Yes, but the multicore cable must have an overall screen (shield) and the multicore cable must not be used to connect any device other than monicon gas detectors.

The following table indicates the maximum inductance and capacitance values for a T100 cable, fitted with an approved IS barrier, in a hazardous area.

The cable used to connect a CGS500 sensor should be 3-core cable, with stranded copper conductors and an overall screen (shield). The gauge of cable should be selected to ensure that the cable resistance does not exceed the maximum specified for the controller. The maximum cable resistance for the Multichannel controller is 10 Ohms per line (i.e. 20 Ohms Loop). The following table will give an indication of maximum cable runs for the Multichannel controller.

The maximum cable resistance for the Single Channel and Four Channel controllers is 4 Ohms per line (i.e. 8 Ohms Loop). The following table will give an indication of maximum cable runs for the Single Channel and Four Channel controllers.

Cable capacitance is the electrical capacitance of a cable. A length of cable will exhibit the characteristics of a capacitor. To further assist the understanding of cable capacitance, a definition of electrical capacitance may help: “In electricity, capacitance is the capability of a body, system, circuit, or device for storing electric charge. Capacitance is expressed as the ratio of stored charge in coulombs to the impressed potential difference in volts. The resulting unit of capacitance is the Farad. In an electric or electronic circuit a device designed to store charge is called a capacitor”.

Cable inductance is the electrical inductance of a cable. A length of cable will exhibit the characteristics of an inductor. To further assist the understanding of cable inductance, a basic definition of electrical inductance may help: “In electricity inductance is the quantity that measures the electromagnetic induction of an electric circuit component. The self-inductance, L, of a circuit component determines the magnitude of the electromagnetic force (emf) induced in it as a result of a given rate of change of the current through the component. Similarly, the mutual inductance of two components, one in each of two separate but closely located circuits, determines the emf that each may induce in the other for a given current change. Inductance is expressed in Henrys”.

Cable resistance is the electrical resistance of a cable. A length of cable will exhibit the characteristics of a resistor. To further assist the understanding of cable resistance, a basic definition of electrical resistance may help:

“Electrical Resistance is the property of an electric conductor by which it opposes a flow of electricity and dissipates electrical energy away from the circuit, usually as heat. Higher resistance is provided by a conductor that is long, small in cross section, and of a material that conducts poorly. Electrical resistance is measured in Ohms. The phenomenon of resistance arises from the interactions of electrons with ions in the conductor”

The screen of the cable should normally be connected to 0V, ONLY at the controller and NOT at the detector. However, if the detector is mounted on a non-conductive surface, then the detector enclosure should be earthed locally OR through the cable screen. It is essential that electrical current does NOT flow in the detector cable screen as may happen if the screen was earthed at both ends.

Tools required:
A: Calibration tool, P/N: 010-001
B: 50% LEL combustible gas in cylinder with flow regulator
C: Flow adapter, P/N: C13055

1. Ensure that the system has been allowed to stabilise for 24 hours
2. Momentarily operate the CAL switch (The display will flash)
3. Ensure that the detector in clean air (i.e. no combustible gas present)
4. Check that the VALUE display reads 0
5. If the VALUE display does not read 0, adjust the ZERO potentiometer
6. Set flow rate to 300mL/minute on regulator and apply gas to sensor
7. Observe the reading on the VALUE display until the reading stabilises
8. Adjust the SPAN potentiometer until the VALUE display indicates 50
9. Remove the flow adapter from the sensor
10. Observe the reading on the VALUE display until the reading stabilises
11. Adjust the ZERO potentiometer until the VALUE display reads 0
12. Repeat steps 6 to 11 if necessary
13. Momentarily press the CAL switch to return to normal mode
14. Refer to the Instruction Manual for further calibration details

A simple calibration check may be performed by proceeding with steps 1, 2, 3, 4, 6, 7 and 10 to check that the system indicates the correct gas concentration within the prescribed tolerance levels

We recommend that the CGS500 sensors should be calibrated 3-4 weeks after installation and at least every six months thereafter. In harsh environments or where there may be poisons present, calibration should be more frequent. For further information on calibration, please contact your local Monicon Distributor.

