GDS Corp GASMAX EC User manual

GDS Corp.
2513 Hwy 646 Santa Fe, Texas 77510
409-927-2980 409-927-4180 (Fax) ww.gdscorp.com
Operation and Maintenance
Manual
GASMAX EC Loop-Powered Toxic Gas Monitor

GASMAX EC Operation & Maintenance Manual, Revision 3.5
Page 2
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 SÉCURITÉ, CET ÉQUIPEMENT DOIT ÊTRE UTILISÉ,
ENTRETENU ET RÉPARÉ UNIQUEMENT PAR UN PERSONNEL QUALIFIÉ. ÉTUDIER LE
MANUE D’INSTRUCTIONS EN ENTIER AVANT D’UTILISER, D’ENTRETENIR OU DE
RÉPARER L’ÉQUIPEMENT.
REVISION HISTORY
Revision 3.5.1 4/15/13 Initial rewrite for GASMAX EC
Copyright © 2013 GDS Corp. All Rights Reserved
P/N 1200-0852-01

GASMAX EC Operation & Maintenance Manual, Revision 3.5
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CONTENTS
1 SAFETY INFORMATION _______________________________________________ 8
2 GENERAL INFORMATION ______________________________________________ 9
Introduction ________________________________________________________________ 9
GASMAX Sensors ____________________________________________________________ 9
3 SPECIFICATIONS ____________________________________________________ 10
4 INSTALLATION _____________________________________________________ 11
Locating the GASMAX EC _____________________________________________________ 11
Mounting the GASMAX Instrument Enclosure ____________________________________ 11
Mounting the GASMAX emote Sensor Enclosure _________________________________ 12
Explosion Proof Installation ___________________________________________________ 12
Intrinsically Safe Installation __________________________________________________ 13
Connecting Loop Power / Signal Wiring _________________________________________ 13
Local Smart Sensor __________________________________________________________ 14
Connecting a emote Sensor __________________________________________________ 15
Initial Setup _______________________________________________________________ 16
5 CALIBRATION ______________________________________________________ 18
Calibration Overview ________________________________________________________ 18
Calibration Procedure _______________________________________________________ 19
6 OPERATION AND MAINTENANCE ______________________________________ 21
GASMAX Display Screens _____________________________________________________ 21
Data Display Screen _________________________________________________________ 21
Trend Display Screen ________________________________________________________ 22
Normal Operation __________________________________________________________ 22

GASMAX EC Operation & Maintenance Manual, Revision 3.5
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Alarm Operation – ALA M 1 and 2 _____________________________________________ 22
Alarm Operation – ALA M 3 __________________________________________________ 23
Sensor eplacement ________________________________________________________ 23
Sensor eplacement – emote Sensors _________________________________________ 25
Normal Maintenance ________________________________________________________ 25
7 USER MENUS ______________________________________________________ 26
Main Menu ________________________________________________________________ 26
System Configuration Page ___________________________________________________ 27
Measurement Name _______________________________________________________________ 27
Eunits ___________________________________________________________________________ 27
Zero (0%) ________________________________________________________________________ 27
Span (100%) ______________________________________________________________________ 27
Decimal Points ____________________________________________________________________ 27
Cal Span Value ____________________________________________________________________ 27
eadout Deadband ________________________________________________________________ 27
Track Negative ____________________________________________________________________ 27
Temp Compensation _______________________________________________________________ 28
Backup Config ____________________________________________________________________ 28
estore Config ____________________________________________________________________ 28
Upload Sensor Data ________________________________________________________________ 28
Cal Marker _______________________________________________________________________ 28
TX Sensor Life _____________________________________________________________________ 28
Alarm Settings Page _________________________________________________________ 29
Set Point _________________________________________________________________________ 29
Dead-Band _______________________________________________________________________ 29
ON Delay ________________________________________________________________________ 29
OFF Delay ________________________________________________________________________ 29
Low Trip _________________________________________________________________________ 29
Latching _________________________________________________________________________ 29
Display Event Log __________________________________________________________________ 30
Clear Event Log ___________________________________________________________________ 30

