Mtl700 Series: For Safe Measurement and Control in Hazardous Areas
Mtl700 Series: For Safe Measurement and Control in Hazardous Areas
Mtl700 Series: For Safe Measurement and Control in Hazardous Areas
MTL700 SERIES
EUROPE (EMEA)
Tel: +44 (0)1582 723633
Fax: +44 (0)1582 422283
AMERICAS
Tel: +1 281 571 8065
Fax: +1 281 571 8069
ASIA PACIFIC
Tel: +65 6 487 7887
Fax: +65 6 487 7997
E-mail: enquiry@mtl-inst.com
Web site: www.mtl-inst.com
Jun 2009
Safety description
Polarities
available
Application
Basic circuit
Hazardous
MTL
mA
702
706
707
25
28
28
28
28
15
28
200
300
300
diode
164
diode
300
125
93
93
170
93
10
10
15
15
22
22
28
28
28
28
50
33
100
50
150
101
300
300
234
164
200
300
150
291
147
213
93
93
119
170
1
1
3
3
10
10
10
10
100
100
300
300
7.5
7.5
9
9
9
9
12
12
12
12
12
12
15
15
22
22
28
28
26
20
10
10
90
90
350
350
1k
1k
150
150
75
75
100
100
150
150
300
300
300
390
750
750
100
100
25
25
12
12
80
80
157
157
150
150
147
147
93
93
87
51
10
10
15
15
22
22
28
28
50
50
100
100
300
300
600
600
200
200
150
150
73
73
47
47
786
28
28
diode
diode
Signal returns
787
28
28
28
28
300
diode
300
diode
93
93
Controller outputs,
switches
Transmitters
Controller outputs, switches
28
28
234
diode
119
28
10
300
50
93
200
28
10
300
50
93
200
707P
708
710
710P
715
715P
722
722P
728
728P
729P
751
755
758
761
761P
764
766
766P
767
768
779
796
760
765
772
778
Transmitters
Transmitters
Switches
Safe
ac
Transmitters, switches,
controller outputs
Solenoids, alarms, LEDs,
switches
6V dc & 4V ac systems
8V dc systems
12V systems
12V dc systems
18V dc systems
18V dc systems
Controller outputs, solenoids
Transmitters
Controller outputs, solenoid valves
Controller outputs, solenoid valves
18V dc systems
Controller outputs
Vibration probes
(MTL796 negative)
787SP
788
11
11
51
51
216
216
2.0
2.0
3.6
3.6
250
250
250
250
18
18
145
145
384
384
1075
1075
185
185
93
93
155
155
185
185
340
340
340
435
6.0
6.0
6.0
6.0
7.0
7.0
10.0
10.0
10.0
10.0
9.8
9.8
12.0
12.0
19.0
19.0
25.5
25.5
23.5
17.5
7.0
7.0
7.5
7.5
8.1
8.1
10.7 e
10.7 e
11.2
11.2
11.3
11.3
13.0
13.0
20.2
20.2
26.6
26.6
24.6
18.7
200
200
100
100
50
50
50
50
50
50
100
100
100
100
50
50
50
50
50
50
85
85
135
135
340
340
665
665
6.0
6.0
12.0
12.0
18.0
18.0
24.0
24.0
7.4
7.4
13.2
13.2
19.7
19.7
25.7
25.7
50
50
50
50
50
50
50
50
2.2V+30
2.2V+30
25.5
25.5
26.6
26.6
50
50
340
2.2V+30
340
0.9V+20
25.5
25.5
25.5
25.5
26.6
26.6
26.6
26.6
50
50
50
50
258
0.9V+16
24.5
24.5
26.5
26.5
80
80
340
85
340
85
25.5
6.0
25.5
6.0
26.6
6.9
26.6
6.9
50
50
50
50
1
ac
4 (20V:796)
Star connected
787S
250
4 (10V)
31.25kbit/s fieldbus
installations
50
3 (28V)
they
work
See
'How
62.6
62.6
Internal
terminator
4
799
0.3
0.3
(0.6)
(0.6)
791
20
20
18.0a
18.0a
*
4
ac
Transmitters
788R
26.0
26.0
787S
24.5
24.5
50
200
100
200
50
100
50
50
100
100
See additional
specification
6.9 c
9.2
13.0
13.8
20.2
20.0
26.6
26.6d
mA
6.0
8.0
12.0
12.5
19.0
18.5
25.5
25.5b
Strain-gauge
bridges
Strain-gauge bridges
85
42
155
60
185
121
340
340
253
184
Strain-gauge
bridges
12V dc systems
Fuse
rating
3 (26V:796)
Vmax
BARRIERS'
Vwkg at
10(1)A
35
35
35
50
35
35
'OVERVOLT-PROTECTED
Gas detectors
Max. endto-end
resistance
100
100
2
1
Terminal
1&2
open
circuit
Jun 2009
1. Safety description
The safety description of a barrier, eg 10V 50 200mA, refers to
the maximum voltage of the terminating Zener or forward diode while
the 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 area, and
not of the working voltage or end-to-end resistance.