We recommend that the IR100 sensors should be calibrated at least every year. The IR100 has no “consummable” parts or chemicals so routine calibration will usually involve a simple calibration check to ensure that the pump and the electronics are functioning correctly. For further information on calibration, please contact your local Monicon Distributor.

We recommend that the T100 sensors should be calibrated at least every six months. In harsh environments or where there may be aggressive chemicals or solvents present, calibration should be more frequent. For further information on calibration, please contact your local Monicon Distributor.

Calibration with the correct target gas is the most accurate method to calibrate the sensor. However, if this is not possible, then cross calibration using an alternative gas is a less accurate alternative method. Cross sensitivity figures for the CGS500 sensors are listed in the Cross Sensitivity section.

We recommend that the CGS500 sensors should be calibrated using a constant flow rate 300mL/minute. Lower flow rates may result in inaccurate results while higher flow rates will waste calibration gas and may result in errors caused by windage effects.

We recommend that the CGS500 sensors should be calibrated using mixture of 50%LEL of the calibration gas in air.

Synthetic air is a mixture of approximately 21% oxygen and 79% nitrogen. When there is a possibility that there is a combustible gas or vapour present, synthetic air may be used to calibrate the zero point of the CGS500 sensor.

We recommend that the CGS500 sensors should be allow to stabilise for 24 hours prior to calibration for optimum accuracy. However, where this is not possible, with reduced accuracy, these sensors may be calibrated after just one hour to stabilise.

The C13055 flow adapter is fitted with barbed tube fittings designed to accomodate 4mm ID (inside diameter) and 6mm OD (outside diameter) tubing. The tube may be nylon, rubber, PTFE or other suitable tubing.

An “open collector” output is the collector terminal of a transistor available for the connection of external loads. On Monicon’s controllers the polarity of the open collector outputs is NPN and the load may be connected between the output and the positive (+) supply. The maximum voltage is the DC supply voltage of the instrument (i.e. 12Vdc or 24Vdc) and the maximum current is 100mA.

The Single Channel and Four Channel controllers have an IP (Ingress Protection) rating of IP65. Briefly, this means that the enclosure is dust-tight and protected against water jets.

Yes, but we do not recommend this when using thermocatalytic sensors. Overrange latching has been incorporated to comply with the requirements of European Norm EN50057 and British Standard BS6020. It should be noted that if Overrange latching is disabled, the controller will not be in compliance with the requirements of EN50057 and BS6020.

Yes. All Monicon controllers feature a special “Calibration Mode”. In Calibration Mode, the relays are inhibited and will not activate, even if gas is applied to the sensor.

While we recommend the use of genuine Monicon gas sensors and gas detectors, Monicon’s controllers have been designed to accomodate a wide range of detectors and sensors from many manufacturers.

Monicon’s mains powered controllers have a battery backup facility. The controllers are fitted as standard with the necessary circuitry to trickle charge backup batteries. The controllers also have the necessary circuitry to sense mains failure and automatically switch over to the backup battery without interrupting operation. The batteries are not supplied but are available as optional extras. We recommend a 12V/1.2AH sealed lead-acid battery for the Single channel and 4 Channel controllers. The Multichannel system required 24Vdc and we recommend two 12V/6AH batteries connected in series.

Yes. The parameters you have selected in Setup Mode are stored in non-volatile memory (EEPROM) when you press the CAL button to exit CAL mode. These values are retained even in the event of a total power failure.

Momentarily press the CAL button. Then press the SET button to scroll through the parameters that you can alter. Pressing the up or down arrows will alter these parameters. Momentarily pressing the CAL button again will store the changes you have made. Persons who are not familiar with Gas Monitors may, in the process of familiarising themselves with the controller, inadvertently change the settings and be unable to operate the instrument. A facility has been incorporated to allow the novice to restore the factory default settings easily. Pressing the SET button until the STATUS display indicates “FD” will offer the user the option to restore the unit to the Factory default settings. Pressing the up arrow will restore the Factory Default settings. Pressing the CAL button will save these settings.