GASMAX EC Operation & Maintenance Manual, Revision 3.5
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Sensor settings page ________________________________________________________ 30
Install New Sensor _________________________________________________________________ 30
ecall Cal History __________________________________________________________________ 30
Input Type _______________________________________________________________________ 30
New Sensor ______________________________________________________________________ 30
ecent Cal _______________________________________________________________________ 30
CLOCK/DELAY SETUP Page ____________________________________________________ 31
Time ____________________________________________________________________________ 31
Date ____________________________________________________________________________ 31
Warm Up Delay ___________________________________________________________________ 31
Cal Purge Delay ___________________________________________________________________ 31
LCD CONT AST Adjustment Page ______________________________________________ 31
HELP Screen Page ___________________________________________________________ 31
DIAGNOSTICS Page __________________________________________________________ 31
Output Simulation _________________________________________________________________ 32
elay Test ________________________________________________________________________ 32
SYSTEM SECU ITY Page ______________________________________________________ 32
Contact Name ____________________________________________________________________ 32
Secure Level ______________________________________________________________________ 32
8 TECHNICIANS MENUS _______________________________________________ 33
XMITTE CONFIG Menu ______________________________________________________ 33
O2 / Toxic ________________________________________________________________________ 33
LEL / Current _____________________________________________________________________ 33
Output Zero / Span Trim ____________________________________________________________ 33
eal Time Clock ___________________________________________________________________ 33
Model ___________________________________________________________________________ 33
TECHNICAL PAGE Menu ______________________________________________________ 34
Set Balance _______________________________________________________________________ 34
Set Voltage _______________________________________________________________________ 34
Preamp Gain Set __________________________________________________________________ 35
Input Type _______________________________________________________________________ 35
Zero Cal Value ____________________________________________________________________ 36

GASMAX EC Operation & Maintenance Manual, Revision 3.5
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aw Min / Max Counts _____________________________________________________________ 36
Marker Menu _____________________________________________________________________ 36
9 TROUBLESHOOTING GUIDE ___________________________________________ 37
Toxic Sensor Indicates Fault or Overrange _______________________________________ 37
Toxic Sensor Will Not Calibrate ________________________________________________ 37
eceiving Device and GASMAX Displayed Values Don’t Match _______________________ 37
GASMAX Display Blank ______________________________________________________ 37
GASMAX Error Codes ________________________________________________________ 37
10 SPARE PARTS ____________________________________________________ 39
Display & Enclosure _________________________________________________________ 39
Sensor Head Accessories _____________________________________________________ 39
emote Sensor _____________________________________________________________ 40
11 DRA INGS AND DIMENSIONS ______________________________________ 41

GASMAX EC Operation & Maintenance Manual, Revision 3.5
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TABLE OF FIGURES
FIGU E 3-1: GASMAX EC TOXIC SENSO S .................................................................................................... 10
FIGU E 4-1: GASMAX EC EXPLOSION P OOF ENCLOSU E ........................................................................... 11
FIGU E 4-2: GASMAX EC EMOTE SENSO .................................................................................................. 12
FIGU E 4-3: GASMAX EC LOOP POWE WI ING .......................................................................................... 13
FIGU E 4-4: LOCAL SMA T TOXIC SENSO .................................................................................................. 14
FIGU E 4-5: GASMAX EC EMOTE SENSO WI ING .................................................................................... 15
FIGU E 4-6: GASMAX INT INSICALLY SAFE INSTALLATION .......................................................................... 16
FIGU E 4-7: GASMAX EC IS WI ING GUIDELINES ......................................................................................... 16
FIGU E 5-1: CALIB ATION SETUP ................................................................................................................. 19
FIGU E 5-2: CALIB ATION FLOWCHA T ...................................................................................................... 20
FIGU E 6-1: GASMAX EC DISPLAY SC EENS ................................................................................................. 21
FIGU E 6-2: GASMAX DATA DISPLAY SC EEN .............................................................................................. 22
FIGU E 6-3: GASMAX T END DISPLAY SC EEN ............................................................................................ 22
FIGU E 6-4: SENSO EPLACEMENT ............................................................................................................ 24
FIGU E 6-5: SMA T SENSO ECOGNITION SC EEN ................................................................................... 24
FIGU E 7-1: MAIN MENU FLOWCHA T ........................................................................................................ 26
FIGU E 7-2: SYSTEM CONFIG MENU ............................................................................................................ 27
FIGU E 7-3: SENSO LIFE T ANSMISSSION FO MAT ................................................................................... 28
FIGU E 7-4: ALA M SETTINGS MENU .......................................................................................................... 29
FIGU E 7-5: SENSO SETTINGS MENU ........................................................................................................ 30
FIGU E 7-6: CLOCK DELAY MENU ................................................................................................................. 31
FIGU E 7-7: CONT AST MENU ..................................................................................................................... 31
FIGU E 7-8: DIAGNOSTICS MENU ................................................................................................................ 32
FIGU E 7-9: SYSTEM SECU ITY MENU ......................................................................................................... 32
FIGU E 8-1: XMITTE CONFIG MENU .......................................................................................................... 33
FIGU E 8-2: TECHNICAL PAGE MENU ........................................................................................................... 34
FIGU E 8-3: SET GAIN TO UNITY MENU ....................................................................................................... 35
FIGU E 8-4: P EAMP GAIN SET MENU ......................................................................................................... 35
FIGU E 10-1: GASMAX EC + LOCAL SENSO SPA E PA TS .......................................................................... 39
FIGU E 10-2: GASMAX SENSO HEAD SPLASH GUA D & FLOW CELL ......................................................... 39
FIGU E 10-3: GASMAX EC EMOTE DI ECT SENSO HEAD ......................................................................... 40

