WatchGas GDS404+ Multi Channel Combustible and Toxic Gas Monitor User Manual

WatchGas GDS404+ Multi Channel Combustible and Toxic Gas Monitor

ADVISORY
Note: 404/404+ setup – page 11 controller set up, page 12 alarm board.

SYSTEM DATA – EQUIPMENT OWNER USE

Fault Relay: Normally Energised – Latched
Alarm Relays: Normally De–Energised – Latched
Details:

Description

The WatchGas 404+ is a multi channel combustible and toxic gas monitor, which can accommodate up to 4 sensor channels housed in wall mounting enclosure. Sensors may be added or removed as required, but should be carried out with the power to the unit switched off. Each sensor continuously monitors for gas, the display will show the gas type being monitored, the current gas reading and the location of the sensors.
The gas alarms are activated at preset levels and will remain on until the gas clears, these in turn activate the appropriate alarm relays. The fault indicator is initiated should the sensor connecting lines become open/short circuit, or an electronic fault be detected.
The control unit requires an a.c. mains power supply and/or a low voltage d.c. power supply. When both are provided the low voltage d.c. acts as a standby supply in the event of an a.c. mains power failure.

• MAINS ON LAMP (P) GREEN indicates that power is being supplied to the control unit.
  When the optional standby battery is fitted loss of mains supply will result in the GREEN Mains ON Lamp changing to RED.

• GAS ALARM will be indicated by a red LED and display channel changing to a red background with text indicationg the alarm status. Fault conditions are indicated by amber displays.

• SOUNDER initiated in the presence of a fault or gas alarm condition.

• TEST when pressed for 15 seconds alarm indicactions are activated. If pressed for a further 15 seconds alarm relays will change state.

• RESET used to mute the sounder and reset alarms, gas alarms cannot be reset until the gas concentration has decreased below the set alarm level.

• ALARM RELAY INHIBIT Pressing the reset pad for 15 seconds will inhibit the alarm relays which is indicated by the inhibit LED coming on. To remove the inhibit press the reset pad for 15 seconds, the fault light will turn off.

• ZERO POTENTIOMETER meter zero adjust when the sensor is monitoring a gas free atmosphere.

• SPAN POTENTIOMETER used to adjust the meter indication to read correctly when the sensor is subject to a test gas of known concentration.

• ALARM SET SWITCH alarm trip points setting.

• SENSOR CURRENT POTENTIOMETER sensor supply adjustment

Technical Specification

NUMBER OF CHANNELS
ONE, TWO, THREE OR FOUR CHANNELS OUTPUTS
Common Relays – user selectable

• Low Alarm RL1 – D.P.C.O. normally energised or de–energised– default set ND
• Latched or Unlatched – default set latched
• High Alarm RL2 – D.P.C.O normally energised or de–energised– default set ND
• Latched or Unlatched – default set latched
• Third Alarm RL4 – D.P.C.O. normally energised or de–energised– default set ND
• Latched or Unlatched – default set latched
• Fault Alarm RL3 – S.P.C.O normally energised or de–energised– default set ND
• Global Alarm Relay RL5 – S.P.C.O. changes on all alarms and is resettable at all times
• Inhibit Indicator – RL6 – S.P.C.O contacts 1A@24v DC

Channel Relays

• High and Low Alarm relays S.P.C.O. normally energised or de–energised– default set ND
• Latched or Unlatched – default set latched
• All contacts rated 3A/230v AC

SENSOR CABLE
Flammable (catalytic) – 3 core, 1.5mm screened cable, mineral insulated copper sheathed or steel wire armoured – maximum cable loop resistance 20 ohms. Toxic/Oxygen – 3 core 0.5 mm screened cable, mineral insulated copper sheathed or steel wire armoured – maximum cable loop resistance 200 ohms.