2. Polarity
Barriers may be polarised + or , or non-polarised (ac). Polarised
barriers accept and/or deliver safe-area voltages of the specified
polarity only. Non-polarised barriers support voltages of either
polarity applied at either end. An exception to this is the MTL791
Fieldbus barrier which has one positive and one negative channel.
3. End-to-end resistance
The resistance between the two ends of a barrier channel at 20C, ie
of the resistors and the fuse. If diodes or transistors are present, their
voltage drop (transistors ON) is quoted in addition.
DIMENSIONS (mm)
3
4
TERMINOLOGY
GENERAL SPECIFICATION
25.0
7.5
Hazardous-area
terminals
7.5
Safe-area
terminals
9.0
61.5
49.2
6. Fuse rating
The greatest current that can be passed continuously (for 1000 hours
at 35C) through the fuse.
7. Star connection
In star-connected barriers, the two channels are interlocked such that
the voltage between them cannot exceed the working voltage, Vwkg:
this allows for higher cable capacitance or inductance.
8. Maximum safe-area voltage (Um)
The maximum permissible safe-area voltage (Um) for MTL700 Series
barriers is 250V ac/dc.
11.5
85.0
93.5
14.2
TYPE
Analogue
input (low-level)
Analogue
output
KEY BARRIER
755ac
760ac
728+
787S+
dc power supply
26.0V
2035V
Analogue
Transmitters, 2-wire, 4/20mA
input (high-level)
787S+
706+
Digital (on/off)
input
Switches
787S+
707+
Digital (on/off)
output
728+
708+
EUROPE (EMEA)
Tel: +44 (0)1582 723633
Fax: +44 (0)1582 422283
AMERICAS
Tel: +1 281 571 8065
Fax: +1 281 571 8069
ASIA PACIFIC
Tel: +65 6 487 7887
Fax: +65 6 487 7997
E-mail: enquiry@mtl-inst.com
Web site: www.mtl-inst.com
Jun 2009
OVERVOLTPROTECTED BARRIERS
The MTL702+, 706+, 707+, 707P+ and 708+ 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. However, 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 35V dc and also gives protection
against faulty wiring during commissioning.
OVERVOLT-PROTECTED
BARRIERS
BASIC CIRCUIT
Hazardous area
Safe area
performance but did not pass outgoing communication signals below about
1kHz.
60mA max
Current
+35V max.
1
100mA
BASIC CIRCUIT
Hazardous area
mirror
3
+V ref
50mA
Tx
4/20mA
Regulate
Safe area
4/20mA
Current limit
ADDITIONAL SPECIFICATION
Tx
4/20mA
4/20mA
50mA
50mA
Regulate
Negative
0V
Supply voltage
20 to 35V dc, positive w.r.t. earth
Voltage available for transmitter and lines (at 20mA)
(Vsupply 8V), limited at 16V
Voltage available for load (at 20mA)
Vsupply 5V
Load resistance
850 maximum
Output impedance to load
>1M
load)
Calibrated accuracy (at 20C with 250
0.05% of maximum output, including non-linearity and
hysteresis
Zero temperature drift
<0.005% of maximum output per C
Span temperature drift
<0.005% of maximum output per C
Supply current
8 to 40mA + 10mA max. at 20V
8 to 40mA + 20mA max. at 35V
+35V max.
1
40mA max
50mA 2
850
max.