GASMAX EC Operation & Maintenance Manual, Revision 3.5
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1SAFETY INFO MATION
Important – ead Before Installation
Users should have a detailed understanding of GASMAX EC operating and maintenance instructions. Use
the GASMAX EC only as specified in this manual or detection of gases and the resulting protection
provided may be impaired. ead the following WA NINGS prior to use.
WA NINGS
•The GASMAX EC gas monitor described in this manual must be installed, operated and
maintained in accordance with information contained herein. Installation in any hazardous area
must comply with all applicable restrictions, requirements and guidelines for said hazardous
areas. It is the end user customer’s final decision to ensure that the GASMAX EC is suitable for
the intended use.
•The GASMAX EC is designed and constructed to measure the level of certain gases in ambient air.
Accuracy in atmospheres containing steam or inert gases cannot be guaranteed.
•Always mount the sensor head vertically with the sensor head facing down.
•Do not paint transmitter or sensor assembly.
•Do not operate the GASMAX EC if its enclosure is damaged or cracked or has missing
components. Make sure the cover, internal PCB’s and field wiring are securely in place before
applying power.
•Do not expose the GASMAX EC to electrical shock or continuous severe mechanical shock.
Protect the GASMAX EC and related sensor assemblies from dripping liquids and high power
sprays.
•Calibrate with known target gas at start-up and check on a regular schedule, at least every 90
days. More frequent inspections are encouraged to spot problems such as dirt, oil, paint, grease
or other foreign materials on the sensor head.
•Periodically test for correct operation of the system’s alarm events by exposing the monitor to a
targeted gas concentration above the High Alarm set point.
•Use only for applications described within this manual.

GASMAX EC Operation & Maintenance Manual, Revision 3.5
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2GENE AL INFO MATION
Introduction
The GASMAX EC is a single channel fixed-point gas monitor designed to provide continuous monitoring of
toxic or combustible gases in hazardous areas. Gas values are displayed in calibrated engineering units as
well as bar graph or 30-minute trend graph format.
The GASMAX EC supports one local or remote mount sensors for
toxic gas. The advanced microcontroller, non-intrusive magnetic
interface and superior graphic LCD interface offers rapid setup,
simplified operation and enhanced diagnostics not found in previous
generation products. On-board non-volatile memory retains all
configuration data during power interruptions. A single loop-
powered 4-20 mA output allow for easy connection to control
systems or other alarm instrumentation.
Built-in user-prompted calibration makes it easy for one person to
perform calibration and maintenance without opening the enclosure
or declassifying the area. A battery-powered real-time clock and
event log allows the GASMAX EC to track calibration and alarm events for later recall on the LCD readout.
GASMAX Sensors
For toxic gases the GASMAX EC supports a wide range of electrochemical (“echem”) sensors. These
sensors use chemical reactions to sense the presence of gases such as hydrogen sulfide, chlorine, sulfur
dioxide and many others. Echem sensors output very low level signals; remote echem sensors should be
mounted no more than 15 feet from the GASMAX enclosure, the wiring should be three-conductor with
foil shield, and the wiring should be enclosed in metal conduit for maximum protection against
interference. If longer distance is required, the GASMAX offers a sensor-transmitter option for
electrochemical sensors that converts the output into a 4-20mA signal. Distances up to 500 feet are
practical with 4-20mA signals. Channel 1 on the GASMAX EC can be configured for direct echem or 4-
20mA input.
IMPO TANT: TOXIC SENSO S A E SUBJECT TO ACCELE ATED DETE IO ATION IF POWE IS NOT
SUPPLIED WITHIN 3 MONTHS OF SHIPMENT F OM GDS CO P.

