MTL7000 SERIES. Exceptionally high packing densities only 7mm barrier width

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1 MTL7000 SERIES ultra-slim safety barriers that can be used like terminals Exceptionally high packing densities only 7mm barrier width V dc supply connections simplified optional power comb feeds many barriers Direct connection of cable screens and lines third terminal on both hazardous and safe sides Patent US 887 MTL7000 Series award-winning, intrinsic safety shunt-diode safety barriers are innovative devices designed to provide exceptionally high packing densities, straightforward single-operation installation and simplified connection, commissioning and maintenance facilities. Many of the MTL7000 Series features duplicate the functions of conventional field terminals and the barriers can, therefore, double up as terminals for many applications, saving even more space. A barrier width of only 7mm enables maximum packing densities due to the use of surface mount and thick-film hybrid circuit technologies (subjects of patent applications). Barrier identification is provided by one or both of two methods. The first consists of tagging strips mounted on posts located at each end of a row of barriers while the other consists of separate identifiers attached to the tops of individual barriers. Of these, the first can be used to tag locations as well as barriers and is recommended for large installations while the second is better suited to installations of a few barriers only. An optional power comb simplifies installations where multiple barriers are powered from a common V dc source (via a power feed module or a dummy barrier). The comb replaces individual power supply connections to each barrier, yet allows single barriers to be removed without affecting the others. The power feed module powers up to 0 barriers and incorporates a trip which switches off the supply to the barriers if a fault (such as an overvoltage) occurs in the power source circuit. Secondary replaceable fuse versions of many barriers are available and form the MTL700 sub-series. These are useful where there is a possibility of faults occurring during commissioning which would otherwise blow the barriers' internal safety fuses. One secondary replaceable fuse for each barrier channel is provided and is lower in value than the related safety fuse. Fuses are packaged in small mouldings which can be latched in a 'disconnect' position to break the safe and hazardous s during commissioning, maintenance or fault finding, thus avoiding the need for additional disconnect terminals. Where a fuse is less likely to be necessary, the MTL700 sub-series uses a latchingout link only, to provide the basic loop disconnection of the MTL700 sub-series. EUROPE (EMEA) Tel: + (0)8 7 Fax: + (0)8 8 AMERICAS Tel: Fax: ASIA PACIFIC Tel: Fax: June 00

2 MTL7000 SERIES SPECIFICATIONS Key barriers shown in blue Model Safety Application Basic circuit Max. end- Vwkg at Vmax Internal safety No. description to-end 0µA fuse/fuse- MTL resistance disconnect(fd) (V) (Ω) (ma) (Ω) (V) (V) (ma) SINGLE CHANNEL +VE V dc systems (FD) } Controller outputs, (FD) solenoids 78P (FD) 79P+ 8 7 Controller outputs,.0. 0 (FD) solenoids (IIB) SINGLE CHANNEL VE For negative/ floating power supplies (FD) DOUBLE CHANNEL +VE V dc systems (FD) (FD) 7+ k Low-level/logic (FD) k return signals (FD) V dc systems (FD) 0 (FD) DOUBLE CHANNEL (NON-SYMMETRICAL) VE } Vibration probes (FD) (FD) RETURN-DIODE TYPE } Transmitters, diode controller outputs, + 0.9V switches (FD) 8 diode } + 0.9V (FD) 7087P Transmitters, 8 diode V controller outputs, 787P (FD) switches 8 diode + 0.9V (FD) SIMPLE AC, LOW LEVEL 70ac or -wire (floating) 0. at µa RTDs 0. at µa ac wire (grounded) 0. at µa RTDs 0. at µa at µa. 00 SIMPLE AC, HIGHER VOLTAGE 7ac Strain-gauge bridges wire RTD's } 70Pac Strain-gauge Pac 9 0 bridge, sense, output (FD) (FD) 7ac k Strain-gauge k bridge sense Pac 7 0 } Strain-gauge Pac 7 0 bridge supply (FD) (FD) EUROPE (EMEA) Tel: + (0)8 7 Fax: + (0)8 8 AMERICAS Tel: Fax: ASIA PACIFIC Tel: Fax: June 00

