 E9
234 EA
235 EB
236 EC
237 ED
238 EE
239 FF
240 F0
241 F1
242 F2
243 F3
244 F4
245 F5
246 F6
247 F7
248 F8
249 F9
250 FA
251 FB
252 FC
253 FD
254 FE
255 FF
g) Replace the plug-in control circuit and replace the junction box cover.
3.5.6 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-634 sensor in a remote-mount configuration in which the sensor (Model DM-634-RS) and the transmitter
(Model DM-634-RT) are provided in their own condulet housing and are interfaced together with a four conductor
cable. Reference figure 5A below for wiring diagram.
Detcon Model DM-634 Oxygen Sensor PG.11
Page 12
1234
WHT
BLU
Remote Transmitter
DM-634-RT
Remote Sensor
DM-634-RS
WHT
BLK
YEL
BLU
Figure #5A
3.6 START UP
Upon completion of all mechanical mounting and termination of all field wiring, apply system power and observe
the following normal conditions:
a) “Fault” LED is off.
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.
NOTE:
All alarms will be disabled for 1 minute after power up. In the event of power failure, the alarm disable peri-
od will begin again once power has been restored.
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
* Detcon P/N 6132 Threaded Calibration Adapter
* Test gas containing 100% nitrogen at a controlled flow rate of 500 ml/min.
a) Attach the calibration adapter to the threaded sensor housing. Apply the test gas at a controlled f low rate of
500 ml/m. Observe that the LCD display decreases to a level of 3% or less.
b) Remove the test gas and observe that the LCD display increases back to 20.9% ±2% of scale (0.5% O2).
c) If alarms are activated during the test, and have been programmed for latching operation, reset them according to
the instructions in section 3.9.2.
Initial operational tests are complete. Detcon O2 gas sensors are pre-calibrated prior to shipment and will, in most
cases, not require significant adjustment on start up. However, it is recommended that a complete calibration test
and adjustment be performed within 24 hours of installation. Refer to calibration instructions in later text.
3.7 CALIBRATION
Material Requirements
* Detcon P/N 3270 MicroSafe™ Programming Magnet
* Detcon P/N 6132 Threaded Calibration Adapter
* Test gas containing 100% nitrogen at a controlled flow rate of 500 ml/min.
Detcon Model DM-634 Oxygen Sensor PG.12
Page 13
Programming Magnet Operating Instructions
Magnetic Programming Tool
Operator interface to MicroSafe™ gas detection products is via magnetic switches located behind the transmitter
face plate. DO NOT remove the glass lens cover to calibrate or change programming parameters. Two switches
labeled “PGM 1” and “PGM 2” allow for complete calibration and alarm level programming without removing the
enclosure cover, thereby eliminating the need for area de-classification or the use of hot permits.
A magnetic programming tool (see figure 6) is used to operate the switches. Switch action is defined as momentary contact, 3 second hold, and 30 second hold. In momentary contact use, the programming magnet is waved
over a switch location. In 3 second hold, the programming magnet is held in place over a switch location for 3 or
more seconds. In 30 second hold, the programming magnet is held in place over a switch location for 30 or more
seconds. Three and thirty second hold is used to enter or exit calibration and program menus while momentary
contact is used to make adjustments. The location of “PGM 1” and “PGM 2” are shown in figure 7.
NOTE: If, after entering the calibration or program menus, there is no interaction with the menu items for
more than 30 seconds, the sensor will return to its normal operating condition.
Figure #6
3.7.2 Calibration Procedure - Span
NOTE : Before performing an ambiennt air O2span calibration, be sure there is no oxygen-deficient condition
present.
CAUTION:
required before “span” calibration. These two numbers must be equal.
Calibration consists of entering the calibration function and following the menu-displayed instructions. The display
will ask for the application of span gas in a specific concentration. This concentration must be equal to the calibration gas level setting. The factory default setting for span gas concentration is 20.9% O2 which is the normal
atmospheric concentration. Other concentrations may be used as long as they fall within 15.0% to 25.0% O2.