POWER SUPPLY
230, 110v, AC 50/60Hz. or 24v DC (21–30 volts tolerance)

ADD ON OPTIONS:
Standby battery 1 hour – Field installation – position the batteries so that they are supported by the battery locating bracket and then retained using the tywrap, connect the battery connectors to terminal blocks JP11 and JP12

Installation

The WatchGas 404+ Series control instrumentation is designed for installation in a safe area only. Siting of the instrument should be chosen with regard to the following points:

• Cable within the enclosure should be cut back to the minimum length and having been terminated should be kept away from electronic components and the ribbon cable. Cable requiring to pass from the bottom of the enclosure to the top should be run down the right hand side adjacent to the enclosure metalwork.
• Away from sources of local heat and with room for adequate ventilation.
• Within easy reach and audible distance of operating personnel.
• Convenient to a separately fused power supply.
• Incoming sensor cables and outgoing alarm annunciation.
• Sensor cables to be electrically shielded i.e. M.I.C.C., steel wire armoured, screened cable. To prevent any effect from earth currents the cable shielding should be grounded at one end only. The instrumentation should be subjected to a minimum of vibration and shock. Ascertain the voltage rating of the power supply to which the instrument will be connected

SITING THE SENSING HEADS
A key feature of the installation is the correct siting of the sensing head. Several considerations must be taken into account, the most important being the density of the gas.

Density (air = 1)

Acetone| 2.0| n–Hexane| 3.0
Ammonia| 0.6| Hydrogen| 0.1
Benzene| 2.8| Methane| 0.6
n–Butane| 2.0| n–Octane| 3.9
Carbon monoxide| 1.0| n–Pentane| 2.5
Ethane| 1.0| n–Propane| 1.6
Ethyl alcohol| 1.6| Town gas| 0.4–0.7
n–Heptane| 3.5| Xylene| 3.7

Under still air conditions, a ‘lighter than air’ gas such as methane leaking from a small orifice at ground level, will ris in a plume the shape of which approximates an inverted cone. As the gas rises, it draws air from the surroundings and creates a turbulence. Resulting from this there occurs rapid dilution and, unless a sensor is positioned within the plume, there will be no initial indication of a leak.
As gas continues to escape, the diluted concentration rises to ceiling level and begins to layer. In time the concentration at ceiling level will increase and this, in turn, will displace air downwards.
Dangerous levels will, therefore, tend to occur at ceiling level and the thickness of this layer will increase with the passage of time. Ventilation of the room will of course alter the situation significantly but it should be remembered that if the ventilator s not at ceiling level, a dangerous concentration can still occur between the top of the ventilator and the ceiling.
For heavier than air gases such as propane or butane, the formation of dangerous layers occurs at ground level. These gases tend to behave like water and will run down gradients and pool at the lowest point.
The number of heads required in individual rooms is determined by the number of possible hazards in the vicinity. Gas leakage may occur around valves, flanges and anywhere where gas pipes are jointed. It may be possible to cove several probable gas leaks in one room by the careful siting of a single head. Cable ducts, trenches and manholes are also likely places where a build up of heavy gases may collect.
When siting a head in such places it is most important to ensure that there is no likelihood of flooding by wate , or excessive dust which may block the sintered disc and prevent gas reaching the sensor.
When monitoring gases outside, those lighter than air will be quickly dispersed, but gases heavier than air will tend to form in layers and again cause a dangerous hazard. When siting heads outside prevailing winds must be taken into consideration and adequate protection given against wind and rain.

POISONING OF CATALYTIC SENSORS
Catalytic elements used in flammable gas sensors are liable to be rendered inactive due to ‘poisoning’ by certain groups of compounds. In general contact with any gaseous compound capable of producing an involatile residue upon heating is to be avoided.

Examples of such substances are:

1. Silicon containing vapours, as emitted by silicone polishes, greases and
2. Petroleum vapours containing tetra–ethyl lead or other organo–metallic
3. Phosphorus in the form of phosphate

These compounds will permanently affect the detector and if their presence is suspected the response of the detector should be determined by the calibration procedure. It is also possible that the reaction of the detector to a flammable gas could be inhibited by halogen containing gases such as chloroform, carbon tetra chloride and trichloro–ethylene. this effect is not permanent.

