GDS GASMAX ECx Manual

Operation & Maintenance Manual
GASMAX ECx
Toxic / Oxygen Battery-Powered Gas Monitor with
Smart Sensor Interface
Important: Read and understand contents of this instruction manual
prior to use. Improper use of equipment could result in
instrument malfunction or serious injury.
GDS Corp.
2513 Hwy 646
Santa Fe, Texas 77510
[phone]
[phone] (FAX)
www.gdscorp.com
[email protected]

GASMAX ECx Instruction Manual Revision 1.1
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Table of Contents
SECTION 1 – SAFETY INFORMATION......................................................................................... 3
1.1 Safety Information – Read Before Installation & Applying Power ......................... 3
1.2 Contacting GDS Corp.................................................................................................. 3
SECTION 2 – GENERAL DESCRIPTION ...................................................................................... 4
2.1 Introduction.................................................................................................................. 4
2.2 Description of the Wireless System.......................................................................... 5
2.2.1 RF900 Radio Status (RS) Icons........................................................................... 5
2.2.2 “Radio Awake” Control Timing and Conserving Battery Life......................... 6
2.2.3 GM ECx BATTERY # 10-0293.............................................................................. 6
2.2.4 GM ECx 900MHZ RF MODULE # 10-0291........................................................... 7
SECTION 3 – INSTALLATION INSTRUCTIONS........................................................................... 8
3.1 Ratings and Certifications.......................................................................................... 8
3.2 Sensor Location .......................................................................................................... 8
3.3 Mounting the Enclosure.............................................................................................. 8
3.3.1 10-0322 Magnetic Mount Option......................................................................... 9
3.4 System Design Specifications ................................................................................. 10
3.5 Antenna Transmission Range.................................................................................. 10
3.5.1 Antenna Selection.............................................................................................. 11
3.6 Sensor Installation (with Smart / Simple Sensor Definition)................................. 11
3.7.1 “Sensor Type” and GM ECX Signal Conditioning.......................................... 13
SECTION 4 – INITIAL START-UP................................................................................................ 13
4.1 “Transmitter Configuration” Menu.......................................................................... 13
4.2 Initial Toxic / Oxygen Monitor Start-Up................................................................... 13
4.2.1 Initial Toxic / Oxygen Monitor “Span” Check.................................................. 14
SECTION 5 – OPERATING INSTRUCTIONS.............................................................................. 14
5.1 CAL MODE - Routine Sensor Calibrations.............................................................. 14
5.2 ALARM OPERATION................................................................................................. 16
5.2.1 ALARM 3 – UNDERSTANDING FAULT / LEVEL OPERATION ....................... 16
SECTION 6 – SETUP MENU CONFIGURATION ........................................................................ 17
6.1 Menus Database Configuration ............................................................................... 17
6.2 Configuration Using the Magnetic Wand:............................................................... 17
6.3 System Configuration Menus: ................................................................................. 18
6.4 Alarm Settings:.......................................................................................................... 19
6.5 Sensor Information: .................................................................................................. 20
6.6 Clock / Warm-Up & Cal Purge Delays SETUP: ....................................................... 20
6.7 COMMUNICATIONS SETUP: .................................................................................... 21
6.7.1 GM ECx AND C1 BASE STATIONS: ................................................................. 22
6.8 SYSTEM SECURITY: ................................................................................................. 22
6.9 LCD Contrast Adjustment: ....................................................................................... 23
SECTION 7 – TECHNICIANS ONLY MENUS.............................................................................. 23
7.1 Introduction: .............................................................................................................. 23
7.2 Set Gain to Unity (Technicians only!): .................................................................... 24
7.3 PreAmp Gain Adjust (Technicians only!): .............................................................. 24
7.4 Simple Sensor Input Type (Technicians only!):..................................................... 24
7.5 Zero Cal Value (Technicians only!): ........................................................................ 25
7.6 Raw Min / Max Counts (Technicians only!): ........................................................... 25

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SECTION 1 – SAFETY INFORMATION
1.1 Safety Information – Read Before Installation & Applying Power
IMPORTANT
Users should have a detailed understanding of GM ECx operating and maintenance instructions.
Use the GM ECx only as specified in this manual or detection of gases and the resulting
protection provided may be impaired. Read the following WARNINGS prior to use.
WARNINGS
•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.
•Do not paint the sensor assembly or transmitter.
•Do not use the GM ECx 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
operation.
•Use only a sensor assembly compatible with the GM ECx.
•Periodically test for correct operation of the system’s alarm events by exposing the
monitor to a targeted gas concentration above the High Alarm setpoint.
•Do not expose the GM ECx to electrical shock or continuous severe mechanical shock.
•Protect the GM ECx from dripping liquids and high power sprays.
•Use only for applications described within this manual.
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.
1.2 Contacting GDS Corp.
GDS Corp technical support is available between the hours of 7:30am and 5:00pm Monday
through Thursday and 7:30am until Noon on Friday Central Standard Time. Please call 409-927-
2980 or FAX [phone]. Our email address is inf[email protected] and our website is
www.gdscorp.com. Our shipping address is 2513 Hwy 646, Santa Fe, TX 77510.