However, any alternate span gas concentration value must be programmed via the calibration gas level menu before
proceeding with span calibration. Follow the instructions below for span calibration.
a) Verify the current calibration gas level setting as indicated by the programming status menu. To do this, follow
the instructions in section 3.8 and make note of the setting found in listing number 12. The item appears as
“CalGas @ xx.x %”.
b) If the calibration gas level setting is equal to your calibration span gas concentration, proceed to item “f”. If
not, adjust the calibration gas level setting so that it is equal to your calibration span gas concentration, as
instructed in items “c” through “e”.
c) Enter the programming menu by holding the programming magnet stationary over “PGM 2” for 30 seconds
until the display reads “VIEW PROG STATUS”, then withdraw the magnet. At this point you can scroll
through the programming menu by momentarily waving the programming magnet over “PGM 1” or “PGM 2”.
The menu options are: View Program Status, Set Alarm 1 Level, Set Alarm 2 Level, and Set Cal Level.
Verification of the correct calibration gas level setting and calibration span gas concentration is
Detcon Model DM-634 Oxygen Sensor PG.13
Page 14
detcon inc.
Program Switch #2
F
LT
A
LM
1
C
AL
MicroSafe™ O2 Gas Sensor
H
OUST ON, T EXA S
PGM 2
P
GM 1
A
LM
2
MODEL DM-634
CONTRAST
Alarm & Cal LEDs
Program Switch #1
Menu Driven Display
Plug-in Microprocessor Control Circuit
Display Contrast Adjust
Figure #7
d) From the programming menu scroll to the calibration level listing. The menu item appears as: “SET CAL
LEVEL”. Enter the menu by holding the programming magnet stationary over “PGM 1” for 3 seconds until
the display reads “CalGas @ ## %”, then withdraw the magnet. Use the programming magnet to make an
adjustment to “PGM 1” to increase or “PGM 2” to decrease the display reading until the reading is equal to the
desired calibration span gas concentration. Exit to the programming menu by holding the programming magnet
over “PGM1” for 3 seconds.
e) Exit back to normal operation by holding the programming magnet over “PGM 2” for 3 seconds, or automati-
cally return to normal operation in 30 seconds.
f) From the calibration menu “2-SPAN” (section 3.7.1-a) proceed into the span adjust function by holding the
programming magnet stationary over “PGM 2” for 3 seconds then withdraw the programming magnet. If no
change of Span level is desired, wait 30 seconds for menu to return to normal operation. At this point the display will ask for the application of the target gas and concentration. The display reads “APPLY xx.x %” The
xx.x here will indicate the actual concentration requested.
g) Apply the calibration test gas at a flow rate of 500 milliliters per minute. If the calibration gas level is set at
20.9% and ambient air is verified to be 20.9% (normal atmospheric concentration of O2) then do nothing at
this point. The sensor will auto calibrate to ambient air O2 concentration. After 3 minutes the sensor will auto
span to the correct reading and the display will change to “REMOVE GAS” then the display will return to
the normal operating mode.
NOTE 1: If the circuitry is unable to adjust the span to the proper setting the sensor will enter into the calibration fault mode which will cause the display to alternate between the sensor’s current status reading and the calibration fault screen which appears as: “CAL FAULT” (see section 3.7.3).
3.7.3
1. Upon entering the calibration menu, the 4-20 mA signal drops to 2 mA and is held at this level until you
Additional Notes
return to normal operation.
2. If during calibration the sensor circuitry is unable to attain the proper adjustment for span, the sensor will enter
into the calibration fault mode which will activate fault alarm functions (see section 3.10) and cause the display to
alternate between the sensor’s current status reading and the calibration fault screen which appears as: “CAL
FAULT”. If this occurs you may attempt to recalibrate by entering the calibration menu as described in section
3.7.1-a. If the sensor fails again, defer to technical trouble shooting.
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3.7.4 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. Test results should be recorded and reviewed to determine a suitable calibration interval.
3.8 STATUS OF PROGRAMMING, ALARMS, CALIBRATION LEVEL, RS-485 ID, AND SENSOR LIFE
The programming menu has a programming status listing that allows the operator to view the gas, range, and software version number of the program, as well as the current alarm settings, calibration gas level setting, RS-485 ID
number, and estimated remaining sensor life. The programming menu also allows the changing of alarm levels (see
section 3.9) and the programming of the calibration gas level setting (see section 3.7.2).