Commissioning

Before applying power to the instrument ensure that all detector heads are connected to the sensor terminals on the printed circuit board (fig 2) and that each detector head is connected to its appropriate channel:

WARNING – DO NOT INSERT OR REMOVE ALARM CARDS FROM THE MOTHERBOARD WHILE THE POWER IS ON

Switch on power to the instrument. Check that the green power lamp is on.

Each channel alarm card has a green (ACTIVE) indicator located on the mother board (D102, D202, D302, D402).

On power up these will flash for 60 seconds indicating that the sensors are stabilisin , during this period all alarms are held in the off condition.

Where an internal standby battery has been supplied the connectors should be made on JP11 and JP12. Re–set alarms by pressing the reset button located on the front panel.

Allow ten minutes for the sensors to stabilise.Any flammable or toxic sensors should be adjusted to read zero by means of appropriate ZERO POTENTIOMETER marked (Z) on the alarm module, or for oxygen sensor adjust the s–span potentiometer for a reading of 20.8 repeat for Channel 2, 3 and 4.

CALIBRATION

Establish calibration figures with respect to the L.E.L. limit or the T.L.V. limit of the calibration gas being used. See page 10. The following calibration gases are recommended:

• Flammable gases – 2.5% methane in air. Toxic gases – T.L.V. When using this gas ensure adequate ventilation.
• If necessary zero each detector channel in clean air (for ambient oxygen monitoring the meter should be adjusted to read 20.8% using the s–span potentiometer – disconnect one sensor lead to adjust zero.
• Apply the calibration gas to the appropriate head at a flow rate of approximately 1 litre per minute
• When the meter reads a steady value adjust the Span Potentiometer marked (S) to obtain the correct reading for the calibration gas being used.

SERVICE ADJUSTMENTS
The following adjustments need only be made if the standard factory settings (see test certificate) are to be adjusted.

CALIBRATION WHEN USING 4~20MA SENSOR TRANSMITTERS
Where a sensor transmitter has been supplied the setting up procedure as described on pages 14 to 22 should be followed.
NOTE: Where a transmitter is used, adjustment of the alarm module calibration potentiometer is not required (factory set for 4~20mA input signals), gas calibration need only be carried out at the detector head end.

ALARM LEVEL ADJUSTMENT (LO/HI)

1. Alarm levels may be adjusted as follows: – For toxic/flammable gases zero the instrument in clean air using the zero potentiometer (for ambient oxyge monitoring the meter should be adjusted to read 20.8 using the s–span potentiometer).

2. Press the alarm set switch for approximately 2 seconds the sounder will bleep and the low alarm indicator will come on, the green power indicator will turn off, release the alarm

3. Using the zero potentiometer adjust the digital display for the required low trip level reading, press the alarm set switch until the high alarm indicator comes on, release the alarm set

4. Adjust the digital display to read the required high trip level reading and again press the alarm set switch both alarm indicators will come

5. Zero the digital display (toxic/flammable) or 8 for oxygen and press alarm set switch, alarm indicators will tur off and the green power indicator will turn on.

THIRD ALARM (AL3) SET UP PROCEDURE
The screen displays all required information simultaneously as well as the sensor’s name/location with a maximum of 16 characters.
The third alarm (AL3) is set using the potentiometer on the front panel PCB labelled RL4. This is a global alarm that applies to all four channels. One sensor zero level should be raised up to the desired alarm level by turning that channel’s zero pot. The Alarm 3 set pot should then be turned until the third alarm just activates default setting (80~100 FSD). The zero pot can then be adjusted back to normal setting (see page10).
There are jumpers for setting the third alarm level relay to be normally energised/de–energised (jumper fitted for normally energised) and the alarm being latched/unlatched (jumper fitted for latched).