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SECTION 2 – GENERAL DESCRIPTION
2.1 Introduction
IMPORTANT: This manual describes only GM ECx toxic / oxygen gas monitor equipped with
internal RF wireless modem and RF900 firmware. This battery powered device has no external
power or signal wiring and is limited to self powered electrochemical sensors for toxic and oxygen
measurements. A separate manual is available for the GASMAX IIx, an externally powered
wireless monitor for bridge-type sensors. Both are single channel fixed-point monitors designed to
provide continuous monitoring of hazardous gases in the workplace. Gas values are graphically
displayed in engineering units in either bar-graph or 30-minute trend formats (Figure 2-1).
Flashing front panel LED’s help notify personnel when alarm levels have been reached. Only
periodic calibration checks are needed to assure dependable performance.
The GM ECx provides a license free 900MHZ wireless link to any GDS Corp C1 Protector
Controller or C2 Quad Protector controller (when configured with an RF900 wireless modem). Up
to 16 GM ECX wireless monitors may communicate to one C1 Controller.
Advanced microcontroller electronics and superior graphic LCD operator interface offers
enhanced diagnostics and fault analysis not possible in competing products. Non-volatile
memory retains all configuration data during power interruptions. The magnetic keypad allows
non-intrusive calibrations to be easily performed by one person without opening the enclosure. A
standard “real time clock & calendar” feature allows event logging of calibrations and alarm trips
for review on the LCD readout.
Compatible sensors include an 8-wire Smart Sensor interface capable of configuration data
uploads to the monitor as well as traditional Simple sensors with three-wire interface. A separate
PC compatible USB Interface device (part # 10-0252) allows Smart sensors to be preloaded with
configuration variables via a PC; when connected, the GM ECx gives the user the option to
upload this data to the GM ECx. This configuration data includes alarm set points, range, target
gas, calibration constants and other variables required to match the GM ECX to a specific
application. For Simple sensors with no smart interface, the USB device allows direct GM ECx
configuration from a PC or a six channel GM ECX Educator device.
Additional features include:
•On screen radio status icons indicate “Server In Range”, “Server Out of Range” and “Low
Battery” conditions.
•No potentiometer or jumper settings required. All setup is done with menus accessed via the
LCD / magnetic keypad operator interface without opening the enclosure.
•Field adjustable alarm levels flash front panel LED indicators for HIGH, WARN, FAIL
conditions. Relays are not available with this low power model.
•CAL MODE advises when to apply gas during calibrations.
•A thirty-minute trend screen shows rate of change of gas exposures.
•Sensor life bar-graph updates after each SPAN calibration.
•Modular design affords efficient installation and plug in sensors allow changing target gases
after installation.
•New smart sensors are recognized by the GM ECx and prompts users to either upload new
configuration data or continue with data from the previous smart sensor.
•Sensors are industry proven for fast response and long life.

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Figure 2-1: Data Displays
2.2 Description of the Wireless System
All GDS Corp wireless transceivers utilize a FHSS (Frequency Hopping Spread Spectrum)
Server-Client network where multiple Clients synchronize their frequency hopping to a single
Server. The Server transmits a beacon at the beginning of every frequency hop (50 times per
second). Client transceivers listen for this beacon and upon receiving it synchronize their
hopping with the Server.
Each GM ECx wireless “broadcast” includes a 10-bit monitored gas value, battery voltage
indication and a status byte. When equipped with optional radio modems, C1 Protector and C2
Quad Protector Controllers are capable of functioning as Clients or Servers. Multiple GDS Corp
controllers may receive transmissions from the same GM ECx gas monitor, but only one
controller per wireless network may be configured as the Server.
Each transceiver on a wireless network must have its RADIO SETUP menus configured to share
the same Hop Channel (0-32) and System ID (0-255) to communicate (see section 6.7). There
should never be two servers with the same Hop Channel / System ID settings in the same
coverage area. The Server must be in a powered location and should be centrally located since
all Clients must receive the server’s beacon in order to communicate.
Correct planning and design of wireless systems are imperative for ensuring a successful
installation. It is highly recommended that a site drawing indicating location of monitors and base
station, line of site obstructions, and sources of RF interference be submitted when requesting a
quotation.
2.2.1 RF900 Radio Status (RS) Icons
Figure 2-1 shows the GM ECx data display and identifies the “radio status” (RS) icon which
appears on the LCD screen upper left corner. Status conditions indicated by the RS icon are
Zzz’s (sleep mode), Server In Range (server beacon received), Server Out of Range (server
beacon not received) and Low Battery. Low Battery conditions also flash the FAIL led.
It is important to understand RS icons only update as the TXD LED flashes indicating an RF
transmission has occurred. RF transmissions typically occur on 5-minute intervals, but increase
to six-second intervals during alarm conditions.