3 SPECIFICATIONS (continued) Model Safety Application Basic circuit Max. end- Vwkg at Vmax Internal safety No. description to-end 0µA fuse /fuse- MTL resistance disconnect (FD) (V) (Ω) (ma) (Ω) (V) (V) (ma) STAR-CONNECTED AC 700ac Active dc and ac sensors, ac thermocouples (FD) (FD) } } 7ac wire dc/ac ac systems ACTIVE BARRIERS Transmitters Transmitters Switches 8 +.V 0 8 diode + 0.9V Solenoids, alarms, 8 +.V 0 LEDs DUMMY BARRIERS 7099 Securing and earthing unused cables and screens. 799 Feed-through connections for power comb. All barriers have internal, inaccessible, safety fuses. MTL700 barriers have additional replaceable fuses, lower in value than the internal fuses. It is the value of the replaceable fuse that is quoted for MTL700 barriers. Note : Ω ±0.Ω at 0 C, channels track within 0.Ω from 0 to +0 C. Note : In star-connected barriers (eg, MTL700/70), the two channels are interlocked such that the voltage between them cannot exceed the working voltage, V wkg. Note : MTL778ac: the working voltage between the two interlocked channels is.; V max is.v. CERTIFICATION MTL7000 Series barriers protect devices located in all normally occurring explosive atmospheres, including air/flammable gasmixtures, dusts and fibres. MTL7000 Series barriers are certified [EEx ia] IIC (except MTL79P+, certified IIB) BY BASEEFA to CENELEC standards, by FM in the USA, CSA in Canada and also by other authorities, providing worldwide certification. MTL7000 Series barriers are designed to the same safety descriptions as MTL700 Series equivalents (in some cases slightly stricter) and can therefore be used for the same applications. HOW THEY WORK All MTL7000 Series barriers are based on the same simple principle. Each channel contains three stages of Zener or forward-connected diodes and an infallible terminating resistor. In the event of an electrical fault in the safe, the diodes limit the voltage that can reach the hazardous and the resistor limits the current: active output-current limiting circuits are not used. An internal fuse protects the diodes, and the three stages of voltage limitation ensure continued safety if the first or second stage should fail. MTL700 barriers have an additional replaceable fuse which protects the internal fuse. The MTL7000 Series includes seven key barrier types which cover the majority of applications, simplifying barrier selection and the maintenance of spares stocks. SUB-SERIES MTL7000 Series barrier circuits are based on the well-proven designs originally developed for the MTL700 Series. To simplify identification for those familiar with the latter, part numbers are the same for equivalent barriers, but with a 0, or inserted after the initial 7 to identify the relevant sub-series: Note : Limited availability. Use MTL770+ as an alternative. P suffix Barriers with a P suffix are higher-power versions of the standard devices with lower end-to-end resistance, except the MTL70Pac/7Pac. They are suitable for type IIC gas groups, except MTL79P+ which is designed for IIB. WARNING Check compatibility of the electrical safety parameters of the field equipment with those of the barriers to make sure that the combination is safe. MTL7000 MTL700 MTL700 standard fuse-disconnect link-disconnect Note: the circuit shown is as an example only. Standard, fuse- or link-disconnect options are shown shaded in the 'basic circuits' in the specifications tables. KEY BARRIERS SUMMARISED TYPE APPLICATION KEY BARRIER Analogue Resistance temperature detectors 70ac 700ac input (low level) Thermocouples, ac sensors 70ac Analogue Controller outputs, one line earthed output Controller outputs, neither line earthed dc power supply. 0-V Analogue Transmitters, -wire, /0mA input (high level) 787+ Digital (on/off) Switches input 787+ Digital (on/off) Solenoids, alarms, LEDs output 78+ EUROPE (EMEA) Tel: + (0)8 7 Fax: + (0)8 8 AMERICAS Tel: Fax: ASIA PACIFIC Tel: Fax: June 00

