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Series
MTL7706/7787 Zener Barrier
Intrinsically Safe Barriers for Hazardous Locations
0.50%
Full Span Accuracy, 4-20 Ma Signal
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The MTL7706/7787
is an intrinsically safe
(IS) shunt-diode barrier that can be used to communicate with and provide
isolations for certain Dwyer® transmitters approved for use in hazardous
areas. These barriers limit the amount of energy allowed to pass into the
hazardous area, which inhibit ignition in flammable atmospheres.
Compatible Models: 637, 638, 639, 608, 2200 |
FEATURES:
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Transmitter
Voltage: 16.2 V at 20 ma with 250Ω Load
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Safe Area Output:
4 to 20 ma
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Load Resistance
0 to 500Ω
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Power Requirements:
20 to 35 VDC w.r.t. earth.
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Temperature Limits:
-4 to 140°F
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LED Indication:
Green: Power Indication
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Safety Description:
28 μ V, 300Ω. 93 ma
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Compatible Models: 637, 638, 639, 608,
2200 |
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MTL Zener Barrier |
Approval |
Dwyer Series |
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MTL7706 |
FM for Class I, II, II; Div. 1 Groups C, D, F, G
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638 |
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MTL7706 |
UL for Class I, II, III; Div. 1 & 2 Groups C, D, E,
F, G |
639 |
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MTL7706 |
FM for Class I, II, III; Div. 1 Groups B, C, D, E,
F, G |
637 |
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MTL7706 |
FM for Class I, II, III; Div. 1 Groups A, B, C, D,
E, F, G |
608 |
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MTL7787 |
FM for Class I, II, III; Div. 1 Groups A, B, C, D,
E, F, G |
2200 |
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MTL7706 |
FM |
| Group |
μF |
mH |
| A & B |
0.083 |
4.2 |
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BASEEFA (ATEX0) |
| Group |
μF |
mH |
| IIC |
0.083 |
4.2 |
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MTL7787 |
FM |
| Group |
μF |
mH |
| A & B |
0.083 |
4.2 |
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BASEEFA (ATEX0) |
| Group |
μF |
mH |
| IIC |
0.083 |
4.2 |
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Region (Authority)
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Standard |
Approved For |
Certificate/file no.
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USA (FM) |
3600, 3610 entity 3611, 3810 |
AIS/I,II,III/1/Entity ABCDEFG-SCI-942; NI/I/@/ABCD/T4
[I/0] AEx[ia]IIC-SCI-942 Entity; NI/1/2/IIC/T4; Ta=140°F (60°C)
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3010737 |
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Canada (CSA) |
CAN/CSA E60070, UL698, UL913, UL1604, IEC60079,
C22.2 |
Class I, Div.2, Gps A, B, C, D; Ex nA [iA] IIC T4
Class I, Xone 2, Aex nA IIC T4 |
1345550 |
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UK (BASEEFA) |
EN 50014, EN 50020 |
EEx ia IIC |
BAS01ATEX7217 |
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UK (BASEEFA) Systems |
EN 50039 |
EEx ia IIC |
Ex01E2219 |
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A Little Bit About Using Zener Barriers and Galvanic
Isolators |
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The MTL5041/5045 Galvanic
Isolators provide
total intrinsically safe isolation for communication with Dwyer® pressure
transmitters approved for location in hazardous areas. Galvanic
isolation eliminates the need for a high integrity earth ground required
when using shunt diode type safety barriers. DIN rail mounting and
plug-in signal and power connectors simplify installation and maintenance.
Compatible Models:
637, 638, 639, 608, 2200, 2900
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The
MTL7706/7787 is
an intrinsically safe (IS) shunt-diode barrier that can be used to
communicate with and provide isolations for certain Dwyer® transmitters
approved for use in hazardous areas. These barriers limit the amount of
energy allowed to pass into the hazardous area, which inhibit ignition in
flammable atmospheres. Requires high integrity earth ground
Compatible Models: 637,
638, 639, 608, 2200
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What is a Good ground resistance value? |
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There is a good deal
of confusion as to what constitutes a good ground and what the ground
resistance value needs to be. Ideally a ground should be of zero ohms
resistance.
There is not one standard ground
resistance threshold that is recognized by all agencies. However, the NFPA
and IEEE have recommended a ground resistance value of 5.0 ohms or less.
The NEC has stated to Make sure
that system impedance to ground is less than 25 ohms specified in NEC
250.56. In facilities with sensitive equipment it should be 5.0 ohms or
less.
The goal in ground resistance is to
achieve the lowest ground resistance value possible that makes sense
economically and physically.
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