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2.2.2 “Radio Awake” Control Timing and Conserving Battery Life
Most GM ECx battery power is consumed as the radio communicates to the wireless network.
Each communications cycle consists of the following sequence: Wake the radio in receive mode;
listen for the Server’s beacon; synchronize to the Server’s hopping frequency; transmit data
packet, return to sleep mode. This sequence takes between 0.25 to 1 second to complete.
Transmit power levels are adjustable; lower power setting will result i longer the battery life.
Every six seconds, the monitor performs a “sniff test” to detect level of target gas present at the
sensor. At each “sniff test”, the Zzz’s RS icon is briefly replaced by “Server In Range” or “Server
Out of Range” icon and the readout is updated to indicate the current gas value. The radio
remains in sleep mode if the gas value does not trip either the A1 or A2 alarm. Upon each 50th
consecutive “sniff test” (every 5-minutes) the radio wakes up, receives the Server’s beacon, and
transmits the latest gas data. These 5-minute transmissions ensure that all controllers can
monitor the wireless communications link even when no alarms exist. If A1 or A2 alarms do exist
during the “sniff test”, the radio wakes, receives the Server’s beacon, and transmits its data
immediately.
The following list identifies each of the conditions that cause the radio to transmit:
•Five minutes, or fifty sequential reads (when there is no A1 or A2 alarm). Any receiving
controller will report a “Communications Error” if the GM ECx does not reply for periods of
greater than 18-minutes. A3 and FAIL alarms do not increase radio transmission rates.
•Every six seconds, if there is an A1 or A2 level alarm.
•Upon entry into CAL mode a value of 75 (-15.6% scale) is transmitted. Controllers so
programmed will indicate “IN CAL” when this occurs.
•Upon entry into CAL PURGE mode a value of 200 (0% scale) is transmitted.
NOTE: Oxygen sensors transmit a value of 20.9% upon entry into CAL PURGE mode.
•Holding the magnet over the UP key for >10seconds forces a transmission of the current
reading value.
2.2.3 GM ECx BATTERY # 10-0293
GM ECx electronics consists of the lower 10-0299/Battery I/O PCB (Figure 2-2) connected by a
cable to the upper Display assembly with 10-0291 RF Module PCB (Figure 2-3). The 10-0293
3.6 volt lithium ‘D’ cell battery will continuously power the unit for up to one year and may be
replaced by following the procedure in Figure 2-2.
Power switch (SW1), on the 10-0299 Battery PCB, applies battery power to the GM ECx monitor.
SW1 should be OFF if the monitor is to be out of service for long periods.
IMPORTANT: Do not turn SW1 ON until the controller designated as Server is fully operational
and ready to communicate to the GM ECx. Battery life is reduced if the GM ECx is on for long
periods while unable to communicate to the Server controller.
IMPORTANT: DO NOT ATTEMPT TO CHARGE THIS BATTERY OR REPLACE WITH ANY
OTHER THAN PART #10-0293 FROM GDS CORP.

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Figure 2-2: 10-0299/Battery I/O PCB
2.2.4 GM ECx 900MHZ RF MODULE # 10-0291
The 10-0291 RF module mounts “piggy back” to the back of the Display assembly as shown in
Figure 2-3. The MMCX RF connector connects to the antenna fitting’s pigtail coax cable. There
is also a slender 4 conductor cable between the 10-0291 and the 10-0299 battery I/O PCB bolted
to the bottom of the enclosure.