It is possible to fit up to 16 control modules and one facilities module in a standard 19″ rack.

Yes. The default scan rate is approximately 3 seconds and this is suitable for most applications. However, the Scan Rate is user programmable from System Setup mode. Press the CAL button and the STATUS display will indicate CA. Press the SET button until the STATUS display indicates CS for “Channel Scan”. The VALUE display will indicate the current scan time in 100mS intervals. Press the up or down arrow buttons until the STATUS display indicates the required value. Press the CAL button to save the new value. Futher details on changing the scan rate are available in section 3 of the instruction manual.

Yes. The Multichannel controller is also available in the American “4U” format.

Yes. All Monicon controllers feature a PCB mounted “Metal Oxide Varistor”. This device is capable of absorbing and safely dissipating unwanted surge energy up to 7 Joules.

This should be determined by reference to the TLV, STEL or LEL value of the substance being monitored. For combustible gases in the range 0-100% of the Lower Explosive Limit (LEL), it is recommended that Alarm 1 be set to 25%LEL, Alarm 2 to 50%LEL and Alarm 3 to 75%LEL. For toxic gases, refer to the TLV or STEL of the gas being monitored. However, we do not recommend that alarm setpoints be adjusted below 10% of full scale or above 90% of full scale. Ultimately, the alarm setpoints should be selected by the safety officer responsible for the gas being monitored.

Configuring for Enrichment alarms means that if the gas concentration goes above the setpoint the alarm activates while configuring for Deficiency alarms means that if the gas concentration goes below the setpoint the alarm activates. For monitoring most gases, typically Enrichment alarms are selected. However, for monitoring oxygen levels, it is usual to select Deficiency alarms for at least one alarm.

Latching alarms means that if the alarm activates and subsequently the gas condition returns to normal, the alarm will remain latched until the RESET button is pressed. Non-Latching alarms reset automatically. Each alarm can be selected as latching or non-latching in Setup Mode. Please refer to the instruction manual for further details.

Normally Energised means that the relay is in its energised state when not in alarm and becomes de-energised when in alarm. Normally De-energised means that the relay is in its de-energised state when not in alarm and becomes energised in alarm. Normally Energised relays are “fail-to-safe” as the relay will changeover even in the event of a total power failure. Normally energised relays consume more power than normally de-energised relays.

Our 4 channel controller is compatible with our T100 detector and CGS500 sensors. Also any other device which carries a 4-20 mAmp output.

Fully Independant Operation means that there is no inter-dependance between channels. Each channel module has all the electronics necessary for it to be fully autonomous with its own power converter, microcontroller, display, relays, analogue output and fault detection. Fully Independant Operation means that in the unlikely event of a channel failing, it will not affect the operation of another channel.

“SPDT” means “Single Pole Double Throw”. This means that the relay has a set of “change-over” contacts. SPDT relays have three terminals. The “C” terminal is Common, the NC terminal is Normally Closed and the “NO” terminal is Normally Open.

An analogue output is a current signal generated by a controller to signal data to an external device such as a chart recorder or a PLC. Monicon’s controllers generate an industry standard 4-20mA current signal. 4mA represents zero gas concentration. 20mA represents full-scale gas concentration. Current signals lower than 4mA represent abnormal conditions such as calibration mode or fault.

Monicon’s controllers use a technology known as “Digital Signal Processing” (DSP) to reduce the incidence of false alarms caused by spurious or unwanted signals from the sensor or the detector. While the technology behind DSP is rather complex, it can be explained in simple terms as follows: DSP is a technique where the signal from the sensor is analysed by the the controller’s on-board computer over a period of approximately 3 seconds. The on-board computer takes several hundred samples of the sensor signal over this time period and through a series of mathematical algorhythms and formulas can determine if the sensor signal indicates a gas concentration or if the sensor signal indicates, for example a humidity change, radio frequency interference, electromagnetic interference, vibration, etc.