50mA 2
250
5%
0V
ADDITIONAL SPECIFICATION
Supply voltage
20 to 35V dc, positive w.r.t. earth
Output current
4 to 20mA
Voltage available for transmitter and lines
15V minimum at 20mA with 22V supply
15.5V typical at 20mA with 24V supply
Note: voltages are negative w.r.t. earth
Load resistance
250 5% (can be greater if reduced transmitter voltage is
acceptable)
Accuracy
2A under all conditions
Supply current
35mA typical
at 20mA with 24V supply
40mA maximum at 20mA with 35V supply
EUROPE (EMEA)
Tel: +44 (0)1582 723633
Fax: +44 (0)1582 422283
AMERICAS
Tel: +1 281 571 8065
Fax: +1 281 571 8069
ASIA PACIFIC
Tel: +65 6 487 7887
Fax: +65 6 487 7997
E-mail: enquiry@mtl-inst.com
Web site: www.mtl-inst.com
April 2006
BASIC CIRCUIT
OVERVOLT-PROTECTED
BARRIERS
Hazardous area
(continued)
Tx,
switch,
etc.
Safe area
3
Current
limit
1
50mA
+35V max
2mA
max
I out
50mA 2
Safe area
I out
BASIC CIRCUIT
Hazardous area
ADDITIONAL SPECIFICATION
Current
limit
50mA
1 mA max
50mA
ADDITIONAL SPECIFICATION
Supply voltage (Vs)
10 to 35V dc, positive w.r.t. earth
Output current (Iout)
Up to 35mA available
Maximum voltage drop (at 20C, current not limited)
Iout x 370 + 1.5V, terminal 1 to 3
Iout x 50 + 2.1V, terminal 4 to 2
Supply current
Iout + 1mA max, Vs <26V
Limited at 50mA, Vs >28V or low load resistance
BASIC CIRCUIT
Hazardous area
Safe area
3
LED,
alarm,
solenoid,
etc
Current
limit
I out
1
+35V max
50mA
1 mA max
ADDITIONAL SPECIFICATION
Supply voltage (Vs)
10 to 35V dc, positive w.r.t. earth
Output current (Iout)
Up to 35mA available
Maximum voltage drop (at 20C, current not limited)
Iout x 370 + 1.5V, terminal 1 to 3
Supply current
Iout + 1mA max, Vs <26V
Limited at 50mA, Vs >28V or low load resistance
EUROPE (EMEA)
Tel: +44 (0)1582 723633
Fax: +44 (0)1582 422283
AMERICAS
Tel: +1 281 571 8065
Fax: +1 281 571 8069
ASIA PACIFIC
Tel: +65 6 487 7887
Fax: +65 6 487 7997
E-mail: enquiry@mtl-inst.com
Web site: www.mtl-inst.com
Jun 2009
Hazardous area
Safe area
MTL760ac
Insulated
from earth
10V
10V
21
34
The preferred barrier for thermocouples is the MTL760ac, whose 2channel non-polarised design retains the earth-free nature of the
signal. Provided that the receivers input circuit floats, the combination
rejects common-mode ac and dc interference up to at least 6V and is
unaffected by earth faults on the primary element. Even if the
receivers circuit is tied to its 0V rail, the use of a 2-channel barrier
takes the worry out of earthing. To eliminate errors due to thermal
emfs, the compensating cable should be continued from the barrier to
the receiver. For moving coil or other low resistance receivers, use the
MTL751 (40) or the MTL755ac (36) if the resistance of the
MTL760 (170) is unacceptable.
Recorder,
controller,
data logger,
computer
Fig. 1
Compensating cable
34
21
Temperature transmitter
Fig. 2
34
Photocell,
microphone,
turbine
flowmeter, etc
10V
10V
MTL760ac
Earthfree
signal
21
Fig. 3
L
N
E
MTL755ac
21
34
3V
3V
Receiver
Fig. 4
34
21
34
3V
3V
21
1 /2 MTL755ac
Receiver
Fig. 5
34
21
MTL761ac
MTL755ac
L
N
E
34
21
MTL761ac
MTL755ac
Receiver
Fig. 6
L
N
E
MTL755ac
3V
3V
MTL760ac
3
4
10V
10V
1
2
+7V max.