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SECTION 3 – INSTALLATION INSTRUCTIONS
3.1 Ratings and Certifications
The enclosure is NRTL certified for Division 1 hazardous area installations for explosion-proof
Class 1 Groups B,C,D (see Figure 3-1). The GM ECx is designed to meet ISA 92.0.01 Part 1 for
Toxic Monitors. The 10-0295 antenna fitting has an RP-SMA connector and is suitable for
Division 2 classified areas. An optional 1000-2193 antenna is also available for Division 1
classified areas. Figure 3-3 shows both antenna styles.
3.2 Sensor Location
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 centimeters) above the potential gas leak and heavier than air gases should be
this distance below. Even though the GM ECx is designed for rugged service, sensors should be
protected from environmental damage from water, snow, shock, vibration and dirt.
3.3 Mounting the Enclosure
The GM ECx standard enclosure is a cast aluminum explosion-proof (NEMA 7) enclosure. The
GM ECx antenna should typically be mounted with “line of sight” access to the controller’s base
station antenna. If a good “line of sight” angle is not possible the GM ECx will usually still function
properly at ranges up to 1500 feet but obstructions should be kept to a minimum.
WARNING: Qualified personnel should perform the installation according to applicable electrical
codes, regulations and safety standards. Ensure correct cabling and sealing fitting practices are
implemented. Install the GM ECx to a wall or bracket using the predrilled mounting flanges with
I.D. 0.25 on 5.0 inch centers (Figure 3-1).
CAUTION: The sensor head should never be installed pointing upwards.

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Figure 3-1: GM ECx Explosion-Proof Housing
Modular design simplifies the installation of the GM ECx (Figure 3-2). A top Display Assembly is
mounted with captive thumbscrews and is easily removed to access internal components. The
RF900 module mounts piggyback to the back of the Display Assembly. Wiring from toxic or
oxygen sensors terminates at the10-0232 Display Assembly. This Display Assembly is the only
PC board supplied with the toxic / oxygen GM ECx. The enclosure is equipped with two threaded
3/4 inch NPT conduit fitting outlet and pre-drilled mounting flanges.
WARNING: Qualified personnel should perform the installation according to applicable electrical
codes, regulations and safety standards. Insure correct cabling and sealing fitting practices are
implemented. Do not aim the sensor pointing upward. Install the GM ECx to a wall or bracket
using the predrilled mounting flanges with I.D. 0.25 on 5.5 inch centers (Figure 3-1). If conduit is
rigid and able to support the weight of the GM ECX, the mounting bolts may be omitted.
CAUTION: The sensor should never be installed pointing upwards.
3.3.1 10-0322 Magnetic Mount Option
GDS Corp offers a magnetic mount for the GM ECx instrument enclosure. The 10-0322Magnetic
Mount securely attaches the assembly to any solid steel structures that is at least 6 inches wide.
Figure 3-2: Outline Drawing

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3.4 System Design Specifications
Power Supply: Integral non-rechargeable 3.6 volt 19AH lithium D cell battery. Replacement part
# 10-0293.
Power Consumption: <2mA during “sleep” mode, 40mA during “receive beacon” mode, up to 1
amp during 1 watt “transmit” mode. Transmit power may be set from 10mW to 1 watt (see
Section 6-7)
Transmit (TX) Power: 30dBm at highest 1W power setting. Transmit power may be set from
10mW to 1 watt (see Section 6-7)
Receive (RX) Sensitivity: -100 dBm
Radio Frequency: Hopping occurs between 902 – 928MHZ.
Memory: Non-volatile E2memory retains configuration values in the event of power outages.
3.5 Antenna Transmission Range
The distance radio signals can travel is dependent upon several factors including antenna design,
transmitter power and free space losses. In order for a wireless link to work, the available system
operating margin (TX power - RX Sensitivity + Antenna gains) must exceed the free space loss
and all other losses in the system. For best RF line-of-site, the combined height of both antennas
must exceed the Fresnel zone diameter (see below).
Dist. between ant's Fresnel zone diameter Freespace loss (dB)
1000 ft (300 m) 16 ft (4.9 m) 81
1 Mile (1.6 km) 32 ft (9.7 m) 96
5 miles (8 km) 68 ft (20.7 m) 110
10 miles (16 km) 95 ft (29 m) 116
Example:
The RF900 radio modem has the following parameters:
•Maximum RF900 TX power setting = 30 dBm (1 Watt)
•RF900 RX sensitivity = -100 dBm (this is a constant)
•Antenna gain (standard equipped dipole) = 2.1dBi x 2 = 4.2dBi
So the system operating margin at ten miles is 30 + 2.1 -116 + 2.1 + 100 = 18.2 dBm. This
margin should be enough to transmit 10 miles if free space was the only loss in the system. For
this to be the case, however, the antennas must be mounted with a combined height greater than
95ft above all obstructions. In practice however, there are many losses in the system besides just
free space and it is recommended there be at least 20dB to 40dB system operating margin.
RF “Rules of Thumb”
•Doubling the range with good RF “Line of Sight” (LOS) increases the free space loss by
at least 6 dB.
•Doubling the range without good RF LOS increases the free space loss by at least 12 dB.