The Single Channel and Four Channel controller enclosures are manufactured from ABS (Acrylonitrile Butadiene Styrene) resin. ABS is an attractive, yet rugged copolymer that affords great protection to the internal electronics. ABS has been chosen as the most appropriate material because it can withstand most harsh industrial, chemical and marine environments and does not exhibit the effects of corrosion that can attack most metallic materials.

The latest release of all Monicon’s controllers feature relay ratings of 3A/230Vac. Previous MC1000 and MC500 controllers had relay ratings of 1A/125Vac. However, these products are obsolete and no longer manufactured.

The RS485 protocol used on Monicon’s controllers is designed for simplicity and reliability. The RS485 communication interface allows the slave unit (i.e. control module) to be interrogated and some options programmed by a remote computer. Up to 100 units may be connected to the same RS485 interface. Each unit operates in polled slave mode. This means that the unit cannot initiate a communication, it can only respond when addressed by the master computer. The master computer broadcasts an address, a command code, a variable field and a checksum. The addressed slave unit then responds with its identification, a response identifier, a variable field and a checksum. To reduce the effect of interference from external electrical signals the RS485 interface uses a differential signal over a “twisted pair” cable. To further reduce the effects of interference, a low Baud rate of 2400 (or 1200) Baud is used. Finally, each communication is accompanied by a checksum. The use of a checksum ensures that if data corruption does occur, the information is disregarded and the information is transmitted again.

Monicon controllers are available for operation on either 230Vac or 115Vac. The default is 230Vac but the controllers may be fitted with 115Vac mains transformers if required.

Monicon’s Single Channel and Four Channel controllers offer voltage free relay contacts for alarm and fault conditions. In addition, they also offer an industry standard 4-20mA signal. Monicon’s Multichannel controllers offer voltage free relay contacts for alarm and fault conditions. They also offer an industry standard 4-20mA signal. They offer a range of open collector outputs to drive slave relays, mimic panel displays and annunciators. They also offer an RS485 digital serial interface where up to 100 channels may be looped together and interrogated by a host computer. For further details on the outputs on Monicon’s controllers, please see the relevant data sheets in the Products section or contact your local Monicon Distributor

The specifications for each controller are available on that controller’s data sheet. The data sheets may be downloaded in Adobe Acrobat PDF format from the Products section. Printed copies are available free of charge from your Distributor or direct from the factory if you e-mail your request to Monicon Technical Support.

The screen of the cable should normally be connected to 0V, ONLY at the controller and NOT at the detector. However, if the detector is mounted on a non-conductive surface, then the detector enclosure should be earthed locally OR through the cable screen. It is essential that electrical current does NOT flow in the detector cable screen as may happen if the screen was earthed at both ends.

Monicon’s controllers have an “auto-diagnostic” facility. The controller does a self-check 2-3 times every second. In the event of a failure such as a sensor fault, cable fault, low power or failure of certain key electronic components, the controller will initiate a FAULT alarm and indicate an error on the display.

Yes. The 4-20mA signal is linear with 4mA representing a zero gas concentration and 20mA representing a full scale gas concentration. An analogue outpus signal of in excess of 20mA indicates an overrange condition. 0mA indicates a fault condition, 2mA indicates “Calibration Mode”, 3mA indicates “Power Up” and 4mA indicates normal operation.

The CGS500 sensors use a thermocatalytic priciple to detect combustible gases and vapours. The sensing element consists of two coils of fine platinum wire coated in a catalyst to form beads.  One bead is the active bead and this bead will respond to gas concentrations. The other bead (the reference bead) is coated in a substance to render it non-reactive to gas. An electric current is passed through both beads in series and this current raises the temperature of  the beads. Combustible gas or vapour oxidising on the surface of the active bead will further raise the temperature of the active bead and thus change the electrical resistance of the platinum wire. The reference bead does not react to gas and is used to compensate for changes in external temperature, pressure, etc.