The following procedure is used to view the programming status of the sensor:
a) First, enter the programming menu by holding the programming magnet stationary over “PGM 2” for 30 sec-
onds until the display reads “VIEW PROG STATUS”, then withdraw the magnet. At this point you can
scroll through the programming menu by momentarily waving the programming magnet over “PGM 1” or
“PGM 2”. The menu options are: View Program Status, Set Alarm 1 Level, Set Alarm 2 Level, and Set Cal
Level.
b) Next, scroll to the “VIEW PROG STATUS” listing and then hold the programming magnet over “PGM 1”
for 3 seconds. The menu will then automatically scroll, at five second intervals, through the following information before returning back to the “VIEW PROG STATUS” listing.
The gas type, range of detection and software version number. The menu item appears as:
1 2 - The alarm set point level of alarm 1. The menu item appears as: “ALM1 SET @ 19.5%”
3 - The alarm firing direction of alarm 1. The menu item appears as: “ALM1 DESCENDING”
4 - The alarm relay latch mode of alarm 1. The menu item appears as: “ALM1 NONLATCHING”
5 - The alarm relay energize state of alarm 1. The menu item appears as: “ALM1 DE-ENERGIZED”
6 - The alarm set point level of alarm 2. The menu item appears as: “ALM2 SET @ 17.5%”
7 - The alarm firing direction of alarm 2. The menu item appears as: “ALM2 DESCENDING”
8 - The alarm relay latch mode of alarm 2. The menu item appears as: “ALM2 LATCHING”
9 - The alarm relay energize state of alarm 2. The menu item appears as: “ALM2 DE-ENERGIZED”
10 - The alarm relay latch mode of the fault alarm. The menu item appears as: “FLT NONLATCHING”
11 - The alarm relay energize state of the fault alarm. The menu item appears as: “FLT ENERGIZED”
12 - Calibration gas level setting. The menu appears as “CalLevel @ xx.x%”
13 - Identification of the RS-485 ID number setting. The menu item appears as: “485 ID SET @ 1”
14 - The estimated remaining sensor life. The menu item appears as: “SENSOR LIFE 100%”
c) Exit back to normal operations by holding the programming magnet over “PGM 2” for 3 seconds, or automati-
cally return to normal operation in 30 seconds.
“O2 0-25 V528J”
3.9 PROGRAMMING ALARMS
3.9.1 Alarm Levels
Both alarm 1 and alarm 2 levels are factory set prior to shipment. Alarm 1 is set at 19.5%; alarm 2 at 17.5%. Both
alarms can be set in 0.1% increments from 2.5% to 22.5%. The following procedure is used to change alarm set points:
a) First, enter the programming menu by holding the programming magnet stationary over “PGM 2” for 30 sec-
onds until the display reads “VIEW PROG STATUS”, then withdraw the magnet. At this point you can
scroll through the programming menu by momentarily waving the programming magnet over “PGM 1” or
“PGM 2”. The menu options are: View Program Status, Set Alarm 1 Level, Set Alarm 2 Level. and Set Cal
Level.
b) ALARM 1 LEVEL
From the programming menu scroll to the alarm 1 level listing. The menu item appears as:
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“SET ALARM 1 LEVEL”. Enter the menu by holding the programming magnet stationary over “PGM 1”
for 3 seconds until the display reads “SET ALM1 @ 19.5%”, then withdraw the magnet. Use the programming magnet to make an adjustment to “PGM 1” to increase or “PGM 2” to decrease the display reading until
the reading is equal to the desired alarm set point. Exit to the programming menu by holding the programming
magnet over “PGM1” for 3 seconds, or automatically return to the programming menu in 30 seconds.
c) ALARM 2 LEVEL
“SET ALARM 2 LEVEL”. Enter the menu by holding the programming magnet stationary over “PGM 1”
for 3 seconds until the display reads “SET ALM2 @ 17.5%”, then withdraw the magnet. Use the programming magnet to make an adjustment to “PGM 1” to increase or “PGM 2” to decrease the display reading until
the reading is equal to the desired alarm set point. Exit to the programming menu by holding the programming
magnet over “PGM1” for 3 seconds, or automatically return to the programming menu in 30 seconds.
d) Exit back to normal operations by holding the programming magnet over “PGM 2” for 3 seconds, or automati-
cally return to normal operation in 30 seconds.