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3.5.1 Antenna Selection
GDS Corp offers locally mounted dipole antennas suitable for either Division 1 or Division 2
classified areas as shown in Figure 3-3 below. Antennas may also be remotely mounted if it is
necessary to raise the height to achieve better RF L.O.S. (Line of Sight).
Figure 3-3: Local Antennas for Hazardous Locations
3.6 Sensor Installation (with Smart / Simple Sensor Definition)
Sensors used with the 10-0247 sensor head (see Figure 3-5) are considered “smart” since they
include a memory device that uploads sensor information to the GM ECx anytime a new sensor is
installed. The GM ECx may also accommodate other industry standard “simple” electrochemical
toxic / oxygen sensors, without the memory device, by accepting their wiring into TB2 of the 10-
0232 Display Assembly (see Figure 3-4). The 10-0247’s Smart Sensor cable connects to S1 of
the 10-0232 Display Assembly (see Figure 3-4). This unique Smart Sensor Interface may be
used to configure smart sensors and / or GM ECX’s from a PC rather than entering all variables
via the magnetic keypad.
Sensors used with the smart sensor head (see Figure 3-5) are considered “smart” since they
include a memory device that uploads sensor information to the GM ECx anytime a new sensor is
installed. The GM ECx may also accommodate other industry standard “simple” electrochemical
toxic / oxygen sensors, without the memory device, by accepting their wiring into TB2 of the
Display Assembly (see Figure 3-4). Sensor heads with the 8-wire Smart Sensor cable connects
to S2 of the 10-0291 Radio Assembly (see Figure 3-4). This unique Smart Sensor Interface
may be used to configure smart sensors and / or GM ECx from a PC rather than entering all
variables via the magnetic keypad.

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Figure 3-4: 10-0232 Display Connections (RF900 module removed for clarity)
Figure 3-5: 10-0247 Smart Sensor Head Assembly
Smart Sensors are automatically recognized by the GM ECX. The Smart Sensor identification
screen in Figure 3-6 is shown after power-up, upon installation of a new smart sensor or by
viewing INPUT type in the SENSOR SETTINGS / INFO menu (section 5-5).
SMART SENSOR
Type: Cat-Bead
Span: 100
Zero: 0
SN: xxxxxx
Born On: 01/28/04
Last Cal: 04/05/04
ANY key to Exit
ERROR CODE 01
Incorrect Sensor
installed. Install
correct sensor or
update transmitter.
SEE MANUAL
EDIT key to update.
Any other to abort.
If installed sensor
type does not match
transmitter database
Figure 3-6: Smart Sensor Info / ERROR Screens

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3.7.1 “Sensor Type” and GM ECX Signal Conditioning
Electrochemical sensors are available for detection of many different gas compounds and ranges.
The GM ECx must be configured for each type’s different response coefficients, signal strength
and gain and offset requirements. The block / wiring diagram in Figure 3-7 illustrates how the GM
ECx is able to accept many sensor types without the need of manual potentiometers or jumpers.
Smart Sensors carry this setup information with each sensor.
Figure 3-7: GM ECX Block / Wiring Diagram
SECTION 4 – INITIAL START-UP
4.1 “Transmitter Configuration” Menu
Figure 4-1shows the GM ECX XMITTER CONFIG menu used to activate channels, precisely
calibrate 4-20mA outputs and set time / date. Its menus are set at the factory and typically not
needed by the user. To access from any data display, press and hold the NEXT key for 5-
seconds until the screen appears requesting a special key sequence (4-UP keystrokes).
Figure 4-1: Transmitter Configuration Menu
4.2 Initial Toxic / Oxygen Monitor Start-Up
GM ECX Toxic / Oxygen Monitors, factory equipped with a local Simple or Smart electrochemical
sensor, rarely require adjustments (other than routine calibrations) to provide accurate readings.
However, after installation the following checks should be performed to insure proper operation.

