The Crouzet em4 is a nano-PLC telecontroller that packs PLC functionality, a cellular modem, alarm management, data logging, and an LCD operator display into a single 124.6 × 90 × 60.6 mm DIN-rail module. It was designed for the specific problem of monitoring and controlling equipment in locations where running Ethernet cable is impossible or cost-prohibitive: remote pump stations, water tanks, wells, HVAC rooftops, and distributed infrastructure. A built-in GSM/3G modem is the primary communication channel, with SMS, email, and FTP replacing traditional SCADA polling.

How does the em4 handle remote monitoring and alarm notification?

The em4 Alert and Remote variants include a built-in GSM/3G modem with a standard SIM card slot. When a monitored parameter crosses a threshold — a tank level too high, a pump drawing overcurrent, a temperature out of range — the em4 sends SMS text messages to pre-configured phone numbers (up to 20 recipients) and email alerts with the triggering condition and timestamp. It can also receive SMS commands: an operator texts a code to the em4's SIM number to acknowledge an alarm, change a setpoint, or toggle an output. Data logs are stored locally and sent as .CSV files via email or FTP on a schedule or on demand.

Can the em4 be programmed and updated remotely?

Yes. The em4 Soft programming software (free, function block diagram and sequential function chart) runs on a Windows PC and connects locally via USB. Once deployed, the full PLC application can be updated remotely: upload the new program to an FTP server from the programming PC, then trigger the em4 to download and install it over the cellular connection. This eliminates site visits for program changes — critical when em4 units are deployed across dozens of geographically dispersed locations.

What I/O and expansion options are available?

The base unit provides 16 digital inputs — 4 of which are high-speed counters (up to 60 kHz) — and 12 are configurable as analog inputs accepting 0–10 V, 0–24 V DC, 4–20 mA, or direct sensor connections (NTC thermistors, LDR, pressure, flow, humidity, level sensors). Outputs include 8 relays (6 × 8 A, 2 × 6 A) and 2 solid-state outputs for PWM or 0–10 V analog control. Two expansion slots accept E10A analog or E10R digital I/O modules, expanding total I/O to 46 points. The em4 Ethernet variant adds Modbus TCP/IP for integration with local networks where available.

Frequently Asked Questions

What cellular networks does the em4 Alert support?

The em4 Alert 3G (88981123) operates on GSM 850/900/1800/1900 MHz bands with 3G data. A standard SIM card (not included) is required — the same type used in mobile phones. Data consumption is low since SMS and CSV file transfers use minimal bandwidth. Check local 2G/3G network availability, as some regions are sunsetting 2G and 3G networks in favor of 4G/5G. The earlier 2G-only model (88981113) is now obsolete in most markets.

How does the em4 compare to a traditional RTU?

The em4 bridges the gap between a smart RTU and a compact PLC. Unlike a traditional RTU that typically needs an external modem and separate programming tools, the em4 integrates the cellular modem, I/O, programming environment, and operator display in one device. It lacks some RTU-specific protocols like DNP3 and IEC 60870-5-101/104, relying instead on SMS, email, FTP, and Modbus for data exchange. For applications that need standard telecontrol protocols, a dedicated RTU may be more appropriate. For applications that prioritize rapid deployment and simple SMS-based remote control, the em4 is the leaner choice.