The MTT MS3707H is a slim plug-in distributor built for 2-wire HART transmitters, powering the transmitter loop and reproducing its 4-20mA signal as a galvanically isolated output while passing the HART digital communication signal through undistorted. That means a HART configuration tool can still talk to the field transmitter through the isolator, while the receiving control system sees a clean, isolated 4-20mA signal.
Front-accessible zero and span trimmers make on-site calibration quick, and like the rest of the plug-in transmitter range, the MS3707H clips into its own socket base so the unit can be swapped for calibration or replacement in seconds without disturbing the field wiring. Flexible AC or DC power plus wall or DIN rail mounting make it easy to fit into an existing panel, making it a straightforward way to add loop isolation to a HART-enabled instrument without losing HART communication.
| Input | 4-20mA DC from 2-wire HART transmitters |
| Input Resistance | 250Ω |
| Transmitter Power Supply | 25V typical at 0% input; 18V typical at 100% input |
| HART Pass-Through | Bidirectional, 500Hz-10kHz bandwidth (max. attenuation -10dB); approx. -3dB gain at 1-3kHz; requires 250Ω load for optimal performance |
| Output | 4-20mA DC, isolated |
| Output Load | 600Ω max. (250Ω when using HART communication) |
| Zero & Span Adjustment | ±5% of span each, front-accessible |
| Isolation | 4-way isolation between input, output, power, and ground |
| Power Supply | 100-240V AC (85-264V AC, 47-63Hz, 7.7VA max), 24V DC ±10% (2.2W max), or 100-240V DC (2.9W max) |
| Accuracy | Better than ±0.1% of span (at 25°C±5°C) |
| Temperature Effect | ±0.2% of span per 10°C change |
| Response Time | 500ms maximum (0-90%) |
| CMRR | Minimum 100dB |
| Insulation Resistance | 100MΩ minimum at 500V DC |
| Dielectric Strength | 2000V AC for one minute |
| Dimensions (W x H x D) | 29mm x 86mm x 125mm |
| Weight | Main unit 120g; socket 80g |
| Mounting | Wall or DIN rail mounting, plug-in socket base |
| Terminals | M3.5 screw terminals |
| Operating Temperature | -5 to 55°C ambient (storage: -10 to 60°C) |
| Operating Humidity | 5-90% RH, non-condensing |
Frequently Asked Questions
What is the MTT MS3707H used for?
It’s a distributor built for 2-wire HART transmitters: it powers the transmitter loop, reproduces the 4-20mA signal as an isolated output, and passes the HART digital signal through so a configuration tool can still talk to the transmitter.
Will HART communication still work through the isolator?
Yes — the MS3707H passes HART signals through bidirectionally (500Hz-10kHz) with minimal attenuation, so a HART handheld or host system can still configure and read the field transmitter as normal.
What’s the difference between the MS3707H and the standard MS3707?
The standard MS3707 is a general-purpose distributor for 2-wire 4-20mA transmitters. The MS3707H is built specifically to pass HART communication through undistorted while still providing loop power and isolation, which the standard MS3707 does not guarantee.
Does the output load affect HART communication through the MS3707H?
Yes — the output supports up to 600Ω normally, but for reliable HART communication a 250Ω load is recommended, which is the standard requirement for HART signalling.
How do I know if I need the MS3707H instead of a standard isolator?
If your field transmitter is HART-enabled and you need to keep using HART tools for configuration or diagnostics after adding isolation, the MS3707H is the right choice. Send us your transmitter details and we can confirm compatibility.
Download MTT MS3707H Slim Plug-In HART Isolator information here
Spec Sheet: MTT MS3707H Spec Sheet
Manual: MTT MS3707H Manual