3.9.2 Alarm Reset
An alarm condition will cause the applicable alarm to activate its corresponding relay and LED. If alarm 1, alarm 2,
or fault alarms have been programmed for latching relays, an alarm reset function must be activated to reset the
alarms after an alarm condition has cleared. To reset the alarms, simply wave the programming magnet over either
“PGM 1” or “PGM 2”, momentarily, while in normal operations mode and note that the corresponding alarm
LED(s) turn off.
3.9.3 Other Alarm Functions
Alarms are factory programmed to be non-latching, de-energized; and to fire under ascending gas conditions. The
fault alarm relay is programmed as normally energized which is useful for detecting a 24VDC power source failure.
All alarm functions are programmable via jumper tabs. Changing alarm functions requires the sensor housing to be
opened, thus declassification of the area is required. See section 3.5.4-e for details.
From the programming menu scroll to the alarm 2 level listing. The menu item appears as:
3.10 PROGRAM FEATURES
Detcon MicroSafe™ toxic gas sensors incorporate a comprehensive program to accommodate easy operator interface and fail-safe operation. Program features are detailed in this section. Each sensor is factory tested, programmed,
and calibrated prior to shipment.
Over Range
When the sensor detects gas greater than 25.0% O2, it will cause the display to flash “25.0 % O2” on and off.
Sensor Fault
If either of the wires connecting the sensor cell to the connector board should fail and cause an open circuit, the
sensor will go into a fault condition. “SENSOR FAULT”.
Calibration Fault
If during calibration the sensor circuitry is unable to attain the proper adjustment for span, the sensor will enter into
the calibration fault mode and cause the display to alternate between the sensor’s current status reading and the calibration fault screen which appears as: “CAL FAULT”.
Fail-Safe/Fault Supervision
Detcon MicroSafe™ sensors are programmed for fail-safe operation. Any fault condition will activate the fault relay,
illuminate the fault LED, and cause the display to read its corresponding fault condition: “SENSOR FAULT”, or
“CAL FAULT”. A “SENSOR FAULT” will also cause the mA output to drop to zero (0) mA.
Sensor Life
The sensor life feature is a reference based on signal output from the sensor cell. When a sensor life of 25% or less
remains, the sensor cell should be replaced within a reasonable maintenance schedule.
3.11 RS-485 PROTOCOL
Model TP-624C MicroSafe™ sensors feature Modbus™ compatible communications protocol and are addressable
via rotary dip switches for multi-point communications. Other protocols are available. Contact the Detcon factory
for specific protocol requirements. Communication is two wire, half duplex 485, 9600 baud, 8 data bits, 1 stop bit,
Detcon Model DM-634 Oxygen Sensor PG.16
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no parity, with the sensor set up as a slave device. A master controller up to 4000 feet away can theoretically poll
up to 256 different sensors. This number may not be realistic in harsh environments where noise and/or wiring conditions would make it impractical to place so many devices on the same pair of wires. If a multi-point system is
being utilized, each sensor should be set for a different address. Typical address settings are: 01, 02, 03, 04, 05, 06,
07, 08, 09, 0A, 0B, 0C, 0D, 0E, 0F, 10, 11, etc.
In most instances, RS-485 ID numbers are factory set or set during installation before commissioning. If required,
the RS-485 ID number can be set via rotary dip switches located on the pre-amp circuit board. However, any
change to the RS-485 ID number would require the sensor housing to be opened, thus declassification of the area
would be required. See section 3.5.5-f for details on changing the RS-485 ID number.
The following section explains the details of the Modbus™ protocol that the DM-634 MicroSafe™ sensor supports.
Code 03 - Read Holding Registers, is the only code supported by the transmitter. Each transmitter contains 6 holding registers which reflect its current status.
Register # High Byte Low Byte
40000 Gas type Sensor Life
Gas type is one of the following:
01=CO, 02=H2S, 03=SO2, 04=H2, 05=HCN, 06=CL2, 07=NO2, 08=NO, 09=HCL, 10=NH3, 11=LEL, 12=O2
Sensor life is an estimated remaining use of the sensor head, between 0% and 100%
Example: 85=85% sensor life
Register # High Byte Low Byte
40001 Detectable Range
i.e. 100 for 0-100 ppm, 50 for 0-50% LEL, etc.
