The MTT MS3721 is a slim plug-in PT transmitter that reads the AC output of a potential transformer, calculates its true RMS value, and converts it into a standard DC signal for displays, controllers, and data acquisition systems. It gives a safe, low-level way to monitor higher system voltages, since the PT itself does the step-down and the MS3721 handles the conversion to a usable DC output without exposing downstream equipment to the actual line voltage.
Multiple input voltage ranges are available to match common PT secondaries, and current or voltage output options let it fit the receiving equipment, with a second isolated output for feeding an independent monitoring or alarm system at the same time. Like the rest of the plug-in transmitter series, the MS3721 clips into its own socket base for fast swap-out during calibration or maintenance without disturbing the field wiring, and flexible AC or DC power plus wall or DIN rail mounting make it easy to fit into an existing panel.
| Input Range | 0-110V AC, 0-150V AC, or 0-300V AC, 50/60Hz |
| Input Resistance | 1MΩ min. |
| Crest Factor | 3 max. |
| Output | 0-20mA or 4-20mA DC current; 10mV to 20V DC voltage; single or dual isolated output |
| Accuracy | Better than ±0.25% of span (10%+ input) |
| Temperature Effect | ±0.2% of span per 10°C change |
| Response Time | 400ms max. (0-90%) |
| Isolation | 4-way isolation between input, output 1, output 2, and power |
| Insulation Resistance | 100MΩ min. at 500V DC |
| Dielectric Strength | 2000V AC for 1 minute |
| Power Supply | 100-240V AC, 24V DC, or 100-240V DC |
| Power Consumption | 4.5-6.0VA/W depending on configuration |
| Dimensions | W29 × H86 × D125mm |
| Weight | 120g max. (main unit), plus 80g max. socket |
| Mounting | Wall or DIN rail mounting |
| Terminals | M3.5 screw terminals, 0.8-1.0 Nm torque |
| Operating Temperature | -5 to 55°C |
| Operating Humidity | 5 to 90% RH, non-condensing |
Frequently Asked Questions
What is the MTT MS3721 used for?
It reads the AC output of a potential transformer (PT), calculates the true RMS voltage, and converts it into a standard DC signal for your display, controller, or data acquisition system — a safe way to bring a high system voltage reading into a monitoring system through the PT’s low-voltage secondary.
What PT input ranges does the MS3721 support?
It covers 0-110V AC, 0-150V AC, or 0-300V AC secondaries. Tell us your PT’s secondary voltage rating and we can confirm the right input range at order.
What’s the difference between the MS3721 (PT transmitter) and the MS3720 (CT transmitter)?
The MS3720 reads current from a current transformer. The MS3721 reads voltage from a potential transformer. If you’re measuring system voltage rather than current, the MS3721 is the right model.
Can the MS3721 provide two separate outputs?
Yes — a second isolated output is available, so the voltage reading can feed a controller and a separate monitoring or alarm system at the same time.
How do I know if the MS3721 is the right model for my application?
Send us your PT’s secondary voltage rating and the output signal your receiving equipment expects, and we can confirm before you order.
Download MTT MS3721 Slim Plug-In PT Transmitter (RMS Calculation) information here
Spec Sheet: SpecSheet1_MS3721_Rev300_E.pdf
Manual: Manual1_MS3721_Rev170_E.pdf