4 ACTIVE BARRIERS MTL70/MTL70, MTL707+ and 708+ active barriers The MTL70/MTL70, MTL707+ and 708+ barriers have built-in overvolt protection, allowing their use with unregulated power supplies. In many applications, eg, sensor inputs or controller outputs, there is insufficient power available to blow the barrier fuse and this additional protection is not necessary. But, where the barrier is connected to a power supply, eg, for energising transmitters, switches, solenoids or local alarms, overvolt protection allows the barriers to be used with unregulated supplies up to V dc and also gives protection against faulty wiring during commissioning. The MTL70, 707+, 708+ are equipped with a loop disconnect at power supply terminal while the MTL70 has a fuse-disconnect. Nearest equivalent passive barriers MTL70 nearest equivalent MTL78 /787+ MTL70 nearest equivalent MTL708 /7087+ MTL707+ nearest equivalent /787+ MTL708+ nearest equivalent MTL708+/78+ MTL70/70 for -wire /0mA and smart transmitters 00mA MTL70 Fuse disconnect The MTL70/MTL70 is a single-channel barrier designed primarily for energising a conventional or 'smart' -wire /0mA hazardous- transmitter. They can be thought of as an MTL78 or an MTL708 barrier with a built-in floating power supply and electronic over-volt protection. It provides a high voltage output (which is negative with respect to earth) to power the transmitter and delivers a /0mA signal into an earthed load in the safe-. The novel design is noted for its extreme accuracy. + /0mA 0mA /0mA MTL70 Loop disconnect link +0 to V Load resistor SPECIFICATION Supply voltage 0 to V dc Supply current 0mA typical at 0mA with 8V dc supply ma typical at 0mA with V dc supply 0mA maximum at 0mA with dc supply Voltage for transmitter and lines. minimum at 0mA with 0Ω load.v minimum at 0mA with 00Ω load Note that the output voltage is negative with respect to earth. Safe- load resistance 0 to 00Ω Output current 0 to.ma Accuracy ±µa ( to 0mA) Out of range capability Over-range; >0mA to.ma Under-range; <ma to 0mA Smart compatibility HART Communication Foundation HART Honeywell DE Yokogawa BRAIN Foxboro smart Fuji smart Chessel 00 Series Patent Nos UK: 099 European (Germany, France, Italy): EP BI USA: 970 HART is a registered trademark of HART Communication Foundation EUROPE (EMEA) Tel: + (0)8 7 Fax: + (0)8 8 AMERICAS Tel: Fax: ASIA PACIFIC Tel: Fax: June 00

5 MTL707+ for digital (switch) inputs Loop disconnect link Current limit SPECIFICATION Supply voltage, terminal +0 to +V dc Normal operation In normal operation the protection circuit introduces only a small voltage drop and shunts less than.ma to earth, so its overall effect is minimal Supply voltage >7V If the supply voltage exceeds about 7V, causing the Zener diodes to conduct, or if the safe- load has a very low resistance, the supply current is limited automatically to <0mA. This protects the fuse and power supply and enables the loop to continue working. Supply current At Vs <V; Iout +.ma max At Vs >8V or low load resistance; limited to <0mA Internal fuse, terminal 0mA Reverse voltage protection, terminal Yes 0mA + I out.ma max 0 to V dc max 0mA Maximum voltage drop, terminals to [(Iout x 8Ω) +.]V (current not limited) Output current (Iout), terminal Up to ma Leakage to earth.ma max Internal fuse, terminal 0mA Maximum voltage drop, terminals to [(I out x Ω) + 0.9]V MTL708+ for digital (switched) outputs Loop disconnect link Current limit SPECIFICATION Supply voltage, terminal +0 to +V dc Normal operation In normal operation the protection circuit introduces only a small voltage drop and shunts less than.ma to earth, so its overall effect is minimal Supply voltage >7V If the supply voltage exceeds about 7V, causing the Zener diodes to conduct, or if the safe- load has a very low resistance, the supply current is limited automatically to <0mA. This protects the fuse and power supply and enables the loop to continue working. Supply current At Vs <V; Iout +.ma max At Vs >8V or low load resistance; limited to <0mA Internal fuse, terminal 0mA Reverse voltage protection, terminal Yes Maximum voltage drop, terminals to [(Iout x 0Ω) +.]V (current not limited) Output current (Iout), terminal Up to ma Leakage to earth.ma max LED, alarm, solenoid, etc 0mA + I out.ma max 0 to V dc max EUROPE (EMEA) Tel: + (0)8 7 Fax: + (0)8 8 AMERICAS Tel: Fax: ASIA PACIFIC Tel: Fax: June 00