The Monicon IR100 Detector is an advanced NDIR (Non Dispersive Infra Red) detector incorporating a pulsed emitter, dual filters and dual detectors. This provides accurate and selective measurement of the gas being monitored. The technology is based on the measurement of the adsorption of infrared energy as it passes through a gas sample. Different gases have clearly defined absorption characteristics, their concentration can be determined by their absorption of infrared radiation at the wavelength determined by a narrow-band optical filter. To compensate for interfering factors (e.g. pressure, temperature, humidity variation, etc.) a second narrow-band filter isolates another wavelength which is used to measure the total transmission through the system and is not affected by the gas being monitored. By comparing the infrared energy reaching each of the two detectors, the concentration of the gas sample can be determined. A CPU processes and linearises these two signals and an analogue output signal is generated by a DAC, proportional to the gas concentration.

The T100 incorporates advanced SMD electronics and a 3 electrode electrochemical sensor based on micro fuel cell technology, designed to be maintenance free and inherently stable. The sensor uses the highly successful capillary diffusion barrier technology, resulting in a low temperature coefficient and a direct response to concentration, relatively unaffected by pressure. The use of electrodes based on fuel cell technology gives a high reserve of activity which results in long term stability. Gas diffusing to the sensor electrode reacts at the surface of the electrode either by oxidation (e.g. CO, H2S, SO2, NO, H2, HCN, HCl, O2, C2H4O, NH3) or by reduction (NO2, O3 and Cl2). Reactions are catalysed by specially developed electrode materials and are designed to be specific to the gas being sensed.

The CGS500 sensors are designed to measure gas in the range 0-100% of the LEL (Lower Explosive Limit)The Lower Explosive Limit of a gas is the concentration of that gas, in air at which that gas becomes explosive. This concentration is different for each gas.For example, the LEL of Methane is 5% by volume, while the LEL of propane is 2% by volume.The CGS500 sensors are designed to monitor concentrations of combustible gases and vapours BEFORE they become explosive.

The CGS500 sensors are designed to measure gas in the range 0-100% of the LEL (Lower Explosive Limit)The Lower Explosive Limit of a gas is the concentration of that gas, in air at which that gas becomes explosive. This concentration is different for each gas.For example, the LEL of Methane is 5% by volume, while the LEL of propane is 2% by volume.The CGS500 sensors are designed to monitor concentrations of combustible gases and vapours BEFORE they become explosive.

The main poisons for all thermocatalytic sensors are substances containing silicones, sulphurs, phosphurs and lead. However, there may also be other substances that will have an adverse effect on thermocatalytic sensors and your local Monicon distributor should be contacted if in doubt. In addition to poisons, there are also substances known as “inhibitors”. Inhibitors will not permanently damage the sensor but it will prevent the sensor from detecting combustible gases if an inhibitor is present. The most commonly encountered inhibitors are halocarbons such as freon or halon. If there is a likelyhood that there may be traces of poisons or inhibitors in the atmosphere to be monitored, we recommend that the Monicon CGS500-300P “Poison Resistant” sensor is used. This sensor is much better able to resist the effects of poisons and inhibitors in the atmosphere.

It is impossible to generalise as to where the detectors should be located as this may be different for each situation. There are various documents and standards published giving useful guidelines. However, in general, the following guidelines should be taken into consideration: The vapour density can indicate if a detector should be mounted near the ceiling or near the floor. Typically, to detect gases heavier than air (e.g. propane) the sensor should be mounted near the floor. To detect gases lighter than air (e.g. methane) the detector should be mounted near the ceiling. The air flow should also be considered when siting the detectors. Ventilation and other causes of air flow can affect the siting of the detectors. Devices that are likely to leak should be given consideration when positioning detectors. Boilers, gas tanks and gas cylinders for example, are potential leak points.

Yes. The CGS500 sensors will respond to a wide range of combustible gases and vapours. Further information on the sensitivity of these sensors to other gases is available in the Cross Sensitivity section or contact your local Monicon Distributor.