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In addition, alarm levels, Measurement Name ASCII fields and other variables may require
attention by users in order to best serve their application.
4.2.1 Initial Toxic / Oxygen Monitor “Span” Check
Prior to the initial Routine Sensor Calibration described in section 5.1, a coarse SPAN gas
reading verification should be performed after installation. Apply an upscale gas value of at least
25% of full scale to the sensor. For example, if 0-100ppm H2S is the measurement range, apply
at least 25ppm but not more than 100ppm. The indicated value should read within 15% of full
scale. Remember, this is only a coarse check and precision calibrations are performed in
Routine Sensor Calibrations described in the following section 5.1. Section 7.4 describes
PREAMP GAIN adjustments that may be required if full-scale ranges are changed.
SECTION 5 – OPERATING INSTRUCTIONS
5.1 CAL MODE - Routine Sensor Calibration
Calibration is the most important function for insuring correct gas readings at the GM ECx. The
CAL MODE (flow chart shown in Figure 5-2) is designed to make calibration quick, easy and error
free. A successful ZERO and SPAN calibration requires only four keystrokes. The wireless 10-
bit output indicates CAL MODE by transmitting 75 counts. It then transmits 200 counts during the
subsequent CAL PURGE delay to prevent external alarms during calibration. CAL MODE
automatically exits if no keystrokes are detected after 5 minutes.
The GM ECx wireless 10-bit output range is 200 to 1000 counts for 0 to 100% of full scale. The
GM ECx indicates CAL MODE by transmitting 75 counts (-15.6% FS) to receivers on the network.
Toxic gas ranges transmits 200 counts (0% FS) during the subsequent CAL PURGE delay to
prevent external alarms during calibration. NOTE: To prevent activating A1 & A2 low trip alarms
at the controller, oxygen ranges transmit 884 counts (20.9% oxygen reading) upon entry into CAL
PURGE. CAL MODE automatically exits if no keystrokes are detected after 5 minutes.
Follow these GM ECX calibration guidelines:
•Calibration accuracy is only as good as the calibration gas accuracy. GDS Corp
recommends calibration gases with NIST (National Institute of Standards and
Technology) traceable accuracy to increase the validity of the calibration.
•Do not use a gas cylinder beyond its expiration date.
•Calibrate a new sensor before use.
•Allow the sensor to stabilize before starting calibration (approximately 5 minutes).
•Calibrate on a regular schedule. (GDS Corp recommends once every 3 months,
depending on use and sensor exposure to poisons and contaminants.)
•Calibrate only in a clean atmosphere, which is free of background gas.

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Figure 5-1: Calibration Gas Input
Use the following step-by-step procedure to perform ZERO and SPAN calibrations.
1. To enter the CAL MODE from either data display, press the DOWN / CAL key and within
5 seconds press the EDIT key.
2. Using the Cal-Cup, apply a clean ZERO gas or be sure there is no background target gas
in the monitored area. After the reading is stable, (approximately 1 minute) press the
EDIT key to perform a ZERO calibration.
3. If the ZERO calibration is successful, press the NEXT key to proceed to the SPAN check.
4. Apply the correct SPAN gas at .5 liters/min. After the reading is stable, (approximately 1
minute) press the EDIT key to perform a SPAN calibration.
WARNING: The SPAN gas used must match the value specified since this is what the
GM ECX will indicate after a successful SPAN calibration. The Cal Span Value may be
edited if it becomes necessary to apply a different gas concentration (see Cal Span
Value in section 3.4).
5. If the SPAN calibration is successful, the display flashes “REMOVE CAL GAS” and starts
the CAL PURGE delay (see section 6.6).
6. CAL MODE will be complete after the end of the CAL PURGE delay.
The flow chart in Figure 5-2 illustrates the above procedure. UP, CAL, NEXT & EDIT labels
indicate keystrokes using the magnetic wand. The CAL MODE information screen (top of the
chart) is available for advanced users to see Offset / Gain calibration constants and live analog to
digital converter (A/D) counts. Span Gas calibration values may also be edited from this screen.
Holding the UP key, for 5 seconds during CAL MODE, displays this screen.