6 MTL799 power feed module Green power LED Solid-state switch Current sense Voltage sense Trip circuit 800mA max Red fault LED To barriers via power comb External power supply 0 to.8v dc at.8a min The MTL799 power feed module incorporates both voltage and current sense mechanisms to protect barrier circuits by activating a solid-state trip mechanism when fault or overload conditions occur in the power source circuit. Resetting the module after tripping is done by interrupting the supply to the unit. A red LED indicates a circuit trip condition and a green LED the availability of power at the outputs. SPECIFICATION Input voltage range (terminals and ) 0 to.8v Maximum input voltage capability V Power source requirement Power source must be capable of delivering at least.8a Trip mechanism Minimum trip operating voltage:.8v (at 0 C ambient) at output terminal wrt earth Temperature coefficient: +8.mV/ C MTL799 Output current range (terminal wrt earth) 0 to 800mA LED indication Green: indicates power at output terminals (ie, power being fed to barriers) Red: indicates trip condition (ie, overvoltage or overcurrent state) Maximum voltage drop 0mV at 0mA load, 0 to +0 C. at 800mA load, 0 to +0 C Maximum number of barriers powered Load dependent, eg: 0 x * at 0mA (/0mA loops) * Or fuse-disconnect or P versions GENERAL SPECIFICATION Ambient temperature limits 0 to +0 C (FM/CSA) continuous working 0 to +0 C (BASEEFA) continuous working 0 to +80 C storage Humidity limits to 9% RH Case flammability UL9: V- Terminations Terminals accommodate conductors up to.mm - terminals are identified as dark blue Colour coding of barrier type (label on top surface) Red: Positive polarity (+) Black: Negative polarity ( ) Black (with red text): MTL70/70 Grey: Non-polarised (ac) White: MTL7099/799 dummy barrier Orange: MTL799 power feed module Weight 00g approximately Mounting and earthing Clamping onto standard mm 'top-hat' DIN-rail: 7.mm (low profile) or mm (high profile) DIMENSIONS (mm) 0. terminals MTL7XXX Fuse/link positions (MTL700/700) Safe- terminals 0. (7.mm rail) 09. (mm rail) 99 Installation and approval side label Note: All specifications quoted at 0 C ambient unless otherwise stated. Colour-coded top label Channel (terminal to ) Channel (terminal to ) MTL7XXX EUROPE (EMEA) Tel: + (0)8 7 Fax: + (0)8 8 AMERICAS Tel: Fax: ASIA PACIFIC Tel: Fax: June 00

7 MTL7000 SERIES BARRIER APPLICATIONS ANALOGUE INPUTS (HIGH-LEVEL) -wire transmitters, /0mA, conventional and smart Recommended barriers for use with 'conventional' and 'smart' /0mA transmitters (fed by a regulated supply) are the /787+ or /787P+. These provide up to.v at V wkg and 0mA for a transmitter and its lines as well as V for the typical 0Ω load. This application and these barriers are suitable for use with the optional power comb. The MTL70/70 is recommended for applications where an unregulated supply of up to V is used. It provides. for transmitter and lines at 0mA as well as V for a typical 0Ω load. With the MTL70/70 terminal is negative with respect to earth, so the connections to terminals and should be reversed. MTL7000 Series barriers protect devices located in all normally occurring explosive atmospheres, including air/flammable gas mixtures, dusts and fibres. Applications covered include the protection of installations incorporating uncertified devices ( simple apparatus ) such as