GASMAX EC Operation & Maintenance Manual, Revision 3.5
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3SPECIFICATIONS
Power Input 10-30VDC at less than 0.75W
Display 64 x128 pixel LCD with engineering units, bargraph and 30-minute trend
Input Accepts microamp-level inputs from local or remote GDS Corp toxic or oxygen
deficiency sensors
Accuracy +/- 5% of full scale (typical)
Standard
Output
Two-wire 4-20mA loop powered current sink with fault and overrange indication.
Maximum loop resistance is 600 ohms with standard 24VDC supply
Temperature Electronics -40°C to +60°C. See Echem Sensor Manual for additional details
Memory On-board non-volatile memory retains all user settings
Housing Aluminum housing with epoxy paint standard; #316 stainless steel optional
Dimensions Width 5.4” (137 mm), Height 8” (203 mm), Depth 5” (127 mm)
Shipping weight 6.5 pounds (3 kg)
Approvals CSA Certified Division 1 & 2 Groups B, C, D. Suitable for explosion-proof installations
with flame arrestor. CSA Certified Division 1 & 2 Groups A, B, C, D. Intrinsically safe
when used with IS barrier #10-0263 (MTL 7787P+) or equivalent.
ATEX Certified EX II 2 G EEx d IIB + H2 T5
Warranty Two years on electronics, one year on sensor
10 Oxygen 22 Ethylene Oxide
11 Carbon Monoxide 23 Arsine
12 Chlorine 24 Silane
13 Chlorine Dioxide 25 Fluorine
14 Hydrogen 26 Phosgene
15 Hydrogen Sulfide 27 Hydrazine
16 Hydrogen Cyanide 28 Nitric Oxide
17 Hydrogen Chloride 29 Nitrogen Dioxide
18 Hydrogen Fluoride 30 Mercaptan
19 Sulfur Dioxide 31 Tetrahydrothiophene
20 Ammonia 32 Diborane
21 Ozone 33 Hydrogen Sulfide (Low H)
Figure 3-1: GASMAX EC Toxic Sensors

GASMAX EC Operation & Maintenance Manual, Revision 3.5
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4INSTALLATION
Locating the GASMAX EC
Factors such as air movement, gas density in relation to air, emission sources and environmental variables
affect correct sensor location. Air movement by fans, prevailing winds and convection should be carefully
evaluated to determine if a leak is more likely to raise gas levels in certain areas within the facility. Vapor
density of a gas determines if it will rise or fall in air when there are no significant currents. Lighter than
air gases should have the monitors mounted 12 – 18 inches (30 – 45 cm) above the potential gas leak and
heavier than air gases should be this distance below. Even though the GASMAX EC is designed for rugged
service, sensors should be protected from environmental damage from water, snow, shock, vibration and
dirt.
Mounting the GASMAX Instrument Enclosure
The GASMAX EC standard enclosure is a cast aluminum explosion-proof (NEMA 7) enclosure as shown in
Figure 4-1.
Figure 4-1: GASMAX EC Explosion Proof Enclosure
The GASMAX EC should always be mounted with the sensor head opening facing down. If necessary, a
Splash Guard (p/n 10-0205) should be attached if there is any chance that water or liquid spray could
enter the sensor opening from below. Be sure to leave sufficient room (~ 12”) below the sensor head to
allow easy access for attachment of a Calibration Cup and / or removal of the sensor head cover for
sensor replacement.