DISPLAY TEXT CHANGES
Gas type and units (8 characters), decimal places and sensor name/location are set up using a PC via a micro USB to USB lead using WatchGas terminal or hyperterminal software.
Connect the front panel to a PC using a micro USB lead, this should auto–detect and appear as a com port, the number of which can be found in windows ‘device manager’ ports for example. The terminal program should be set up using the same method and settings as the WatchGas combi panel (baud rate 2400).
The terminal window will appear as below. Follow the onscreen instructions:

Press the character on the left of the list of commands to change that specific settin . The sensor name has 16 available characters and the gas type has 8

SENSOR SUPPLY ADJUSTMENT (CATALYTIC SENSOR)

Factory set – no further adjustment required unless a change of sensor type is being made.
For ease of setting, measurements are taken across a 1ohm resistor (located on each sensor board) which is connected in series with the supply to the detector head. Current required by each type of sensor is (VQ21–300mA/ VQ23 DCP–335mA) therefore, measuring mV across the 1 ohm resistor at test point TP1 or TP2 (on the mother board) and sv test point on each sensor board, will provide a mV reading proportional to mA’s supplied, adjustment may be carried out using the sensor volts adjustment potentiometer.
Alternatively the sensor voltage may be set at the detector head across terminals P and W (VQ21 2v/VQ23 DCP 2.5v) and again use the sensor volts adjust potentiometer.

4–20MA OUTPUT ADJUSTMENT
Adjustments: With the load connected to the appropriate 4~20–mA output terminal (typically 100 ohms) and a digital volt meter connected to the test pins TP3 + TP4 – ensure that the sensor is in clean air, and that the instrument is reading zero.
Adjust the 4mA potentiometer to read 4mV on the digital voltmeter.
Using the appropriate sensor zero potentiometer adjust the alarm panel digital display for full scale reading. Adjust the 20mA output potentiometer until the digital voltmeter reads 20mV
Return the alarm panel digital display reading to zero by readjusting the zero potentiometer.

Service – routine attention

The owner or occupier of the premises should place the supervision of the system in the charge of a responsible executive whose duty it should be to ensure the day to day operation of the system and to lay down the procedure for dealing with a gas alarm or fault warning. To ensure reliability an agreement should be negotiated for regular servicing. When a service contract cannot be arranged an employee with suitable experience of electrical equipment should be trained to deal with the more simple servicing and instructed not to attempt to exceed the scope of such training.
Liaison should be established with those responsible for maintenance of the building fabric or redecoration etc. to ensure that their work does not cause a fault or otherwise interfere with the operation of the gas alarm installation. Particular attention appertaining to the Detector Head.
The operating instructions should be kept available preferably with the control unit, all faults, service tests and routine attention given should be recorded.
DAILY: A check should be made that any fault condition which may be indicated is in fact being attended to and that all other indicators are normal.
WEEKLY: In plants involving a high risk process or having gases which may cause loss of sensitivity a check on calibration should be carried out.

TWICE YEARLY MAINTENANCE SCHEDULE

1. All zeros at the control unit to be checked, logged and
2. Each detector to be gas tested and reading logged (sensitivity checked).
3. Field indicators to be
4. All alarm set points checked and re–aligned.
5. Lamp
6. All faulty parts replaced where
7. All filter elements checked and replaced as necessar .
8. Power supply – complete functional
9. Visual inspection made to confirm that all cabling fitting and equipment is secure, undamaged and adequate protected.

FAULT DIAGNOSIS

Unable to zero meter

1. Sensor open circuit
2. Sensor leads incorrectly connected
3. Alarm card not positioned correctly

No front panel indication – Check ribbon cable is connected correctly

ACTION TO BE TAKEN IF THE APPARATUS ALARM SOUNDS:

• A Extinguish all naked flames, including all smoking materials B Turn off all gas appliances.
• Do not switch on or off any electrical lights or
• Turn off the gas supply at the gas emergency control and/or (with P.G supply) the storage tank. E Open doors and windows to increase ventilation

If the alarm continues to operate, even after an alarm re–setting action where appropriate, and the cause of the leak is not apparent and/or cannot be corrected, vacate the premises and immediately notify the gas supplier and/or the gas emergency 24 hour service in order that the installation may be tested and made safe and any necessary repair carried out.