thermocouples, switches and resistive sensors, or separately certified energy storing (or voltage producing ) apparatus including ac sensors, transmitters and current-to-pneumatic (I/P) converters. Recommended choices for specific applications are discussed briefly in the following pages. These are examples, and many other configurations will suggest themselves. For advice on a particular application, please contact MTL. MTL787+ MTL787P+ MTL70 MTL70 /0mA +V V 0Ω Vibration probes The -wire transmitters used with vibration monitoring equipment are invariably supplied by a V dc power supply hence the recommended barrier choice is the negatively-polarised MTL709 /79. The third terminal makes this choice ideal for these -wire applications. Probe driver Transducer MTL709 MTL79 Monitor V V out ANALOGUE INPUTS (LOW-LEVEL) Thermocouples and mv sources The recommended barrier for thermocouples and mv sources is the MTL700ac/70ac. This -channel non-polarised barrier retains the earth-free nature of the signal and, providing the receiver s input floats, rejects common-mode ac and dc interference up to at least 7V and is unaffected by earth faults on the primary element. Compensating cable MTL700ac MTL70ac Recorder Controller Data logger Computer ac sensors, photocells, microphones and turbine flowmeters The MTL700ac/70ac is the recommended choice for these devices. While many of these are designated simple apparatus and thus do not need certification, note that some ac sensors may be subject to a significant level of inductance and will therefore need to be designed and certified for hazardous- locations. Photocell Microphone Turbine flowmeter MTL700ac MTL70ac Earth free signal Slidewire displacement transducers The simplest choice is the MTL700ac/70ac. This barrier supplies power and brings back a unipolar signal. MTL700ac MTL70ac +7.V V out EUROPE (EMEA) Tel: + (0)8 7 Fax: + (0)8 8 AMERICAS Tel: Fax: ASIA PACIFIC Tel: Fax: June 00

8 RTDs For -wire RTDs, a single MTL70ac barrier is the most economical choice. This is suitable for use with a floating bridge the two leads from the bridge arms are protected by the barrier with the third (supply) lead being earthed through the barrier. The barrier has a low end-to-end resistance of only Ω/channel to minimise span changes and its channels track within 0.Ω (between 0 to +0 C) to minimise zero shift with temperature. MTL70ac Receiver If the bridge circuit is already earthed, the third barrier channel provided by an MTL70ac is needed. For extreme accuracy, channels and an earth-free bridge can be used, a configuration that cancels out the small errors due to barrier leakage. Channels and (those between terminals &, and & respectively) track to within 0.Ω between 0 and 0 C. MTL70ac Receiver -wire constant-current circuits do not need matched barrier resistances and can be protected by two MTL7ac barriers. If the increase in loop resistance is too great, use two MTL70ac barriers instead. MTL7ac MTL70ac Receiver MTL7ac MTL70ac STRAIN-GAUGE BRIDGES Single strain-gauge bridges This shows an arrangement using two or three barriers, which is safe in IIC gases. With the MTL7ac, the circuit is powered from a V, 0Ω source; if the bridge resistance is 0Ω, then the bridge voltage is 7V. If the bridge resistance is 0Ω, then the bridge voltage is 8.V. +7V 7V An MTL7ac can be used to sense the bridge supply voltage. MTL7ac An MTL7ac is used here for the mv output. An MTL7Pac provides.v for a 0Ω bridge with a supply. MTL7Pac's can be used for the sense and pick-off circuits. + Sense MTL7ac Output (mv) MTL7ac EUROPE (EMEA) Tel: + (0)8 7 Fax: + (0)8 8 AMERICAS Tel: Fax: ASIA PACIFIC Tel: Fax: June 00

