Series-MTL7706-7787

Supported Applications

The Dwyer Series MTL7706/7787 consists of intrinsically safe shunt-diode barriers designed to communicate with and provide isolation for specific Dwyer® transmitters approved for use in hazardous areas. These devices limit the amount of energy allowed to pass into the hazardous area, inhibiting ignition in flammable atmospheres.

According to series documentation, these Zener barriers are compatible with the following Dwyer transmitter models:

• Series 637
• Series 608
• SBLTX Series
• PBLTX Series
• IS626 Series

Operating Conditions & Performance

The barriers operate within an ambient temperature range of -4 to 140°F (-20 to 60°C) and a storage temperature range of -40 to 176°F (-40 to 80°C). Humidity ratings are specified as 5 to 95% RH. The electrical performance includes an accuracy of ±2 µA under all conditions, with a load resistance capability from 0 to 500 Ω.

Power supply requirements are 20-35 VDC w.r.t. earth. The output signal is specified as 4-20 mA. Safety parameters for the system include a safety description of 28 µV, 300 Ω, and 93 mA.

Configuration Options

The series includes two primary barrier models with distinct electrical characteristics:

• MTL7706: Zener barrier configured for FM Groups A & B (Capacitance 0.083 µF, Inductance 4.2 mH) and BASEEFA Group IIC (Capacitance 0.083 µF, Inductance 4.2 mH).
• MTL7787: Zener barrier configured for FM Groups A & B (Capacitance 0.083 µF, Inductance 3.05 mH) and BASEEFA Group IIC (Capacitance 0.083 µF, Inductance 3.05 mH).

Physical dimensions for the barriers are a width of 4-5/32 [105.57], height of 3-35/64 [90.09], and depth of 1/2 [12.70]. The unit weight is 4.9 oz (140 g). Electrical terminals accommodate up to 2.5 mm² stranded or single-core wire.

Mounting accessories available for the series include:

• A-360: Aluminum DIN rail, 1 m length.

Key Product Differences

The MTL7706 and MTL7787 models differ primarily in their approved hazardous area classifications and internal electrical parameters (inductance). The MTL7706 is listed for UL Class I, Div. 1 Groups A, B, C, D; CL II, Div. 1 Groups E, F, G; and CL III Div. 1. It also holds FM approval for Class I, II, III; Div. 1 Groups B, C, D, E, F, G (Model 637) and Groups A through G (Model 608).

The MTL7787 is identified as a Zener barrier in the model chart but specific hazardous area group approvals for this variant are not detailed separately from the general series capabilities in the provided data. Both models carry CE, CSA, Ex, FM Approved, and UL Listed certifications.