Table of lower explosive limits – L.E.L.
The figures quoted below are taken from British Standards Institute publication BS EN 60079–20– 1:2010 and show the L.E.L. of some of the more common gases and vapours:

Table of occupational exposure limits – P.P.M.
The figures quoted below are taken from guidance note EH40 from the Health and Safety Executive and ACGIH

INDICATORS

• L.E.L. – Lower Explosive Limit
• PPM – Parts Per Million
• % vol. – % Volume
• Hi – High Alarm (Red)
• Lo – Low Alarm (Red)
• C1–C4 – Channel (Sensor)
  • Fault Indicator (Amber)
  • Power On (Green)
  • Mains Fail (Red)
  • Inhibit (Amber)
• Reset – Sounder/Alarms
• Test – Electronic System Test

Display Board

RELAY SELECTION
Common Third Alarm Relay – Normally energised/Normally de -energised – (J2)

Mother Board

RELAY SELECTION

• Common High Relay – Normally energised/Normally de–energised – (J3)
• Common Low Relay – Normally energised/Normally de–energised – (J1)
• Global Alarm Relay – Normally de–energised
• Common Fault Relay – Normally energised/Normally de–energised – (J5)
• Inhibit Relay – Normally de–energised
• Channel relays (1–4) A/B (Lo/Hi) see alarm board page 14

SOUNDER PERMANENT MUTE
JP10 remove

STANDBY BATTERY
Connect leads to – (JP11 and JP12)

CONTROLLER SELECTION
For operation as 404 JP17 should be fitted For operation as 404+ JP17 should be removed (JP17 located below sounder)

Alarm Board (plugin)

RELAY SELECTION

• Channel Relay A – Low/High Alarm – Lo/Hi – Factory set – Low for A+B
• Channel Relay B – Low/High Alarm – Lo/Hi – Factory set – High
• Normally energised or de–energised – E/D – Factory set – De–energised (D)

AUTOMATIC OR MANUAL RESET – A/M
Oxygen Monitoring (factory set) – O2 Oxygen Alarm Set Low/Low Alarm – LL Time delay to alarm – T1 – 10 secs T2 – 30 secs When used with WatchGas 300 Flow sample systems – FS

SENSOR SELECTION
24v (4/20mA input) P – Pellistor (mV input)

4~20MA OUTPUT
TP3/TP4

CALIBRATION
TP1/TP2

ADJUSTMENTS

ALARM BOARD SELECTION

For operation as 404 JP1 should be fitted and J15 should be set to 40 For operation as 404+ JP1 should be removed and J15 should be set to 404+ (J15 located above SN block, J1 located below U4 (large IC)

• RED ident R = flammabl
• YELLOW ident Y = toxic
• BLUE ident B = oxygen
• GREEN ident G = others

CV TRANSMITTER

FLAMMABLE

TECHNICAL

• Gas Type – Flammable Gases

• Input Voltage – 12~30vDC – 24v nominal

• Current – Nominal 160mA

• Output Standard
  Analogue 4~20mA (250 ohms max) – 3 wire (source mode – standard)
  Option 1~5v output – Link – LK1

• Sensor Cable
  3 core 1.5mm screened, maximum cable loop resistance 20ohms

• Alarm Relay Relay contacts S.P.C.O. rated 1A/24vDC RL2 3A/230vAC RL1

• Options (safe area board only)
  Fire Alarm panel signalling – Remove LK1
  Logic output – JP1 position L and end of line link JP2 – normally set at A (analogue)

• Full Board Options – On board sounder

Installation

For hazardous area equipment see specific instructions supplied with the equipment, or visit our website for technical information. Siting of the equipment should be chosen with regard to the following points:

1. Away from sources of heat and with room for adequate air circulation.
2. Within easy reach for operating and maintenance
3. Connecting cables to be electrically shielded, i.e. M.I.C.C., steel wire armoured, screened cable or steel
4. For sensor location see our

Note: Sensor cables should not be run in the same ducting as power cables.