9 Double strain-gauge bridges Quite frequently there is a demand to monitor two load cells, and a possible circuit, safe in IIC, is shown. Here, the lower voltage drop of the MTL70Pac is an advantage. The MTL70Pac supplies power to the bridge(s) whilst two MTL70Pac/7Pac barriers interface with the sense and pick-off circuits. MTL70Pac + Using 0Ω bridge systems, the following voltages are available from an MTL70Pac with a ± supply: bridge:.8v bridges: 9.V MTL70Pac MTL7Pac + Sense Output (mv) MTL70Pac MTL7Pac ANALOGUE OUTPUTS Controller outputs (I/P converters) The single-channel MTL708+/78+ with a voltage drop of.7v/.9v is the recommended choice for most controller outputs. Higher-power versions are available: the MTL78P+ (.V drop) is suitable for IIC applications; the MTL79P+ (.V drop) for IIB applications. P I MTL708+ MTL78+ MTL78P+ *MTL79P+ +V For controllers with an output circuit separated from the rail by the control transistor, the -channel /787+ is the preferred choice as the return channel can handle up to./. allowing the control signal to be turned off completely. The voltage drop is 8.V/8.V at 0mA. A higher-power version of the latter, the /787P+, is also available. The return channel of these barriers handle up to./. and the maximum voltage drop is only.7v/7.v. The /787+ and /787P+ are also suitable for controllers containing a resistor which enables the return current to be monitored for high-integrity operation. P I P I MTL787+ MTL787P+ MTL787+ MTL787P+ * CENELEC gas group IIB (C & D N. America) +V +V Monitor rail EUROPE (EMEA) Tel: + (0)8 7 Fax: + (0)8 8 AMERICAS Tel: Fax: ASIA PACIFIC Tel: Fax: June 00

10 DIGITAL (ON/OFF) INPUTS Switches The normal choice is the /787+ with a regulated supply. The MTL707+ is recommended for applications where an unregulated supply of up to V is used. For optimum power transfer, with relays the resistance of the load should be approximately equal to the combined resistance of the two channels and the relay coil should then be rated at about half the supply voltage. MTL787+ MTL707+ +V Logic signal DIGITAL (ON/OFF) OUTPUTS Alarms, LEDs, solenoids valves, etc For these applications, the MTL708+/78+ is recommended. Higher-powered versions are available: the MTL78P+ is suitable for IIC applications; the MTL79P+ for IIB applications. The MTL708+ is recommended for applications where an unregulated supply of up to V is used. If the control switch is to earth, then the -channel /787+ barrier should be used, or, alternatively, the /787P+ higher-power version. If the supply is poorly regulated use the MTL707+. LED, alarm LED, alarm MTL708+ MTL78+ MTL78P+ *MTL79P+ MTL708+ +V *CENELEC gas group IIB (C & D N. America) +V MTL787+ MTL787P+ MTL707+ +VE DC SYSTEMS Low-level to V dc systems The two channels of the MTL7+, MTL7+ and MTL77+ can be combined safely in IIC. The MTL7+ can be used for low-level logic return signals. The MTL7+ and MTL77+ are used for V dc and V dc systems respectively. dc systems MTL7+ MTL7+ MTL77+ +V/9V/V +V/9V/V 8V dc systems The single-channel MTL7+ is recommended for 8V dc systems. dc systems +8V MTL7+ AC AND DC SYSTEMS High-level ac and dc systems The versatile star-connected MTL7ac and MTL778ac allow V wkg to be developed from each channel to ground but only allow V wkg to be developed between channels. This provides some common-mode voltage capability and can allow higher cable parameters to be used. dc and ac systems MTL7ac MTL778ac V/V NEGATIVE AND FLOATING POWER SUPPLIES Digital (on/off) outputs The MTL708 /78 is used with a negative power supply and positive earth. Typically used for digital inputs or outputs, as shown. The MTL708-/78- can also be used with floating power supplies, for transmitters. LED, alarm MTL708 MTL78 + V EUROPE (EMEA) Tel: + (0)8 7 Fax: + (0)8 8 AMERICAS Tel: Fax: ASIA PACIFIC Tel: Fax: June 00

