VM-4TC Veichi VM-4TC Expansion module: thermocouple measurement, compatible with the VM series.

VM-4TC is a VM-series temperature input module with 4 channels for thermocouples. You connect thermocouples directly — the module processes the thermocouple signal and converts it to temperature. It works inside a VM node on a VM-RTU-ECT or VM-RTU-PN coupler.

Typical applications:

• Temperature control in furnaces, dryers and heating chambers.
• Injection-molding machines and extruders — screw and nozzle heating zones.
• High-temperature processes where Pt100 no longer covers the range.

Note: the module plugs into a VM node on a VM-RTU-ECT or VM-RTU-PN coupler — it does not work on its own or directly off a CPU. Thermocouples cover a much wider temperature range than Pt100, but at moderate temperatures Pt100 is more accurate — for those take VM-4PT. If the temperature is already converted to a standard 4–20 mA, VM-4AD is enough.

Veichi VM — distributed remote I/O modules

VM is not a standalone controller and not a local right-side CPU expansion, but a remote-I/O family. A VM node is built like this: you take a bus coupler — VM-RTU-ECT for EtherCAT or VM-RTU-PN for Profinet — clip up to 16 VM I/O modules onto it, and bring the whole node onto the fieldbus to a master — for example VC5/VH500/VH600 or a third-party EtherCAT/Profinet master. To the master the node looks like a single remote I/O station. The module set covers transistor digital outputs (NPN and PNP), digital inputs, analog (in and out), temperature modules for Pt100 and thermocouples.

The key trait of VM versus the VC series is that its discrete outputs are transistor type, NPN or PNP. That means fast 24 V DC switching with no contact wear: solenoids, pneumatic valves, VFD inputs and relays. There are no relay outputs in the VM digital modules — for a dry contact or mixed AC/DC load, look at the relay modules in the VC line.

How to pick a VM module for your task

• Bus coupler (mandatory): VM-RTU-ECT (EtherCAT) or VM-RTU-PN (Profinet) — the I/O modules do not work without it. Choose by the master's protocol.
• Digital outputs: VM-0008ETN / VM-0008ETP (8 outputs) and VM-0016ETN / VM-0016ETP (16 outputs). The trailing N is NPN (common positive), P is PNP (common negative). Choose by the logic of the sensors and actuators on the machine.
• Digital inputs: VM-0800END (8 inputs) and VM-1600END (16 inputs) — purely for buttons, limit switches, proximity sensors.
• Mixed I/O: VM-0808ETN and VM-0808ETP — 8 inputs plus 8 transistor outputs in one housing, handy for a compact node.
• Analog and temperature: VM-4AD (4 analog inputs), VM-4DA (4 analog outputs), VM-4PT (4 Pt100 channels), VM-4TC (4 thermocouples).

VM digital modules — comparison

In practice I suggest counting the real points on the schematic with a small margin first, then picking the module count and type — there is no point paying for spare channels. One coupler carries up to 16 modules, so a large node is often covered by a single station.

What to keep in mind with VM

• This is remote I/O, not a local CPU expansion. The module itself (VM-0008ETN and so on) does NOT clip directly to a CPU and does not work on its own — it requires a VM-RTU-ECT or VM-RTU-PN coupler, which brings the node onto the fieldbus to a master.
• If you need a true local right-side CPU expansion, those are different families: look at the VC or VH-R modules next to the Veichi PLCs.
• If you need a relay output or a mixed AC/DC load, the transistor VM modules will not do — take the relay modules in the VC series.
• Considering another ecosystem — compare with Delta or Fatek.

Our experience with VM

VM gets picked when the I/O has to be moved away from the CPU and gathered into a remote station on the bus — for example spreading I/O across a large machine and tying it all into a single EtherCAT or Profinet node. The most common question is the NPN/PNP difference — here go by the logic of the sensors you already have, so you don't add intermediate relays. On the same machine, Veichi VFDs and operator panels often go alongside.