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Calibration history records are logged and may be viewed in the Sensor Information menu (see
section 6-5).
REMOVE
CAL GAS
NEXT KEY
REPEAT CAL
SPAN FAIL
NEXT
SPAN CAL
Successful
EDIT
live reading/eunits
EDIT to Set ZERO
NEXT=SPAN CA L Mode
Apply ZVAL
Eunits
REPEAT CAL
ZERO FAIL ZERO CAL
Successful
(If ZERO Cal OK)(If ZERO Cal Fails) EDIT (If SPAN Cal OK)(If SPAN Cal Fails)
ERROR CODE 4
show for 5 seconds show for 5 seconds
Hold UP key 5 sec. Hold UP key 5 sec.
Offset = xxxx
Gain = xxxx
Counts = xxxxxx
live reading/Eunits
EDIT=Set Span Value
Cal Span Value=xxxxxx
DATA DISPLAY
CAL, then EDIT
NEXT = Return to Cal
live reading/eunits
EDIT to Set ZERO
NEXT=EXIT CAL Mode
Eunits
Apply SVAL
Sensor Life
Back to DATA
DISPLAY
ERROR CODE 5
CAL MODE info screen
(use to change SPAN GAS value
and to see Offset / Gain constants)
Measurement Name
% LEL
2
Measurement Name
% LEL
0
PGA = xxxx%
Figure 5-2: Cal-Mode Flow Chart and Menus
5.2 ALARM OPERATION
GM ECX’s have front panel LED indicators for Alarm 1, Alarm 2 and FAIL.
CAUTION: GM ECX Alarm LED indicators function even without the presence of the 10-0234
Relay option. With battery power operation, to conserve power, alarm LED’s only flash during
alarm events.
5.2.1 ALARM 3 – UNDERSTANDING FAULT / LEVEL OPERATION
The “A3” alarm is typically dedicated to FAULT conditions indicating sensor failures or “out of
measurement range” conditions. However, some applications require a third level alarm. The A3
menu is identical to A1 & A2 and may be set to trip at an upscale level value. A3 WILL ALSO
TRIP WITH MISSING OR FAILED SENSORS REGARDLESS OF THE LEVEL VALUE!
CAUTION: Missing or failed sensors always flash the Alarm 3 led. This is true even with A3
configured as a level alarm and users should be aware that A3 level alarm events might be
caused by the monitored level, or, by a missing or failed sensor.

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SECTION 6 – SETUP MENU CONFIGURATION
6.1 Menus Database Configuration
All GM ECX configuration variables are stored in its menu database. Many menu items will
contain default values from the factory and require changes to better match a user’s particular
application. GM ECx menus may be configured from the magnetic keypad in 5-10 minutes per
transmitter. For installations consisting of many points, an interface device is offered to allow
Smart sensors, GM ECx’s or GM ECx Educators to be configured from a PC’s USB port. This is
useful when GM ECx’s are not yet installed or if a portable computer may be carried to each unit.
The Educator allows configuring up to six GM ECx’s at the PC and transporting their configuration
data to each location. This is useful when numerous installed units must be configured.
The GM ECx’s configuration menus are shown in Figure 6-1.
Figure 6-1: Configuration Menu Tree
6.2 Configuration Using the Magnetic Wand:
Passing the magnetic wand past the EDIT key, from either data display, displays EC INPUT
PAGE 1 setup screen as shown in Figure 6-2. The UP / DOWN keys maneuver the pointer while
EDIT enters sub-levels of menu items. All SETUP menu items have at least one page of sub-
menus. Items with sub-menus are indicated by the > symbol (right hand pointing arrow) at the
end of each line. Edit menu items by pointing to them, press the EDIT key to display the cursor,
press UP / DOWN to change that character, press NEXT to move the cursor, then press EDIT

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again to load the new item and remove the cursor. Press NEXT to reverse out of the sub-menu.
To view EC INPUT PAGE 2, press the DOWN key with the pointer aimed at the bottom item on
PAGE 1.
Figure 6-2: Setup Menu Entry
6.3 System Configuration Menus:
The System Config. group consists of two pages of menus as shown in Figure 6-3. Each menu item’s
description follows in this section.
Figure 6-3: System Config. Menus
User Info may be edited to contain virtually any 16-character ASCII field. It is typically used to
describe the monitored point by user tag # or other familiar terminology.
Eunits (engineering units) may have up to a 10 character ASCII field. Many common gases have
pre-configured Eunits based upon the sensor type and each may be edited in this menu as
described in Configuration Using the Magnetic Wand section 5-2.
Zero (0%) defines the reading to be displayed when 4mA (0%) is the GM ECX output.
Span (100%) defines the reading to be displayed when 20mA (100%) is the GM ECX output.
The highest reading allowed is 9999 includes negative polarity sign and one decimal point.
Polarity is only indicated for negative readings.
Decimal Points sets the resolution of the LCD readings and may be for 0, 1 or 2. Example:
ZERO readings for 0, 1 & 2 DP’s respectively are 0, 0.0 & 0.00.
Cal Span Value sets what upscale value must be applied when performing Span calibrations.
Readout Deadband allows forcing low values to continue to read zero. This is useful when there
are small amounts of background gases that cause fluctuating readouts above zero. The highest
amount of deadband allowed is 5%.
Track Negative,set to NO, causes negative values to read the Zero (0%) value in data displays.
The CAL MODE readout displays negative values regardless of this setting and negative values
below the Fault set point will still cause the Fault alarm to trip. The gas value’s 200-1000 counts
output always locks at 200 counts when the reading is negative.
Backup Config. allows users to store the entire current GM ECX menu database into non-
volatile memory for restoration later if incorrect values are accidentally entered or uploaded.