11 POWER COMB APPLICATIONS The PWC7000 power comb is invaluable for saving installation time and wiring when connecting a V dc power source to a number of barriers. Typical applications include hazardous- switches, /0mA transmitters and solenoids. The diagram illustrates the configuration for barriers but up to 0 barriers can be served by this method. MTL799 OR MTL7099 MTL799 External V dc supply The MTL799 power feed module would normally be used with standard barriers such as and because the current/voltage trip protection mechanism of the MTL799 removes the need for replaceable fuses in the barriers. The MTL7099/799 dummy barriers can be used instead of the MTL799 for direct feed-through connection of a V dc supply. In these circumstances, replaceable fuse barriers such as MTL787+ and MTL787P+ may be preferred. MTL787+ MTL787P+ Logic signal The MTL799 dummy barrier has a removable link between terminals and for easy disconnection of the supply. Other units which can use the power comb: MTL70 MTL70 MTL707+ MTL708+ MTL787+ MTL787P+ Logic signal MTL787+ MTL787P+ Logic signal Power comb PWC7000 SPARE CABLE CORES AND SCREENS The MTL7099/799 dummy barriers are used primarily for securing and earthing unused cables and screen connections. terminals, and (and safe terminal ) are internally connected to the DIN-rail mounting/earth connection. Unused cable cores and screens MTL7099 MTL799 WIRED IN APPLICATIONS MTL799s can be 'looped-in' to provide link-disconnects for MTL70xx barriers, eg. as shown here with an MTL70ac and an RTD. For high accuracy or sensitive low level applications check that the additional connections do not degrade the signals. MTL70ac MTL799 Receiver MTL799 EUROPE (EMEA) Tel: + (0)8 7 Fax: + (0)8 8 AMERICAS Tel: Fax: ASIA PACIFIC Tel: Fax: June 00

12 MAXIMUM CABLE PARAMETERS Model no. Number of single Maximum permissible cable parameters channels interconnected Earth BASEEFA (group IIC (hydrogen)) FM (Groups A & B) Matched within return Capacitance Inductance L/R ratio Capacitance Inductance power hazardous used? (µf) (mh) (µh/ω) (µf) (mh) (W) MTL70/70 Yes MTL707+ Yes MTL708+ Yes MTL7+ Yes MTL708+/78+ Yes MTL78P+ Yes MTL708 /78 Yes MTL79P+ Yes IIB (C&D) only MTL70ac Yes Yes No No Yes MTL70ac Yes No MTL700ac/70ac Yes Yes MTL70Pac/7Pac No MTL7ac Yes Yes MTL7+ Yes Yes No MTL7+ Yes Yes MTL7ac Yes Yes No MTL7ac Yes Yes MTL70Pac/7Pac Yes MTL77+ Yes Yes MTL778ac Yes Yes /787+ Yes /787P+ Yes MTL709 /79 Yes Notes Key barriers in bold If values are not quoted for when on earth return is not used, then those for an earth return ('Yes' in the tables) are applicable For most practical purposes, the values of the parameters for groups IIB and IIA are respectively and 8 times the values for group IIC The maximum power that can be drawn from the barrier or barrier combination under fault conditions; used for assessing the temperature classification of simple' hazardous- apparatus TERMINOLOGY Safety description The description of a barrier, eg, 0ž 00mA, refers to the maximum voltage of the terminating Zener or forward diode when an internal safety fuse is blowing, the minimum value of the terminating resistor, and the corresponding maximum short-circuit current. It is an indication of the fault energy that can be developed in the hazardous and not of the working voltage or end-to-end resistance. Polarity Barriers may be polarised positive ( + ) or negative ( ) or nonpolarised ( ac ). Polarised barriers accept and/or deliver safe- voltages of the specified polarity only. Non-polarised barriers support voltages of either polarity applied at either end. The exception is the MTL70 which takes a positive supply but provides an output voltage which is negative with respect to earth. End-to-end resistance The resistance between the two ends of a barrier channel at 0 C, ie, of the resistor and the fuse(s). If diodes or transistors are present, the voltage drop of these is also quoted. Working voltage (Vwkg) The greatest steady voltage, of appropriate polarity, that can be applied between the safe- terminal of a basic barrier channel and earth at 0 C for the specified leakage current, with the hazardous- terminal open circuit. Maximum voltage (Vmax) The greatest steady voltage, of appropriate polarity, that can be applied continuously between the safe- terminal of any