3.6 Start Up .............................................................................................................................................. 13
3.9.3 Other Alarm Functions ............................................................................................................... 17
3.10 Program Features ................................................................................................................................ 18
3.14 Spare Parts List ................................................................................................................................... 22
3.16 Service Policy ..................................................................................................................................... 23
Table 1 Interference Data .................................................................................................................................. 4
Table 2 Field wiring Table ................................................................................................................................ 6
Mailing Address: P.O. Box 8067, The Woodlands Texas 77387-8067
DM-634C O2 Sensor Instruction Manual iv
Page 5
DM-634C Oxygen Sensor Assembly
3.0 Description
Detcon MicroSafe™ Model DM-634, oxygen deficiency sensors are non-intrusive “Smart” senso rs 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 come with two different outputs: analog 4-20 mA, and serial RS-
485. These outputs allow for greater flexibility in the system integration and installation. The microprocessorsupervised electronics are packag ed as a plug-in 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 the
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 elect rode, galvanic metal air battery type cell, which is housed as a fiel d
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 operatin g temperature range -4° to +12 2° Fahrenheit. The sensor is warr anted
for two year and has an expected service life of up to two years in ambient air at 20.9% oxygen.
The control circuit is microprocesso r based and is packaged as a pl ug-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.
Figure 2 Microprocessor Control Circuit
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 t he normally open or normally closed relay contacts.
The sensors are packaged in a cast me tal explosion proof enclosure. The enclosure is fitted with a threaded
cover that has a glass lens window. Mag netic program switches located behind the transmitter module face
plate are activated through the lens window via a hand-held magnetic programming tool allowing nonintrusive operator interface with the sensor. All calibration and alarm level adjustments can be accomplished
without removing the cover or declassif ying the area. Electrical classification is
Class I; Groups B, C, D; Div. 1.
Figure 4 Explosion proof encl os u re s
3.1 Principle of Operation
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 adso rbed into the electroly te solution a cu rrent 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.
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 capab le of operating outside these temperatures, perfo rmance 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 deter mine number and location of sen sors. The sen sors are gener ally
located 2 - 4 feet above grade.
3.2.2 Interference Data
Table 1 Interference Data
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
Power Consumption Normal Operation = 28mA (<3/4 watt); Full Alarm = 85mA (2 watt)
Operating software is menu listed with o p erato r in terface vi a the t wo magnetic pr og ram swit ches l oc ated un der
the face plate. The two switches are ref erred to as “PGM 1” and “PGM 2”. Th e menu list consists of 3 items
which include sub-menus as indicated below. (Note: see Figure 14 at t he end of the manual for a complete
software flowchart.)
1. Normal Operation
a) Current Status
2. Calibration Mode
a) Span
3. 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 cu rrent status of the sensor and gas concentration and app ears 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 zero and span adjustments. “2 - SPAN”
The default span adjustment is set at 20.9% which is the normal atmospheric concentration of O2. Span gas
concentrations other than 20.9 % may be used. Refer to section 3.4.7 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.
The program mode provides a program status menu (Vi ew Program Status) to check operational parameters
and allows for the selection of the calibration gas level setting.
3.4.4 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 i tem appears as: “ALM1 SET @ xx.x%”
*The alarm firing direction of alarm 1. Th e menu item appears as: “ALM1 DESCENDING” or ascending.
*The alarm relay latch mode of alarm 1. Th e 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. Th e menu item appears as: “ALM2 DESCENDING” or ascending.
*The alarm relay latch mode of alarm 2. Th e 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
Note 1: This wiring table is based on stranded tinned copper wire and is designed to serve
as a reference only.
Note 2: Shielded cable may be requir ed in installations where cable trays o r conduit runs
include high voltage lines or other sources of induced interference.
AWG
Meters
Feet
20
240
800
18
360
1200
16
600
2000
14
900
3000
*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 @ ##”
*The estimated remaining sensor life. The menu item appears as: “SENSOR LIFE 100%”
3.4.5 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%”
3.4.6 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%”
3.4.7 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/g as sensor devices is directly relative to proper location and installation
practice.
3.5.1 Field Wiring Table (4-20 mA output)
Detcon MicroSafe™ O2 sensor assemblies require three conductor connection between power supplies and
host electronic controllers. Wiring designators are + (DC), – (DC), and mA (sensor sign al). 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
Table 2 Field wiring Table
The RS-485 (if applicable) requires 2 4 gauge, two conductor, shi elded, 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 A & B (IN) and A & B (OUT).
Note: For products utilizing the aluminum junction box option, the conduit seal shall be
enclosure. Crouse Hinds type EYS2, EYD2 or equivalent are suitable for this purpose.
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
Density - Placement of sensors relative to the d ensity of the target gas is such that sensors for the detection o f
heavier than air gases should be located within 2-4 feet of g rade as these heavy gases wil l 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 - Most probable leak sour ces 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 by
facility engineers with experience in similar processes.
