Quick guide – system components:
- 📡 Master – collects data and sends it to IWMAC
- 🔁 Repeater – extends coverage (0–4 per store)
- 🌡️ Sensor node – measures temperature and humidity (10–80 per store)
- 🔍 Probe sensor – handheld for spot checks
1. Component overview
The system to be installed consists of the following components:
- Sensor nodes
- Sensors (1 sensor per sensor node)
- 1–4 repeaters
- 1 probe sensor (not all installations)
- 1 master
- 1 Ethernet cable (only where the master node is to be connected directly to the internet)
- Metal discs for attaching sensor nodes to insulating surfaces
- User manual
2. System description
The system consists of four types of nodes: a master, optional repeaters, a number of sensor nodes, and a handheld sensor node/probe sensor. All units have embedded magnets that make installation very straightforward. A metal disc with double-sided tape is available where there is no magnetic surface.
2.1.1 Master
The master collects measurement data from the sensor nodes and forwards it to IWMAC's server. The master can communicate directly with sensor nodes or via a repeater. It is available in two versions: one that connects to a local PC (RS232, 9-pin D-sub), and one that delivers data directly to the internet via a wired network connection (RJ45).
2.1.2 Repeater
Repeaters extend the system's coverage area by relaying measurement data from sensor nodes to the master. A repeater always communicates with the master and with sensor nodes that wish to use it. Repeaters have the same physical appearance as sensor nodes and are distinguished by their external power adapter. They normally run on mains power (230V) but switch to an internal battery backup during power outages.
2.1.3 Sensor node
Sensor nodes measure temperature and optionally relative humidity (RH) using external sensors. They are placed in or near refrigeration/freezer units or wherever climate monitoring is needed. Selection of master/repeater is automatic, and the node switches to a new communication path if conditions deteriorate.
Sensor nodes are available in three variants: with 1, 2 or 4 sensor inputs.
There are 6 variants of external sensors:
- Short temperature sensor
- Temperature sensor with 1.5 m cable
- Temperature sensor with 3 m cable
- Temperature sensor with 6 m cable
- Temperature sensor for washing machine
- Relative humidity sensor (RH sensor)
Sensors connect to the RJ-11 connector(s) on the sensor node.
2.1.4 Probe sensor
The probe sensor is a handheld variant of the sensor node used to measure the temperature of incoming goods and/or to conduct spot checks where no fixed temperature sensor is installed (for example, measuring the internal temperature of hot food).
2.2 Coverage and range
Under ideal conditions (line of sight, little interference, good antenna) the range between two units exceeds one kilometre. In a real installation, range is always reduced by walls, shelves, goods, etc. Range can be extended by positioning the master node's antenna as centrally in the store as possible.
2.3 Mounting mechanism
All nodes are equipped with 4 magnets on the lid. The magnets are covered by a round friction tape that prevents the unit from sliding. Where there is no magnetic surface (e.g. glass walls), a magnetic metal disc (Ø 40 mm) is first attached to the wall with double-sided tape.
2.4 Installation mode
Installation mode is activated by unplugging and replugging the master node's power cable. All sensor nodes will then flash their LEDs to indicate connection quality:
- Green flash: Good connection (margin ≥ 20 dB)
- Green/red flash: Marginal connection (10–20 dB)
- Red flash: Unstable connection (0–10 dB)
- No flash: No radio connection
Installation mode lasts for 30 minutes. It can also be activated on a single sensor node by removing and reinserting the yellow plug.
2.5 LED indicator (sensor nodes and repeaters)
The LED is visible at the antenna entrance on the right side of the unit.
- Sensor node – normal operation: Flashes once per minute. Lights for approx. 1 second each time it transmits data.
- Sensor node – installation mode: Flashes every second (direct to master, no repeater) / 3 times every 4 seconds (direct to master, with repeater in network) / once every 4 seconds (connected to repeater).
- Repeater node: Flashes once every 4 seconds when in contact with master. Short flash = mains not connected. Long flash = power adapter connected.
The LED colour always indicates the quality of the radio connection upward in the network.
2.6 Yellow plug
Sensor nodes and repeaters are supplied with a yellow plug inserted in the RJ-11 connector — the node is then switched off. The yellow plugs should be returned to WNC after installation.
2.7 Activating and deactivating nodes
- Master: Activated by connecting the power supply. Deactivated by disconnecting.
- Repeaters and sensor nodes: Activated by removing the yellow plug (LED lights green for approx. 1 second). Deactivated by inserting the yellow plug (LED lights red for 2–3 seconds).
3. Installation
3.1 Positioning the master and master antenna
Start by positioning the master as centrally as possible within the area to be covered. The included whip antenna with magnetic base should be placed on a metal surface, preferably high up (fewer obstacles near the ceiling). An extension cable can be used for optimal antenna placement.
Master via GPRS: Can be placed anywhere in the store (preferably above ceiling tiles) as long as mains power is accessible.
Power supply: The master must have a reliable power supply — during a power outage, all data is stored locally in the sensor nodes until the master is back online. Ensure the socket is not controlled by a switch.
Master variants:
- Master RS232 – connects to local PC (9-pin D-sub). Powered via the data cable from the PC.
- Master-gateway – delivers data directly via wired network (RJ45). Powered by its own power adapter (230V).
3.2 Deploying sensor nodes
Activate the sensor node by removing the yellow plug and move around the premises while watching the LED. This gives an indication of master coverage and where repeaters may be needed. For stable communication, the LED should flash green from the node's installed position. Signal strength can also be read from a graph on IWMAC's server.
3.3 Adjusting the sensor antenna
Sensor nodes have an antenna wire that can be pulled out through the LED hole. Extending this wire in the air increases range (similar to the antenna on an old portable radio).
3.4 Installing a repeater
If it is not possible to deploy more sensor nodes with good coverage, install a repeater. Position it high up with good coverage of the weakest areas and a good connection to the master. Repeaters require mains power (230V).
3.5 Using the probe sensor
Activate by pressing the button at the top right of the keypad. The unit measures temperature every second and displays it continuously. To record a measurement: enter a product number followed by two presses of the # key. If out of radio coverage, the measurement is stored until coverage is re-established. The unit switches off automatically after 10 minutes without activity.
3.6 Temperature conditions for sensor nodes
Sensor nodes are designed for –35 °C to +40 °C, but for maximum battery life, placement in a range of 0–25 °C is preferred. Avoid mounting sensor nodes between freezers where waste heat is expelled — this significantly reduces battery life. The ideal position in an open freezer is just above the cold zone, with the sensor hanging down into the cold zone.
3.7 Sensor conditions
Short sensors should hang freely without being pinched or forced into position. They must not be placed where they regularly come into contact with goods being placed in or removed from refrigeration units. Long sensor cables must not have sharp bends or be exposed to unnecessary stress. Clips must not be fixed directly against the sensor — this can cause cable breakage over time.
4. Alternative configurations
The simplest configuration has all sensor nodes communicating directly with the radio master. For better radio connections, the master antenna can be positioned in the store area using an extended antenna cable. In many stores, repeater nodes will be used to ensure robust radio connections to all sensor nodes.
Once in operation, sensor nodes automatically switch between communicating directly with the master and via a repeater — depending on current radio conditions. A sensor node is never locked to a specific repeater.
5. Registration and configuration of nodes
All units in the system (sensor nodes, repeaters, handheld and master) are pre-configured when delivered for store installation. It is therefore not necessary to perform configuration during installation of the sensor network.