Set Up

1. Having powered up allow 5 minutes for the sensor to
2. The sensor current/voltage should be set by connecting a voltmeter (mV range) across TP3/TP4 and adjusting the sensor voltage potentiometer (10 turn) until the required voltage reading is obtained (mV meter reading = mA sensor current) caution – do not exceed 360mV (mA). See sensor cell supply
3. Zero the card in clean air by adjustment of the potentiometer marked zero until the green ON/Zero LED just turns from GREEN/ RED to (At this point the output will = 4mA). If you require to check this, connect a digital meter (mV range) to the test pins marked TP1 and TP2, if adjustment is required adjust the 4mA potentiometer (4mV = 4mA).
4. Where a digital panel meter is fitted to the CV card the reading ma be adjusted by the DPM Z potentiometer (zero).

Calibration
With the digital meter connected to the test pins TP1 and TP2 and a reading of (4mV clean air) apply test gas and wait until a maximum reading is obtained, if necessary adjust the 20mA potentiometer for the required mV reading for the calibration gas being used.
Where 4 ~ 20mA span = 0 ~ 100% L.E.L. (Lower explosive level) and the sensor is to be calibrated for Methane which has an L.E.L. of 5% vol, when using 1% Methane in air test gas (20% L.E.L.) a reading of 7.2mv (7.2mA) would be required.
Where a Digital panel meter is fitted the display may be adjusted by using the DPM S potentiometer (span).

Additional Relay Board Alarm Trip Point Adjustment
This level will normally be set at 20% of the range reading i.e. 7.2mA.

1. Connect the DVM as above, using the zero potentiometer adjust for the required trip level (mv)
2. Adjust the alarm level potentiometer until the relay just changes state.
3. Using the zero potentiometer re–adjust the DVM to

The above adjustment may be carried out in house by connecting the CV transmitter directly to a DC power supply.

Sensor Cell Supply Table

CV TRANSMITTER TOXIC/OXYGEN

Technical

Installation

For hazardous area equipment see specific instructions supplied with the equipment, or visit our website for technical information. Siting of the equipment should be chosen with regard to the following points:

1. Away from sources of heat and with room for adequate air
2. Within easy reach for operating and maintenance
3. Connecting cables to be electrically shielded, i.e. M.I.C.C., steel wire armoured, screened cable or steel
4. For sensor location see our a

Note: Sensor cables should not be run in the same ducting as power cables.

Calibration

1. Connect a digital voltmeter (miIIivolt range) to the + and – test terminals (2 wire system) or X and Y test terminals (3 wire system). For 3 wire systems the CV is preset in the current source
2. In clean air check that the DVM reads 4mV, if not adjust the 4mA potentiometer on the CV transmitter
3. Apply test gas and wait until a maximum DVM reading is obtained, if necessary adjust the 20mA potentiometer for the required mV reading for the calibration gas used (see range/reading on test certificate or printed on the CV circuit board)
4. For oxygen level monitoring remove the sensor terminal connector from the PCB J4 or yellow wire and adjust the 4mA potentiometer for 4mA (4mV).
5. Where a digital panel meter is fitted to the CV card the reading may be adjusted by the DPM Zero potentiometer

Reconnect the cell and allow reading to stabilise adjust the DVM reading for 17.3mA (20.8% ambient oxygen) using the 20mA potentiometer. Where a Digital panel meter is fitted the display may be adjusted by using the DPM S potentiometer (span).