GASMAX EC Operation & Maintenance Manual, Revision 3.5
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Mounting the GASMAX emote Sensor Enclosure
The GASMAX EC remote sensor consists of a cast aluminum explosion-proof junction box and stainless
steel sensor head (see Fig. 4-2). The junction box contains a PCB with connection point for the sensor
head cable and wiring terminals for the three-wire connection to the GASMAX EC display enclosure.
Fittings are ¾” NPT. The sensor head should ALWAYS be mounted vertically as shown, and GDS Corp
recommends side entry for all conduit runs.
Figure 4-2: GASMAX EC Remote Sensor
Explosion Proof Installation
GASMAX EC monitors with standard explosion-proof sensor heads are certified for use in Class 1 Division 1
hazardous areas. Installation in these areas should follow best industry standard practices and all
appropriate electrical codes. Generally, these codes require rigid metal conduit, poured seals and other
installation elements necessary to ensure safety. In all cases, GDS Corp recommends the GASMAX EC be
mounted vertically with the sensor opening facing down. If there is a possibility that water or other liquid
may be present, GDS Corp further recommends the installation of a Splash Guard (p/n 10-0205) to protect
the sensor from damage. For maximum protection against interference or electrical surge, the GASMAX
EC enclosure and conduit must be properly grounded.

GASMAX EC Operation & Maintenance Manual, Revision 3.5
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Intrinsically Safe Installation
GASMAX EC monitors with standard explosion-proof sensor heads, or with sensor heads designed for
reactive gases may be installed as “Intrinsically Safe”. Wiring for IS devices is simpler to install and
generally does not require conduit; however, in any case, adequate protection against chafing, crushing or
other hazards should be considered, and an appropriate IS barrier must be installed where the wiring
enters a safe area (see Installation Drawing #GDS-11-0100-EC, Fig. 4-6). For maximum protection against
interference or electrical surge, the GASMAX EC enclosure and any conduit must be properly grounded.
Shielded wire is recommended for all low power signal runs.
Connecting Loop Power / Signal Wiring
To access the GASMAX signal / power connections, remove the cover on the GASMAX EC explosion-proof
enclosure. Loosen the 2 thumbscrews holding the display assembly in place and remove it. oute the
power / signal wires through the conduit entry and connect to green terminal block “TB1” (see Fig. 4-3).
Positive and negative wires are interchangeable. The maximum distance 4-20 mA signals can travel is
dependent upon several factors including the cable gauge, DC power supply voltage level and impedance
of the input of the receiving device. Assuming a nominal 24 VDC power supply, maximum total loop
resistance is approximately 650 ohms.
Figure 4-3: GASMAX EC Loop Power Wiring
S1
ibbon to Display
S1
Display Assembly
Local Toxic Sensor:
Cable from sensor head connects to
S1 on back of display assembly
MounƟng Assembly
CT
EF
SEN
Two-wire 4-20mA Loop

GASMAX EC Operation & Maintenance Manual, Revision 3.5
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Local Smart Sensor
Local toxic sensors are factory installed in a sensor head directly attached to the GASMAX EC enclosure.
Local toxic sensors are always connected to the Smart Sensor connector “S1” located on the back of the
Display Assembly (See Fig.4-4).
Figure 4-4: Local Smart Toxic Sensor
IMPO TANT: TOXIC SENSO S A E SUBJECT TO ACCELE ATED DETE IO ATION IF POWE IS NOT
SUPPLIED WITHIN 3 MONTHS OF SHIPMENT F OM GDS CO P.
S1
ibbon to Display
S1
Display Assembly
Local Toxic Sensor:
Cable from sensor head connects to
S1 on back of display assembly
MounƟng Assembly
CT
EF
SEN
Two-wire 4-20mA Loop

GASMAX EC Operation & Maintenance Manual, Revision 3.5
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Connecting a emote Sensor
GASMAX EC monitors with remote-mount toxic sensors are shipped in two pieces and sensor wiring must
be installed by the end user. emote toxic sensors connect to the Channel 1 Simple Sensor input on the
back of the Display Assembly as shown in Figure 4-6.
Due to the small signal output from toxic sensors, remote direct input toxic sensors should be mounted
no more than 15 wire-feet from the GASMAX EC display. Further, the cable used should be three-wire
stranded with foil shield and should be run inside metallic rigid conduit. GDS Corp recommends Belden
B8771. The cable shield must be connected to an earth ground at ONE END ONLY.
.
Figure 4-5: GASMAX EC Remote Sensor Wiring
TB
USE
-
C
-
A for COMBUSTIBLE, CO2 or PID SEN SO
USE S- -C for OXYGEN or TOXIC GAS SEN SO
S— —C
—C—A
S1
ibbon to Display
S1
Display Assembly
GMII Display Backside “S” to J-box “S”
GMII Display Backside “ ” to J-box “ ”
GMII Display Backside “C” to J-box “C”
S
C
Two-wire 4-20mA Loop