Register #
High Byte Low Byte
40002 Current Gas Reading
The current gas reading as a whole number. If the reading is displayed as 23.5 on the display, this register would
contain the number 235.
Register #
High Byte Low Byte
40003 Alarm 1 Setpoint
This is the trip point for the first alarm.
Register #
High Byte Low Byte
40004 Alarm 2 Setpoint
This is the trip point for the second alarm.
Register #
High Byte Low Byte
40005 Status Bits Status Bits
High Byte
Bit 7 Not used, always 0
Bit 6 Not used, always 0
Bit 5 Not used, always 0
Bit 4 Not used, always 0
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Bit 3 1-Unit is in calibration 0-Normal operation
Bit 2 1-Alarm 2 is ascending 0-Alarm 2 is descending
Bit 1 1-Alarm 2 is normally energized 0-Alarm 2 is normally de-energized
Bit 0 1-Alarm 2 is latching 0-Alarm 2 is non-latching
Low Byte
Bit 7 1-Alarm 2 Relay is energized 0-Alarm 2 Relay is not energized
Bit 6 1-Alarm 1 is ascending 0-Alarm 1 is descending
Bit 5 1-Alarm 1 is normally energized 0-Alarm 1 is normally de-energized
Bit 4 1-Alarm 1 is latching 0-Alarm 1 is non-latching
Bit 3 1-Alarm 1 Relay is energized 0-Alarm 1 Relay is not energized
Bit 2 1-Fault is normally energized 0-Fault is normally de-energized
Bit 1 1-Fault is latching 0-Fault is non-latching
Bit 0 1-Fault Relay is energized 0-Fault Relay is not energized
The following is a typical Master Query for device # 8:
Field
Name HEX DEC RTU
Slave Address 08 8 0000 1000
Function 03 3 0000 0011
Start Address Hi 00 0 0000 0000
Start Address Lo 00 0 0000 0000
No. of Registers Hi 00 0 0000 0000
No. of Registers Lo 06 6 0000 0110
CRC ## #### ####
CRC ## #### ####
The following is a typical Slave Response from device # 8:
Field
Name HEX DEC RTU
Slave Address 08 8 0000 1000
Function 03 3 0000 0011
Byte Count 0C 12 0000 1100
Reg40000 Data Hi 02 2 0000 0010
Reg40000 Data Lo 64 100 0110 0100
Reg40001 Data Hi 00 0 0000 0000
Reg40001 Data Lo 64 100 0110 0100
Reg40002 Data Hi 00 0 0000 0000
Reg40002 Data Lo 07 7 0000 0111
Reg40003 Data Hi 00 0 0000 0000
Reg40003 Data Lo 0A 10 0000 1010
Reg40004 Data Hi 00 0 0000 0000
Reg40004 Data Lo 14 20 0001 0100
Reg40005 Data Hi 05 5 0000 0101
Reg40005 Data Lo 50 80 0101 0000
CRC ## #### ####
CRC ## #### ####
Additional Notes:
The calibration LED will light when the transmitter is sending a response to a Master Query.
Communications are 9600 baud, 8 data bits, 1 stop bit, No parity, half duplex 485.
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3.12 DISPLAY CONTRAST ADJUST
Detcon MicroSafe™ sensors feature a 16 character backlit liquid crystal display. Like most LCD, character contrast
can be affected by viewing angle and temperature. Temperature compensation circuitry included in the MicroSafe™
design will compensate for this characteristic, however temperature extremes may still cause a shift in the contrast.
Display contrast can be adjusted by the user if necessary. However, changing the contrast requires that the sensor
housing be opened, thus declassification of the area is required.
To adjust the display contrast, remove the enclosure cover and use a jewelers screwdriver to turn the contrast
adjust screw located beneath the metallic face plate. The adjustment location is marked “CONTRAST”. See figure 7
for location.
3.12A TROUBLE SHOOTING
Memory or Error Reports
1. Re-initialize Sensor - Unplug transmitter and re-plug transmitter then swipe magnet over PGM 1 in the first 3 seconds. This will clear the processor and recover from error state. Remember to put in all customer settings for range,
alarm and cal gas level after re-initialization.