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 person nel 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.
placed at the entry to the junction box (see Figure 6 as an example). For products utilizing
the stainless steel junction box option, the conduit seal shall be placed within 18” of the
3.5.3 Local Electrical Codes
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.
NOTE: For products utilizing the aluminum junction box option, the conduit seal shall be
enclosure. Crouse Hinds type EYS2, EYD2 or equivalent are suitable for this purpose.
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.
Figure 6 Typical Installation
placed at the entry to the junction box (see Figure 6 as an example). For products utilizing
the stainless steel junction box option, the conduit seal shall be placed within 18” of the
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 outward.
b) Securely mount the sensor junction box in accordance with recommended practice. See
dimensional drawing (Figure 7).
c) Observing correct polarity, terminate 3 conductor field wiring, RS-485 wiring, and applicable
alarm wiring to the 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.
d) Position gold plated jumper tabs located on the connector board in accordance with desired
Form C dry con- tact outputs: NO = Normally Open; NC = Normally closed (see Figure 8).
NOTE: If a voltage signal output is desired in place of the 4-20mA output, a 1/4 watt
linear signal corresponds to 0-100% of scale (see Figure 8).
5.5"
6.1"
5.825"
7.92"
2"
0.5"
4.65"
Wall (or other
mounting surface
Splash Guard
O2 Sensor
Cal Port
1/4" Mounting holes
8-32 tapped
ground point
3/4" NPT Ports
resistor must be installed in position R1 of the terminal board. A 250Ω resistor will
provide a 1-5V output (– to mA). A 1 00Ω resistor will provide a .4-2V output, etc. This
e) Pro
gram the alarms via the gold plated jumper tab positions located on the CPU board (see
Figure 9). Alarm 1 and Alarm 2 have three jumper programmable functions: latching/nonlatching relays, normally energized/normally de-energized relays, an d ascending/descending
alarm set points.
The fault alarm has two jumper programmable functions: latching/non-latching relay, and normally
energized/normally de-energized relay. The default settings of the alarms (jumpers removed) are n ormally deenergized relays, non-latching relays, and alarm points that activate during descending gas conditions.
Jumper Programmable Alarm Outputs
Normally Open or Normally Closed
Optional Voltage
Developing Resistor
Use 250ohm 1/4W
R1
Fault
ALM2
ALM1
If a jumper tab is installed in the latch position, that alarm relay will be in the latching mode. The latching
mode will latch the alarm after alar m conditions have cleared until the alarm reset fu nction 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 activ ate the alarm relay when there is no alarm condit ion and deenergize 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 conditi on.
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 concen tration detected is greater than or equal to the
alarm set point. The descending mode (jumper removed) will cause an al arm 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 8).
Preamp Board - Side View
RS-485 ID Set Dip Switches
SW1
SW2
f) If applicable, set the RS-485 ID number via the two rotary dip switches located on the pre-amp board
(see Figure 10). 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 jeweler’s screwdriver to set th e rotary dip switches according to the table listed on t he
following page. If RS-485 communications are not used, leave the dip switches in the default position
which is zero/zero (0)-(0)
Note: All alarms will be disabled for 1 minute after power up. In the event of power failure, the
alarm disable period will begin again once power has been restored.
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 temporar y 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 reliab le 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 housi ng. Apply the test gas at a controlled flow
rate of 500 ml/m. Observe that the LCD display decreases to a level of 3% or less.
b) Remove th e test gas and observe that the LCD display increases b ack to 20.9% ±2% of scale (0.5%
O2).
c) If alarms are activated d uring the test, and have been programmed fo r latching operation, reset them
according to the instructions in section 3.9.2.
Initial operational tests are complete. D etcon 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 PN 327-000000-000 MicroSafe™ Programming Magnet
* Detcon PN 613-120000-000 Threaded Calibration Adapter
* Test gas containing 100% nitrogen at a controlled flow rate of 500ml/min.
Programming Magnet Operating Instructions
Operator interface to MicroSafe™ gas detection products is via magnetic switches located behind the
transmitter face plate. DO NOT remove the glass len s cover to calibrate or change programming parameters.
Two switches labeled “PGM 1” and “PGM 2” allow for complete calibration and alarm level p rogramming
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 11) is used to operate the switches. Switch action is d efin ed
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 12.
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.
NOTE 1: Before performing an ambient air O2 span calibration, be sure there is no
oxygen deficient condition present.
CAUTION: Verif ication of the correct calibration gas level setting and calibratio n span
gas concentration is required before “span” calibration. These two numbers must be equal.
Figure 11 Magnetic Programming Tool
3.7.1 Calibration Procedure - Span
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 co ncentrations may be used as long as they fall with in 15.0% to
25.0% O2. However, any alternate span g as 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 ind icated 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”, and 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, and Set Cal Level.