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Restore Config. restores the GM ECX menu database to the values from the most recent
Backup Config. This menu item is only available if a smart sensor is not installed. The special
keystroke sequence of 4 consecutive UP keys is also required to perform backup and restore
operations.
Upload Sensor Data allows manually uploading the entire smart sensor database to the GM
ECX from the smart sensor. This menu item only appears if a smart sensor is connected.
6.4 Alarm Settings:
The Alarm Settings page has the Alarm 1, 2, 3 Setups and Event Log submenus shown in
Figure 6-4. Alarm 1, Alarm 2 and Alarm 3/Fail menus are identical and therefore described only
once in this section. Alarm conditions are indicated by A1, A2, A3 LCD icons and by flashing the
A1, A2 and FAIL led’s.
Figure 6-4: Alarm Settings Menus
Set Point enters the engineering unit value where the alarm trips. It may be negative and trip
when monitored values fall out of range in this direction. A3 has a default negative 5% of range
Set Point with Low Trip set for YES. This makes it function as a FAULT alarm and trip when the
monitored value is more than 5% “out of range”.
Dead-Band has a minimum value of 1% and a maximum value of 10%. It is useful for preventing
alarm cycling when the monitored value is hovering around the set point. EXAMPLE: With a
range of 0-100 ppm, if Dead-Band equals 5% and the set point is 20 ppm, after tripping at 20 ppm
the value must drop below 15 ppm to reset.
ON Delay allows entering a maximum 10 second delay before this alarm becomes active. This is
useful for preventing nuisance alarms caused by brief spikes beyond the set point.
OFF Delay allows entering a maximum 120 minute delay before clearing an alarm after the alarm
condition is gone. This is useful for continuing an alarm function, such as operation of an exhaust
fan, for a period of time after the alarm condition clears.
Low Trip set to YES causes the alarm to trip as the value falls below the set point.
Latching set to YES causes the alarm to remain active even after the condition is gone and only
reset when the UP / RESET key is pressed from a data display.

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6.5 Sensor Information:
Sensor Information has the SENSOR SETUP/INFO menus shown in Figure 6-5
SENSOR SETTINGS/INFO
Install Sensor
Recall Cal History
Input Type SMART
New Sensor 01/28/04
Recent Cal 04/05/04
>
>
INSTALL NEW SENSOR
EDIT to install
New Sensor.
Any other key
to Exit.
CALIBRATION DATES
Record 22 of 22
CAL Date: 04/05/04
UP/DOWN to scroll
NEXT to EXIT.
INSTALL NEW SENSOR
Historical CAL data
Will be Deleted.
EDIT to Accept
NEXT to Abort
EDIT
EDIT
Sensor Life
>
SMART SENSOR
Type: Cat-Bead
Span: 100
Zero: 0
SN: xxxxxx
Born On: 01/28/04
Last Cal: 04/05/04
ANY key to Exit
Figure 6-5: Sensor Information Menus
Install New Sensor should always be performed when a new simple sensor is installed. This
deletes historical CAL data and sets sensor life to 100% after initial calibration of the new simple
sensor. The GM ECX Smart sensor interface will automatically detect new smart sensors and
this menu is therefore not available with a smart sensor connected.
Recall Cal History recalls each successful calibration. These dates may be reviewed by
scrolling with the UP / DOWN keys.
Input Type indicates what kind of input or sensor the GM ECX is configured to accept and is
typically pre-configured at the factory. There are three Input Type possibilities consisting of
simple EC negative, simple EC positive and Smart. Smart sensors upload sensor type and other
data to the GM ECX and may be viewed on the SMART SENSOR information screen.
New Sensor displays the date when a new sensor was last installed.
Recent Cal displays the most recent calibration date.
6.6 Clock / Warm-Up & Cal Purge Delays SETUP:
Since the GM ECX is equipped with a Real Time Clock & Calendar Time and Date must be set to
correctly match its location. They are set at the factory in a 24 hour format but may require
adjustment to match the location’s time & date after shipment. Follow the procedure in
Configuration Using the Magnetic Wand in section 6.2.
Warm Up and Cal Purge time delays are also available to prevent unwanted alarm trips. Figure
6-6 shows the menu for these items.