Non-readable Display
1. If display has blue background when hot, install sunshade to reduce temperature.
2. If poor contrast, adjust contrast pot accordingly.
Nothing Displayed – Transmitter not Responding
1. Verify condulet has no accumulated water or abnormal corrosion.
2. Verify required DC power is applied to correct terminals.
3. Swap with a known-good transmitter to determine if transmitter is faulty.
Bad 4-20 mA Output or RS485 Output
1. Check that wiring is connected to correct terminal outputs.
2. Swap with a known-good transmitter to determine if transmitter is faulty.
3.13 SPARE PARTS LIST
613-120000-700 Sensor splash guard
943-000006-132 Threaded Calibration Adapter for DM
500-001794-004 Connector board
327-000000-000 Programming Magnet
897-850800-000 3 port enclosure less cover
897-850700-000 Enclosure glass lens cover
960-202200-000 Condensation prevention packet (replace annually).
370-399100-000 Plug in replacement O2 sensor cell
926-345500-025 Plug in control circuit
399-200000-000 Stainless steel sensor housing assembly (does not include plug in sensor)
3.14 WARRANTY
Detcon, Inc., as manufacturer, warrants each new plug-in O2 sensor cell (P/N 370-399100-000), 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 the sensor cell fail to perform in accordance with published specifications within the warranty
period, return the defective part to Detcon, Inc., 3200 A-1 Research Forest Dr., The Woodlands, Texas 77381, for
necessary repairs or replacement.
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3.15 SERVICE POLICY
Spash Guard
Rain Shield
Enclosure less cover
Connector Board
Calib ra ti on Adapt er
Enclosure glass lens cover
Plug-in control circuit
O2 Replacement Cell
O2 Sensor Housing Assembly
Programming Magnet
Condensation
Prevention Packet
(replace annually)
2-56 x 3/16 (x3)
Remove to Replace
O2 Sensor
Detcon, Inc., as manufacturer, warrants under intended normal use each new MicroSafe™ plug-in control circuit 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 $65.00. The fixed fee service
policy shall affect any factory repair for the period following the two year warranty and shall end f ive years after
expiration of the warranty. All warranties and service policies are FOB the Detcon facility located in The
Woodlands, Texas.
Detcon Model DM-634 Oxygen Sensor PG.20
Page 21
3.16 SOFTWARE FLOW CHART
NORMAL
OPERATION
C
ALIBRATION
P
GM2 (3)
PGM1 (M) PGM2 (M)
PGM1 (3)
SET ALM1 @ ##.#%
INC
DEC
PGM1 (3) PGM2 (M)
2-SPAN
LEGEND
PGM1 - program switch location #1
PGM2 - program switch location #2
(
M) - momentary pass of magnet
(
3) - 3 second hold of magnet
(
30) - 30 second hold of magnet
I
NC - increase
D
EC - decrease
# - numeric value
A
UTO SPAN
SET ALARM 1 LEVEL
O2 0-25 V#.#
PGM1 (3) PGM2 (M)
VIEW PROG STATUS
ALM1 SET @ ##.#%
ALM2 SET @ ##.#%
485 ID SET @ #
PGM1 (M) PGM2 (M)
PGM1 (3)
SET ALM2 @ ##.#%
INC
DEC
PGM1 (3) PGM2 (M)
SET ALARM 2 LEVEL
PGM2 (3) PGM2 (3) PGM2 (3)
SENSOR LIFE ##%
ALM1 (Firing Direction)
ALM1 (Latch State)
ALM1 (Energize State)
ALM2 (Firing Direction)
ALM2 (Latch State)
ALM2 (Energize State)
FLT (Latch State)
FLT (Energize State)
PGM1 (3) PGM1 (M)
PGM2 (30) PGM2 (M)
ALARM RESET
ALARM RESET
Shipping Address: 3200 A-1 Research Forest Dr., The Woodlands, Texas 7381
Mailing Address: P.O. Box 8067, The Woodlands, Texas 77387-8067
phone 888-367-4286, 713-559-9200 • fax 281-292-2860 • www.detcon.com • sales@detcon.com
Detcon Model DM-634 Oxygen Sensor PG.21
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