NOTE 1: If the circuitry is unable to adjust th e span to the proper setting the sensor will
FAULT” (see section 3.7.3).
Figure 12 Programming Locations
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
automatically return to normal operation in 30 seconds.
f) From the calibration menu “2-SPAN” 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.
enter into the calibration fault mode which wi ll cause the display to altern ate between the
sensor’s current status reading and the calibration fault screen which appears a s: “CAL
3.7.2 Additional Notes
1. Upon entering the calibration menu, the 4-20 mA signal drops to 2 mA and is held at this level until
you 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 and cause the display to alternate between the sensor’s
current status reading and the calibratio n fault screen which appears as: “CAL F AULT” If thi s occurs
you may attempt to recalibrate by entering the calibration menu as described in section 3.7.1a. If the
sensor fails again, defer to technical trouble shooting.
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
soft- ware version number of the program, as w ell as the current alar m settings, calibratio n 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 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.
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.
1. The gas type, range of detection and software version number. The menu item appears as:
“O2 0-25 V528J”
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”
The alarm relay latch mode of alarm 2. The men u item appears as: “ALM2 LATCHING”
8.
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. B The alarm relay energize state of the fault alarm. The menu i tem 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 app ear s as: “SENSOR LIFE 100%”
c) Exit back to normal operations by holding the programming magnet over “PGM 2” for 3 seconds, or
automatically return to normal operation in 30 seconds.
Both alarm 1 and alarm 2 levels are f actory set prior to shipment. Al arm 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 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 op tions are: View Program Stat us, Set Alarm 1 Level, S et Alarm 2
Level. and Set Cal Level. back to normal operations by holding the programming magnet over “PGM
2” for 3 seconds, or automatically return to normal operation in 30 seconds.
b) ALARM 1 LEVEL From the programming menu scroll to the alarm 1 level listing. The menu item
appears as: “SET ALARM 1 LEVEL”. Enter the menu by holding the programming magnet
stationary over “PGM 1” for 3 seconds unt il the display reads “SET ALM1 @ 19.5%”, then withdraw
the magnet. Use the programming magnet to make an adjustment to “PGM 1” to in crease 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 From the programming menu scroll to the alarm 2 level listing. The menu item
appears as: “SET ALARM 2 LEVEL”. Enter the menu by holding the programming magnet
stationary over “PGM 1” for 3 seconds unt il 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
automatically return to normal operation in 30 seconds.
3.9.2 Alarm Re set
An alarm condition will cause the applicable al arm to activate its corresponding relay and LED. If alar m 1,
alarm 2, or fault alarms have been programmed for l atching relays, an alarm reset fun ction must be activated
to reset the alarms after an alarm co ndition 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 b e 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 programmabl e 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.
Detcon MicroSafe™ toxic gas sensor s incorporate a comprehensive program to accommodate easy operator
inter- face and fail-safe operation. Prog ram 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 2 5.0% 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 di splay 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 avai lable. Contact the
Detcon factory for specific protocol requirements. Communication is two wire, half duplex 485, 9600 baud, 8
data bits, 1 stop bit, 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 o n
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 th e only code supported by the transmitter . Each transmitter contains 6
holding registers which reflect its current status.
Register# High Byte Low Byte
40001 Detectable Range
i.e. 100 for 0-100ppm, 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 No t used, always 0
Bit 6 No t used, always 0
Bit 5 No t used, always 0
Bit 4 No t used, always 0
Bit 3 1 Unit is in calibration 0-Normal operation
Bit 2 1-Alarm 2 is in ascending 0-Alarm 2 is descending
Bit 1 1-Alarm 2 is normally energized 0-Alarm 2 is normally de-energizing
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 in 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 energizing 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 fo r devices #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 for devices #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 20 0001 0100
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 it, no parity, half duplex 485.
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 t his characteristic, however temperature extremes may still cause a
shift in the contrast. Display co ntrast can be adjusted by the user if nece ssary. However, ch anging 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 jeweler’s screwdriver to turn the contrast
adjust screw located beneath the metalli c face plate. The adjustment location is marked “CONTRAST”. See
Figure 12 for location.
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 l evel 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.
Detcon, Inc., as manufacturer, warrants each new p lug-in O2 sen sor 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., 4055 Technology Forest Blvd. Suite 100,
The Woodlands, Texas 77381, for necessary repairs or replacement.
3.16 Service Policy
Detcon, Inc., as manufacturer, warrants under intended normal use each new MicroSafe™ plug-in control
circuit to be free from defects in material and wo rkman ship fo r a perio d o f two years fro m the d ate of ship ment
to the original purchaser. Detcon, Inc., further provides for a fiv e 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 five year s after expiration of the warranty. All war ranties and serv ice policies are F OB
the Detcon facility located in The Woodlands, Texas.
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 of magnet
inc - Increase
dec - Decrease
# - numeric value