barrier channel and earth at 0 C without blowing the internal safety fuse/external replaceable fuse (MTL700). For basic barriers it is specified with the hazardous- terminal open circuit; if current is drawn in the hazardous, the maximum voltage for these barriers is reduced. The ac channels of basic barriers withstand voltages of the opposite polarity also see the circuit diagrams included under Applications. Fuse ratings The greatest current that can be passed continuously through the fuse for 000 hours at C. Maximum safe- voltage (U m ) The maximum permissible safe- voltage (U m ) for MTL7000 Series barriers is ac/dc. EUROPE (EMEA) Tel: + (0)8 7 Fax: + (0)8 8 AMERICAS Tel: Fax: ASIA PACIFIC Tel: Fax: June 00

13 HOW TO ORDER MTL7000/700/700 barriers Select by barrier number and polarity, e.g. MTL708+ Mounting accessories THR Standard DIN-rail, x 7.mm THR7000 T-section DIN-rail, specially-plated, x 7.mm, m length ISP7000 Insulating spacer Standard earthing/earth-rail accessories ETL7000 Earth terminal, DIN-rail mounted IMB7 Insulating mounting block ERB7S Earth-rail bracket, straight ERB7O Earth-rail bracket, offset ERL7 Earth rail, m length ETM7 Earth terminal, pack of 0 Replaceable fuses/removable links RFA700 Replaceable fuse assemblies, 0mA, pack of RFA700 Replaceable fuse assemblies, 00mA, pack of RLA7000 Removable link, pack of Enclosures DX070 Enclosure, for MTL7000 x 9 DX70 Enclosure, for MTL7000 x DX0 Enclosure, for MTL7000 x 8 Literature INM7000 Instruction manual, MTL7000 Series INM7ENC Instruction manual, MTL000/7000 Series Enclosures CD Customer drawings Standard tagging accessories TAG7 Tagging strip, m length TGL7 Tagging strip labels, set of 0 x 0.m BRI7000 Barrier identifier BIL7000 Barrier identification labels, sheet of 0 BIL7000L Barrier identification labels, A sheet of CORRELATION BETWEEN MTL7700 MTL7000 MTL700 BARRIERS (IIC) Module No. Bussed MTL7000 MTL7000 MTL7000 MTL700 MTL700 MTL700 Typical Power? Equivalent Original ATEX equivalent Original ATEX Application Certificate Certificate Certificate Certificate Number(s) Number(s) Number(s) Number(s) MTL770+/- No Half of Ex9C BAS99ATEX78 MTL70+/- Ex8 BAS0ATEX70 /V MTL7+/- Systems MTL77+/- No N/A N/A N/A MTL7+/- Ex8 BAS0ATEX70 V Systems MTL77P+/- No N/A N/A N/A MTL7P+ Ex9C7 BAS0ATEX70 V Systems MTL77+/- No MTL7+/- Ex9C BAS99ATEX78 MTL7+/- Ex8 BAS0ATEX70 General Purpose MTL778+/- No MTL708+/- Ex9C BAS99ATEX78 MTL78+/- Ex8 BAS0ATEX70 Analogue / Digital MTL78+/- MTL778ac No N/A N/A N/A MTL78ac Ex8 BAS0ATEX70 General Purpose MTL778P+/- No MTL78P+/- Ex9C BAS99ATEX78 MTL78P+ Ex9C7 BAS0ATEX70 Analogue / Digital MTL77ac No MTL70ac Ex9C BAS99ATEX78 MTL7ac Ex8 BAS0ATEX70 RTD, Grounded MTL77ac No MTL70ac Ex9C BAS99ATEX78 N/A N/A N/A RTD, Grounded MTL770ac No N/A N/A N/A MTL70ac Ex8 BAS0ATEX70 Active sensors, Thermocouples MTL77ac No MTL7ac Ex9C BAS99ATEX78 MTL7ac Ex8 BAS0ATEX70 Strain Gauges MTL77Pac No MTL70Pac Ex9C BAS99ATEX78 MTL7Pac Ex9C7 BAS0ATEX70 Load cell MTL7Pac MTL77+/- No MTL7+/- Ex9C BAS99ATEX78 MTL7+/- Ex8 BAS0ATEX70 High resistance MTL77ac No MTL7ac Ex9C BAS99ATEX78 MTL7ac Ex8 BAS0ATEX70 Strain / Level Gauges MTL77ac No N/A N/A N/A MTL7ac Ex8 BAS0ATEX70 General Purpose MTL77ac No N/A N/A N/A MTL7ac Ex8 BAS0ATEX70 Strain Gauges MTL77Pac No MTL70Pac Ex9C BAS99ATEX78 MTL7Pac Ex9C7 BAS0ATEX70 Strain Gauges MTL7Pac MTL777+/- No MTL77+/- Ex9C BAS99ATEX78 MTL77+/- Ex8 BAS0ATEX70 Dual MTL7 MTL7779+/- No N/A N/A N/A MTL779+/- Ex8 BAS0ATEX70 Dual MTL78 MTL7787+/- Yes /- Ex9C BAS99ATEX78 MTL787S+ Ex8 BAS0ATEX70 Analogue / Digital MTL787+/- MTL7787P+/- Yes Ex9C BAS99ATEX78 MTL787SP+ Ex9C7 BAS0ATEX70 Analogue / Digital MTL787P+ MTL7788+/- Yes N/A N/A N/A MTL788+/- Ex8 BAS0ATEX70 Transmitters MTL7788R+/- Yes N/A N/A N/A MTL788R+/- Ex8 BAS0ATEX70 V systems MTL779+/- No MTL709+ Ex9C BAS99ATEX78 MTL79+/- Ex8 BAS0ATEX70 Gas Metering MTL79- EUROPE (EMEA) Tel: + (0)8 7 Fax: + (0)8 8 AMERICAS Tel: Fax: ASIA PACIFIC Tel: Fax: June 00