GASMAX EC Operation & Maintenance Manual, Revision 3.5
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Figure 4-6: GASMAX Intrinsically Safe Installation
Initial Setup
Once installed, apply power to the GASMAX EC and verify that the LCD display is active. Certain sensors
may initially indicate off-scale high or low values, but should quickly return to zero if no target gas is
present. During this warm-up delay period, the 4-20mA output is held at 4.0 mA to eliminate false alarms
in any receiving devices. Warm-up delay is one of the user-adjustable parameters (see Section 6).
Once operational, the user should verify the following settings prior to initial calibration:
1. Local time and date: Check date value and adjust time for proper time zone (Sec. 6-5).
2. Tag name or Engineering Units settings: Edit values as necessary (Sec 6-2).
3. CAL SPAN GAS value: Set to match concentration of calibration gas cylinder (Sec 6-2).
PART / DRAWING NO.
SIZE REV.
GDS C orp
2513 Hwy 646
Sa ta Fe, Texas 77510
409 -927-2980
GASMAX EC
I tri sically Safe I s tallatio
3/1/ 13
AGDS-11-0100-EC
1. E tity parameters: Vmax = 30VDC, Imax = 100mA, Ci = 0; Li = 0
2. Barrier may be i Divisio 2 locatio if so approved
3. Cable cap acita ce plus i tri sically safe equipme t capacita ce must be less tha the marked capacita ce (Co ) show o
a y barrier. The same applies for i ducta ce. Capacita ce a d i ducta ce of field wiri g from i tri sically safe equipme t
to the barrier sho uld be calculated as (C
cable
= 60 pF / ft a d L
cable
= 0.2 uH / ft) a d should be i cluded i system calcula-
tio s.
4. Selected barriers must be third party approved as i tri sically safe for the applicatio a d have V
cc
ot exceed i g V
max
a d
I
sc
o exceedi g I
max
of th e i tri sically safe eq uipme t, as show i Table 1.
Table 1:
I.S. Equipme t Barrier
Vmax >= Voc
Imax >= Isc
Ci + Ccable <= Co
Li + Lcable <= Lo
5. Barriers must be i stalled i acco rda ce with barrier ma ufacturer’s co trol d rawi g a d article of the Natio al Electrical
Code ANSI/NFPA 70, CEC Part 1 or other local i stallatio codes, as applicable.
6. Co trol equipme t must ot use o r ge erate more tha 250V with respect to earth
7. I tri sically safe wiri g. Importa t: O ly GASMAX EC two-wire models may be applied as i tri sically safe i stallatio s.
8. The GASMAX EC may be fitted with a y CSA certified compatible XP toxic se sor head . The hazardous locatio i stalla-
tio is limited to a area gover ed by the lowest group rati g of the assembly’s p arts.
9. War i g: Substitutio of compo e ts may impair i tri sic safety.
10. A co duit seal withi 18 i ches of the e closure is ot required for I tri sically Safe i stallatio s.
Barrier Co trol Equipme t
Loop +
Loop -
10-0247
or
10-0247F
Hazardous Area
Class I, Group A, B, C AND D Safe Area
7
7
23456
1910
8

GASMAX EC Operation & Maintenance Manual, Revision 3.5
Page 17
4. CAL MA KE value: Adjust desired output mA during calibration (Sec 6-2).
5. ALA M 1, ALA M 2 settings: Set for desired levels. NOTE: GASMAX EC programmable alarm
levels affect operation of front panel LEDs only (Sec 6-3).
Allow the GASMAX EC to stabilize for at least four hours, preferably overnight if possible. This will allow
the sensor to reach stable equilibrium with respect to environmental conditions such as ambient
temperature, humidity, and barometric pressure as well as applied “reference” and “counter” voltages
generated by the GASMAX EC electronics. At this point, the GASMAX EC can be calibrated and made
operational.