Additional Relay Board Alarm Trip Poi nt Adjustment
This level will normally be set at 20% of the range reading i.e. 7.2mA.

1. Connect the DVM as above, using the 4mA potentiometer adjust for the required trip
2. Adjust the alarm level potentiometer until the alarm LED just comes on.
3. Using the 4mA potentiometer re–adjust the DVM to

The above adjustment may be carried out in house by connecting the CV transmitter directly to a DC power supply. Should a full board be required to operate on a 2 wire loop then the relay must be disabled – remove JP2

Gas Type Programming – Works/preset

• CO, H2S, SO2, NH3, H2
  remove R4, R6, R10, R15, R28, R29,

• HCN
  remove R4, R6, R8, R10, R15, R28, R29,
  NO2, CL2 O3,
  remove R4, R7, R10, R11, R28, R29

• NO, HCL, C2H4O
  remove R3, R4, R6, R10, R12, R15, R28, R29,

• O2
  remove R3, R8, R6, R15, R42, R43, IC–U2

Set up procedure

New sensors are supplied ready to connect to the system. The following procedure is for full set up and where the sensor cell has been replaced – only sections 5, 6, 7, 9 and 11 need to be carried out. Voltage measurements are made wrt AG unless otherwise specified.

1. Insert jumpers J20 and J6 position SO for 4–20mA source output.

2. Turn sensor voltage potentiometer anti-clockwise (minimum voltage).

3. Connect sensor to J2 terminal W–white Y–yellow P–pink.

4. Connect 24V + and 0V to JP10, short the 4~20mA terminal by inserting test link at

5. Measure the sensor voltage at SV and adjust by turning sensor volts pot for the correct
   DO NOT EXCEED THE REQUIRED VOLTAGE OTHERWISE PERMANENT DAMAGE WILL OCCUR.
   See sensor cell supply table.

6. Rotate 20mA pot fully anti-clockwise (minimum )

7. When in clean air the sensor bridge is zeroed by adjusting zero pot until the dual colour LED D1 is

8. Connect PC hyper terminal using RS232 Combi adaptor (part no. 160–510 and lead part no. 160–515) at 4800 baud connected to Ensure jumper J29 is fitted befor programming and initialise the sensor using (C) calibration mode, then shift + ($) command from the keyboard.

9. Using a digital mV meter measure across test pins TP8/9 and adjust 4mA pot for 4mA (zero) = 4mV

10. Then press (Z) on the PC to zero the reading

11. Apply a known test gas to the sensor (56% LEL = 2.5% vol methane) for 1 minute at a flow rate of 1 litre to give 13mA = 13mV across test pins TP8/9, adjust 20mA pot for correct mV reading.

12. When using a PC press (S) to enter span mode and using (H) or (L) adjust the reading to 56% LEL.

13. Press (space) to exit span and then (X) to exit the calibration mode
    

14. Connect the sensor to a Combi alarm panel and ensure that it reports in correctly.
    Note:– Fit the end of line (EOL) link J1 if the sensor is to be installed at the end of the sensor cable.

15. If front panel display board is fitted via connector J5 an U12 adjust contrast for LCD contrast.

16. Remove J9 test link for normal operation.

17. Insert link J12 to enable the bridge fault detection. (4–20mA output falls to 2mA in fault).

18. Ensure J29 address link is removed (this is only used when changing address from a Panel).

Using magnets (set up)