Vout
0V
Fig. 7
EUROPE (EMEA)
Tel: +44 (0)1582 723633
Fax: +44 (0)1582 422283
AMERICAS
Tel: +1 281 571 8065
Fax: +1 281 571 8069
ASIA PACIFIC
Tel: +65 6 487 7887
Fax: +65 6 487 7997
E-mail: enquiry@mtl-inst.com
Web site: www.mtl-inst.com
Jun 2009
Hazardous area
Safe area
BARRIERS
FOR SENSORS
(continued)
MTL761ac
MTL766ac
1
2
3
4
+10V (MTL766)
+6V (MTL761)
0V
6V (MTL761)
10V (MTL766)
MTL764ac
Bridge
3
4
12V
12V
+
Sense
1
2
Optional
MTL761ac
3
4
9V
9V
1
2
Output, mV
Fig. 8
MTL766ac
3
4
12V
12V
Bridge
1
2
+10V
0V
10V
MTL766ac
3
4
12V
12V
3
4
12V
12V
3
4
12V
12V
1
2
Bridge
MTL764ac
Bridge
+
Sense
1
2
MTL764ac
1
2
Output, mV
Fig. 9
bridge: 13.0V
bridges: 9.7V
bridges: 7.7V
bridges: 6.4V
MTL766Pac
3
4
12V
12V
EUROPE (EMEA)
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Fax: +44 (0)1582 422283
AMERICAS
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Fax: +1 281 571 8069
ASIA PACIFIC
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Fax: +65 6 487 7997
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Web site: www.mtl-inst.com
supply
+10V
10V
0V
350
Bridge
MTL761Pac
3
4
9V
9V
3
4
9V
9V
350
Bridge
350
Bridge
1
2
+
Sense
MTL761Pac
1
2
Output, mV
Fig. 10
1
2
MTL758+
3
4
7.5V
7.5V
1
2
MTL761ac
Gas detector
3
4
9V
9V
1
2
+6V
0V
Output
Fig. 11
Jun 2009
Hazardous area
Safe area
BARRIERS FOR
TRANSMITTERS AND
SWITCHES
ANALOGUE INPUTS, HIGH LEVEL
2-wire 4/20mA transmitters
If several transmitters are to be operated from a common dc supply,
and this can be closely regulated (at 26V max), the MTL787S+ now
beats the previously recommended MTL788+ by nearly half a volt,
providing up to 12.9V at 20mA for a transmitter and its lines, as well
as the usual 5V for the load, Fig. 12. Its return channel is more
tolerant of errors during installation and fault finding, and it is safe
with cables of much higher inductance. If the load requirement can
be reduced, the voltage available for the transmitter will be greater.
3
4
28V
Diode
+26V max.
15V
1
2
4/20mA
250
0V
Fig. 12
MTL788R+
3
4
28V
10V
+26V max.
15V
1
2
4/20mA
0V
Fig. 13
The voltage available for the transmitter and its lines can be increased
by converting the return current into a 15V signal before it passes
through an MTL788+ barrier. The MTL788R+ contains a 250
precision resistor for this purpose and makes 14.2V available, Fig.
13.
MTL702+
3
4
25V
E
+35V max.
15V
1
2
4/20/mA
250
0V
Fig. 14
Negative
MTL787S+
MTL787SP+
3
4
MTL706+
28V
E
+35V max.
15V
1
2
4/20/mA
250
0V
Fig. 15
IIB
3
4
28V MTL707P+*
1
Diode
2
15V
+35V max.
15V
4/20mA
0V
Fig. 16
* CENELEC gas group IIB (C & D N. America)
MTL722P+
18V dc
systems
3
4
22V
Earth
1
2
+18V
0V
Fig. 17
EUROPE (EMEA)
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Fax: +44 (0)1582 422283
AMERICAS
Tel: +1 281 571 8065
Fax: +1 281 571 8069
ASIA PACIFIC
Tel: +65 6 487 7887
Fax: +65 6 487 7997
E-mail: enquiry@mtl-inst.com
Web site: www.mtl-inst.com
Jun 2009
Hazardous area
Safe area
For switch-status transfer, Fig. 18, the MTL707+ is preferred for two
reasons. First, the circuit fails safe if there is an earth fault on either line
ie the safe-area load de-energises. Second, the MTL707+ accepts up
to 35V from poorly regulated power supplies without blowing its fuse:
if the supply is well regulated, the MTL787S+ can be used, see Fig. 19.