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5CALIB ATION
Calibration Overview
Calibration is critically important to ensure correct operation of the GASMAX EC. The built-in CAL MODE
function is designed to make calibration quick, easy and error free; a successful ZE O and SPAN
calibration requires only four keystrokes. During CAL MODE zero and span, the sensor output is
disconnected and the GASMAX EC transmits a fixed mA value, called the CAL MA KE , to notify the
receiving device that a calibration is in progress. During the following CAL PU GE DELAY time, the
GASMAX EC transmits a fixed 4.0 mA signal to prevent external alarms during calibration. In the case of
local or remote Oxygen sensors, during CAL PU GE DELAY the output simulates a typical atmospheric
reading of 20.8%. CAL MODE automatically exits if no keystrokes are detected after 5 minutes.
Follow these GASMAX EC calibration guidelines:
•Calibration accuracy is only as good as the calibration gas accuracy. GDS Corp calibration gases
are traceable to NIST (National Institute of Standards and Technology).
•Never use calibration gas that has passed its expiration date.
•Check the SPAN GAS VALUE setting and make sure it matches the calibration gas. (See Fig. 6-2)
•Always use a GDS Corp calibration cup that completely surrounds the sensor head.
•Be sure to use ZE O AI , a mixture of 21% oxygen and 79% nitrogen, as a zero reference unless
you are certain that no target gas exists in the area. Ambient gas may result in an ‘elevated zero’
condition that will cause a FAULT to occur once the ambient gas is no longer present.
•Always calibrate a new sensor before depending on the device for personnel or equipment
safety
•Calibrate on a regular schedule. GDS Corp recommends a full calibration every 3 months, with
periodic ‘bump tests’ on a more frequent basis to ensure that the sensor has not been affected
by temperature extremes or the presence of incompatible gases.

GASMAX EC Operation & Maintenance Manual, Revision 3.5
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Calibration Procedure
Before beginning calibration, make sure you have the following items: A cylinder of calibration gas, fixed
flow regulator and an appropriate calibration cup connected to the regulator via a length of flexible
tubing. If necessary, a cylinder of ‘zero air’ may be necessary if the absence of target gas cannot be
confirmed. GDS Corp recommends a flow rate of 0.5 liters / minute for standard gases and a flow rate of
1.0 liters / minute for highly reactive gases such as chlorine or chlorine dioxide.
Figure 5-1: Calibration Setup
To calibrate a GASMAX EC detector:
1. To enter CAL MODE, press the DOWN / CAL key and within 5 seconds press the EDIT key.
2. The screen will display an APPLY ZE O message. Using the setup shown in Fig. 5-1, apply clean
ZE O air unless it can be guaranteed that no target gas is present. After the reading stabilizes,
press the EDIT key to complete the ZE O calibration.
Calibration Cup
Fixed Flow egulator
Cylinder of
Calibration Gas
Flexible Tubing

GASMAX EC Operation & Maintenance Manual, Revision 3.5
Page 20
3. If the ZE O CAL SUCCESSFUL message is displayed, an APPLY SPAN message will appear. Apply
the correct SPAN gas. After the reading is stable, (approximately 1 minute) press the EDIT key to
complete the SPAN GAS calibration. If the SPAN calibration is successful, the display flashes
EMOVE CAL GAS and starts the CAL PU GE delay.
4. Immediately shut off the regulator and remove the calibration cup. At the end of the CAL PU GE
delay, the GASMAX EC output is re-enabled and the unit is fully operational.
The flow chart shown in Figure 5-2 illustrates the above procedure. UP, CAL, NEXT & EDIT labels indicate
keystrokes using the magnetic wand. ZE O or SPAN calibration will fail if the readings exceed built-in
limits for maximum allowable zero or minimum allowable span.
NOTE: A CAL MODE INFO SC EEN IS AVAILABLE TO VIEW CE TAIN CAL MODE PA AMETE S DU ING
CALIB ATION. HOLD THE UP KEY FO 5 SECONDS DU ING CAL MODE TO DISPLAY THIS SC EEN.
Figure 5-2: CALIBRATION FLOWCHART