The Combi sensors which have an LCD display fitted also incorporate 3 reed switches which can be activated using external magnets through the glass window of the flameproof XDIwin enclosure. These magnets do not act instantly and have to be in close proximity to L, M and R on the front display for   a few seconds to activate a software setup function.
The left magnet enters the Auto zero  ON  or  OFF  menu.  This allows small drift changes in the sensor to be compensated for but is not operational when the sensor readings are greater than 5% of full scale. Therefore auto zero is inactive when a larger gas reading is present. When the remove magnets message appears, move the left magnet away and then the display shows if auto zero is ON or OFF. The left magnet puts auto zero ON and the right magnet turns it OFF. With no magnets present, the display will return to normal after a few seconds timeout.
The right magnet allows the CAN address of the sensor to be changed. When the ADDRESS menu is displayed with a prompt to remove the magnet, and then the display shows the address and that the right magnet decreases it whilst the left magnet will increase it. This is then stored in internal nonvolatile memory and the display will automatically revert to normal operation.
The centre magnet is used to inhibit the sensor. As with the left and right magnet functions the display requests that you remove the magnet and then the state of the inhibit appears on the LCD. The left magnet then puts the sensor into inhibit whilst the right magnet removes it. An amber LED on the front panel under the LCD flashes when the sensor is inhibited. When all magnets are removed, the display will revert to normal operation.
The left and right magnets together allow the calibration menu to be used

Removing both magnets as instructed on the LCD presents the first part of this multi menu which is ZERO. With no gas present use the left magnet to increase the reading and the right magnet to decrease to achieve a zero reading on the display. A timer  is displayed on the LCD and when this reaches 0, the next menu is displayed. This timer is 15 seconds approximately and is reset back each time a magnet is near. Waiting till timeout  is acceptable but this timeout can be speeded up by placing a magnet near to the centre position.
SPAN is the next part of the menu and gas should be applied to the sensor at this time.
The left magnet increases the gain and the right magnet reduces gain. The actual sensor value can be seen on the display to rise or fall respectively.

LOW ALARM is the next menu and left and right magnets increase and decrease this value.
HIGH ALARM is next followed by OVER RANGE alarm.
The direction of the alarms is displayed as ^ for rising and v for falling but these can be changed using left and right magnets together.
Sensor cell supply table

Set up procedure: 204D2C Issue Tv3

NEW UNITS ARE SUPPLIED READY TO CONNECT TO A SYSTEM. THE FOLLOWING PROCEDURE MAY NEED TO BE CARRIED OUT FOLLOWING CHANGES TO THE SYSTEM:

1. Insert J8 jumper to receive signal from external 4~20mA source (Fig.3)
2. Connect external 4~20mA source to the 4~20mA input terminal (J11) on the right hand side of the board.
3. Connect terminal J10 as shown in Fig.2
4. Connect DVM (mV range) across TP7 + TP15 to measure current supplied by 4~20mA device (mV = mA)
5. Ensure that the CAN LED is ON and flashing occasionall .
6. Connect RS232 pod to connector J3 and to a PC running HyperTerminal at 4800 baud.
7. The HyperTerminal display shows a continuous data output and allows input from the PC keyboard.
   • Press C to enter calibration mode
   • Press shift $ to initialise the memory if new PCB (defaults to Flam %LEL)
   • Press G to change gas/signal to the type required for the cell/unit in use. (NOTE: When using a ‘user gas’ press ‘E’ to edit name after using ‘G’ to select. Also make sure to select a vacant user gas number, 61–68, as the addressable sensor will overwrite data entered at the Combi panel.
   • The range of the gas/signal selected will have a default setting which can be changed by pressing ‘R’
   • Press A and enter CAN address of this sensor
   • Press N to toggle the number of decimal places between 1 and 2 (i.e. dp=1 or dp=2)
   • Press B to toggle the deadband ON and OFF
   • Press F to toggle the external fault option ON or OFF (only available when external source has local fault indication)
   • With input signal reading 4mA press Z to zero the reading.
   • Press S to span the reading. Apply gas/signal from external source and press H or L to adjust the reading.
   • Press space to exit the span.
   • Press X to exit the calibration mode.
8. Connect to a combi panel and ensure that the sensor reports in correctly.
   Note: that if this sensor is at the end of the communication wires then it will need terminating by inserting jumper J1(EOL). The continuous data output when connected to HyperTerminal is the same format as for the Flammable sensor. The software used is identical.

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