The MTT MS3921 Chassis-mounting PT Transmitter converts the AC voltage signal from a potential (voltage) transformer into a standard isolated DC output, giving switchgear and motor control panels a clean, ground-loop-free way to read line voltage into a PLC, indicator, or recorder. True-RMS operation keeps the reading accurate even when the monitored voltage waveform is distorted by non-linear loads elsewhere on the system, rather than assuming a clean sine wave.
Built in the compact chassis-mount format shared with the rest of the MS39-series for high-density installations on MTT’s RC3900 chassis platform, the MS3921 accepts standard PT secondary voltages such as 100V, 110V, or 300V AC and can withstand momentary overvoltage without damage. Dual output combinations of voltage and current are available to match the receiving equipment, front-accessible trimmers allow zero and span adjustment, and isolation between input, both outputs, and power supply keeps the transmitted signal free of noise and interference.
| Input Range | 0-100V AC, 0-110V AC, 0-300V AC, or custom (50/60Hz) |
| Input Resistance | 1MΩ min. |
| Max Input | 120% continuous; 1.5x rated input instantaneous (5s max) |
| Crest Factor | 3 max |
| Output Options | 1-5V DC, 0-5V DC, 0-10V DC, ±5V DC, ±10V DC, or 1-5V DC/4-20mA DC combinations (dual isolated outputs) |
| Output Load | 2mA max (voltage); 300Ω max (current) |
| Adjustment | ±2% of span, zero and span, via front trimmer |
| Accuracy | ±0.25% F.S. (25°C±5°C); ±0.2% span per 10°C temperature effect |
| Power Sensitivity | ±0.1% of span max. at 10% variance |
| Response Time | 0.4s max (0-90%, 100% step) |
| CMRR | 100dB min. (500V AC, 50/60Hz) |
| Isolation | Mutual isolation across input, outputs, and power; 100MΩ min. insulation resistance @500V DC; 1500V AC dielectric strength (input/other), 500V AC (outputs/power, 1 min) |
| Surge Withstand | Per ANSI/IEEE C37.90.1-1989 |
| Power Supply | 24V DC ±10%, 55mA max; 300mA fuse standard |
| Dimensions | W19.5 x H53 x D84mm |
| Weight | Approx. 70g |
| Housing | ABS resin (UL94V-0); glass-fabric epoxy PCB (CEM-3) |
| Mounting | Chassis mount, RC3900 mounting base required |
| Operating Conditions | 0-55°C, 90% RH max non-condensing |
| Storage Temperature | -10 to 60°C |
| Additional Features | Anti-humidity PCB coating (HumiSeal 1A27NS); self pop-up wiring screws |
Frequently Asked Questions
What is the MTT MS3921 used for?
It converts the AC voltage signal from a potential (voltage) transformer into a standard isolated DC output, giving switchgear and motor control panels a clean, ground-loop-free way to read line voltage into a PLC, indicator, or recorder.
Does it handle distorted voltage waveforms?
Yes, true-RMS operation keeps the reading accurate even when the monitored voltage waveform is distorted by non-linear loads elsewhere on the system, rather than assuming a clean sine wave.
What PT secondary voltages does it accept?
Standard PT secondary voltages such as 100V, 110V, or 300V AC. Tell us your PT’s secondary rating and we can confirm the configuration.
Can it withstand a voltage surge on the monitored line?
Yes, the MS3921 can withstand momentary overvoltage without damage, which matters since PT secondaries can see transient surges during switching events.
How do I know if the MS3921 is right for my application?
If you need to transmit a PT’s voltage reading into a PLC or panel meter, with true-RMS accuracy and surge tolerance, the MS3921 on an RC3900 base covers that. Send us your PT’s secondary rating and the output signal you need and we’ll confirm before you order.
Download MTT MS3921 Chassis-mounting PT Transmitter information here
Datasheet: MTT_MS3921_Datasheet