Fig. 18
3
4
MTL707+
3
4
+35V max.
Logic signal
1
2
28V
Diode
0V
MTL787S+
28V
Diode
+26V max.
Logic signal
1
2
Fig. 19
0V
MTL710P+
3
4
8V dc
systems
10V
Earth
1
2
+8V
0V
Fig. 20
MTL715P+
3
4
12V dc
systems
15V
Earth
1
2
+12V
0V
Fig. 21
Hazardous area
Safe area
BARRIERS FOR
CONTROL ELEMENTS
ANALOGUE OUTPUTS
Controller outputs 4 to 20mA
In most cases the output current of a controller flows directly to its 0V
rail and the rail can be earthed at the busbar, Fig.22. Occasionally the
output circuit may be fully floating. In either event the 1-channel
MTL728+ or half an MTL779+ provides the solution. Overvolt
protection is not required, since current limiting in the controller protects
the fuse in the barrier. The voltage drop introduced by the barrier is
6.8V at 20mA.
I/P
3
4
28V
E
MTL728+
MTL728P+
MTL729P+ 4/20mA
1
2
0V rail
Fig. 22
EUROPE (EMEA)
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I/P
3
4
Fig. 23
28V
Diode
MTL787S+
MTL787SP+4/20mA
1
2
0V rail
Controller
Jun 2009
Hazardous area
Safe area
MTL787S+
MTL787SP+
3
4
I/P
1
2
28V
Diode
4/20mA
Monitor
0V rail
Fig. 24
Controller
MTL707P+ * 4/20mA
28V
Diode
3
4
I/P
1
2
0V rail
Fig. 25
Controller
CENELEC gas group IIB (C & D N. America)
3
4
MTL728+
MTL728P+
MTL729P+*
1
2
+26.6Vmax (MTL728+)
+26V max (MTL728P+)
+26Vmax (MTL729P+)
0V
Fig. 26
MTL708+
3
4
28V
Earth
1
2
+35V max
0V
Fig. 27
MTL787S+
MTL787SP+
MTL707+
MTL707P+ *
3
4
28V
Diode
1
2
Fig. 28
+26.6Vmax (MTL787S+)
+26.5Vmax (MTL787SP+)
+35V max (MTL707+)
+35Vmax (MTL707P+)
0V
Fieldbus applications
The MTL791 (Fig.29) is a 2-channel barrier designed specifically for
31.25kbit/s fieldbus applications. Used with a suitable floating
fieldbus power supply of up to 20V (such as that provided by the
MTL5995 unit) it extends the range of fieldbus applications into
hazardous areas. It is provided with an internal integral safe-area
terminator*.
MTL791
T
EUROPE (EMEA)
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AMERICAS
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Web site: www.mtl-inst.com
Fieldbus devices
3
4
+11V
11V
1 +
2 Fieldbus devices
Fieldbus
power
supply
Fig. 29
Jun 2009
TO ORDER,
State the part number (bold) and any part description shown below.
Enclosures
MT2
MT5
MT12
MT20N
Enclosure
Enclosure
Enclosure
Enclosure
for
for
for
for
2 barriers
5 barriers
12 barriers
20 barriers
Literature
Barrier accessories
EBB7
ERL7
ETM7
ERB7
THR2
IMB7
SMB7
SMC7
TAG7
TGL7
TGS7
TQS7
ISL3
DRK700
Torque spanner
'Take care' intrinsic safety label, adhesive back,
metal
Take care intrinsic safety label, adhesive front,
plastic
DIN Rail mounting kit
MK2
MK5
MK12
MK20
Mounting
Mounting
Mounting
Mounting
ISL7
kit
kit
kit
kit
for
for
for
for
INM700
AN9007
CD70...
2 barriers
5 barriers
12 barriers
20 barriers
EUROPE (EMEA)
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Fax: +44 (0)1582 422283
AMERICAS
Tel: +1 281 571 8065
Fax: +1 281 571 8069
ASIA PACIFIC
Tel: +65 6 487 7887
Fax: +65 6 487 7997
E-mail: enquiry@mtl-inst.com
Web site: www.mtl-inst.com
Jun 2009