The MTT MS3705 is a slim plug-in alarm setter that watches a DC current or voltage signal and switches two independent, isolated relay outputs when the signal crosses a set point. Each set point is dialed in on a front-accessible rotary switch as a percentage of the input span, so alarm thresholds can be adjusted on site without special tools or a laptop, and built-in hysteresis stops the relay from chattering when the signal sits right at the trip point.
Because the two relay outputs are electrically isolated from the input, from the power supply, and from each other, the MS3705 can drive two independent alarm circuits, such as a low and a high limit, or a local indicator and a remote annunciator, from a single measured signal. Like the rest of the plug-in transmitter range, it clips into its own socket base so the unit can be swapped for calibration or replacement in seconds 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 | 4-20mA DC, 0-20mA DC, 0-1V DC, 0-5V DC, 0-10V DC, or 1-5V DC |
| Input Resistance | 1MΩ minimum (voltage, with power); 250Ω (current) |
| Allowable Input | 30V DC max. (voltage); 40mA DC max. (current) |
| Alarm Setpoint Adjustment | Front-accessible rotary switch, 0-99% of input span in 1% increments (factory default 50%) |
| Setpoint Accuracy | ±0.5% of span |
| Hysteresis | 1.0%±0.3% of span |
| Output | Two independent, isolated Form C relay contacts |
| Relay Rating | 5A at 125V AC or 5A at 30V DC (max. 250V AC / 30V DC, 5A NO / 3A NC) |
| Relay Electrical Life | 50,000 cycles (AC); 100,000 cycles (DC) |
| Power Supply | 100-240V AC (85-264V AC, 47-63Hz, 6.5VA max), 24V DC ±10% (2.0W max), or 100-240V DC (8.4W max) |
| Response Time | 150ms maximum (0-90%) |
| Temperature Effect | ±0.15% of span per 10°C change |
| Power Sensitivity | ±0.1% of span |
| Insulation Resistance | 100MΩ minimum at 500V DC |
| Dimensions (W x H x D) | 29mm x 86mm x 125mm |
| Weight | Main unit 130g; 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 |
| Standards | EMC Directive 2014/30/EU (EN61326-1:2013); Low Voltage Directive 2014/35/EU (IEC61010-1, EN61010-1:2010); Installation Category II, Pollution Degree 2 |
Frequently Asked Questions
What is the MTT MS3705 used for?
It monitors a DC current or voltage process signal and switches relay contacts when the signal crosses a set point, giving a local alarm or interlock signal without needing a separate PLC or controller to do the comparison.
How is the alarm set point adjusted?
Using a front-accessible rotary switch on the unit, from 0-99% of the input span in 1% steps, with a factory default of 50%. No separate programming tool is needed.
Are both relay outputs triggered by the same set point?
The two Form C relay outputs are independent and isolated from each other, so each can be wired to a different alarm circuit even though they respond to the same monitored input.
What’s the difference between the MS3705 and the MS3705HA/MS3705HB?
These are variants within the MS3705 alarm setter family with different setpoint ranges or hysteresis behaviour. Tell us your process signal and the alarm trip levels you need, and we can confirm the right variant.
Can the MS3705 replace an existing alarm relay unit?
In most cases yes, as long as the input signal type and range match. Send us the model on the old unit’s label, or your input signal and the relay rating you need, and we’ll check compatibility before you order.
Download MTT MS3705 Slim Plug-In Alarm Setter information here
Spec Sheet: MTT MS3705 Spec Sheet
Manual: MTT MS3705 Manual
