Square Impact for LoRaWAN

1Introduction

Square Impact measures motion and vibration with a 3D accelerometer and analyses it on the device. When it is knocked or set vibrating, it works out how the energy is spread over frequency bands from 1 to 256 Hz and how much energy there is in total, and reports changes over LoRaWAN rather than a stream of raw data. It can also report its orientation on three axes, gives an indication of the temperature, and scans for Wi-Fi once a day for its position. The sealed, grey housing is IP68 and IK06, 67.2 × 60.4 × 13 mm, for machines, warehouse racking and structures.

The battery is built in (4,000 mAh); battery life depends on the mode and how often it reports.

It works with any LoRaWAN network server (LoRaWAN 1.0.4, class A, OTAA) and reaches up to 10 km in line of sight. What it measures, when it reports and what it sends is decided by an application running inside the sensor, on Sensative’s Virtual Sensing Machine (VSM). This manual describes the application Motion-spectrum R31–R33, which can be configured, and replaced by a newer version, over the air or with NFC. Sensative can also offer alternative VSM applications for the same sensor, which give it a different task; see Which application is in the sensor.

What’s in the box

• Square Impact, with the adhesive already on the back
• The screw mounting frame

The keys (DevEUI and AppKey) come with the delivery information. Screws and cable ties are not included.

Parts of the sensor

2Before you start

A LoRaWAN sensor needs a little more preparation than a sensor that pairs with a hub. Have this ready first:

You need

• A LoRaWAN gateway within range, powered on and online
• An account on a LoRaWAN network server (for example The Things Network, ChirpStack, Loriot or Actility), with the gateway added to it
• The keys for the sensor: its DevEUI and AppKey, from the delivery information. The JoinEUI is the same for all Square sensors: 70B3D52C0001D4C3.
• A phone with NFC, to start the sensor. Most smartphones have it; an iPhone needs an NFC reading app (see Finding the NFC antennas).
• A payload decoder for Sensative VSM sensors in your network server or application (see Decoding the messages)

Choosing the place

• Firmly on the structure: fix the sensor rigidly to the machine, upright or beam whose motion you want to measure, so that it moves with it
• Outdoors and in industry: the housing is IP68 and IK06, for wet, dusty and knocked-about places
• Range: up to 10 km in open line of sight, much less through walls and floors

Finding the NFC antennas

NFC only reaches a couple of centimetres, so lay the phone flat against the sensor, antenna over antenna. You need to know where both antennas are, and the easiest way to find the spot is to move the phone slowly over the right area until the phone signals contact:

• On the sensor: at the lower left of the front, with the logo along the bottom edge.
• On an Android phone (recommended): switch NFC on, and turn on vibration or a sound for NFC in the phone’s settings, so that the phone tells you as soon as it has found the sensor. The antenna is usually on the back, near the top, often close to the camera, but it varies between models: the phone’s manual or the maker’s website shows where it is. If you cannot find it, move the back of the phone slowly over the sensor’s lower left corner until the phone vibrates.
• Take off the phone case: a protective case, especially a thick one or one with metal or a magnet, can make it hard to get NFC contact. Remove it while you work with the sensor.
• Then hold it still: to start a join, keep the phone still over the sensor for about 5 seconds. The vibration only means the phone has found the sensor. Keep the phone where it is until the sensor and the app have finished talking. With the Hugin app this takes a few seconds, because the app first unlocks the sensor through Sensative’s server. If you move away too early, the connection breaks and you have to start again.
• On an iPhone: use an NFC reading app, such as NFC Reader & Scanner from the App Store. Open it and tap its NFC button, so that it shows Ready to Scan, before you touch the sensor. The iPhone’s antenna is at the top edge of the back. Hold that edge against the sensor’s lower left corner and keep it still; when the read succeeds, a web link with the sensor’s serial number opens. The iPhone NFC join guide (PDF) shows each step with pictures.

3Step by step: from box to ready

8 steps. Register the sensor in the network server before you hold the phone to it. Then join it, check the settings, and mount it last.

3

Join the network with NFC

Hold the phone over the lower left corner of the front of Square Impact and keep it still for about 5 seconds: that starts the join (see Finding the NFC antennas, also for iPhone). The phone may show a web link with the sensor’s serial number; you do not need to open it.

Done when: the network server shows the join, usually within two minutes.

If the network is not yet reachable, the sensor tries again once a day, so the join can take up to 24 hours once the network is there. A new NFC touch starts an attempt at once.

6

Install

Choose one way, or combine them:

1. Screws, with the included mounting frame: fix the frame with M4 screws (not included). This gives the most rigid fixing.
2. Adhesive: the adhesive is already on the back. Clean the surface with a 50:50 mixture of isopropyl alcohol and water, so that it is free of dirt and grease, and let it dry. Peel the film off the adhesive and press the sensor firmly in place.
3. Cable ties: through the eyelets. Cable ties can be combined with adhesive for extra hold.

Keep the front reachable for a phone (NFC).

4Using the sensor

The application measures motion and vibration with the accelerometer, analyses it on the device, and reports what has changed. The settings named in bold are listed in the settings table.

Vibration spectrum and energy

When Square Impact detects motion, it measures the accelerometer at a high rate, about 800 times a second, for 2 seconds, and splits the vibration into octave bands at about 1, 2, 4, 8, 16, 32, 64, 128 and 256 Hz. It reports:

• The spectrum: the share of the energy in each band, in per cent. Slow movements, such as a swaying beam, show in the low bands; a running motor or a hard knock in the higher ones. The analysis is simplified to save battery, but gives a fair picture of how the energy is spread.
• The total energy of the measured motion, in (mm/s²)².
• Only changes: the spectrum is sent when the energy or its spread has changed. When the motion stops, a motion report is sent instead of a row of zeros.
• Only while joined: the sensor measures the spectrum only while it is joined to a network, so not during transport or in stock.

When it measures: the Spectrum Reporting Mode

• 1, interval measurement while moving (default): the sensor wakes on motion and repeats the measurement at intervals of about a minute for as long as the motion continues.
• 2, constant measurement while moving: the measurement is repeated about every 2 seconds while the motion continues. This catches more, and uses more battery.
• 3, fixed interval: the sensor measures every Motion Poll Interval (10 minutes by default), whether or not it has been woken by motion. A spectrum is sent only if the total energy is above the Motion Threshold squared.
• 0, wake on motion only: no spectrum is measured; the sensor only reports motion.

The Motion Threshold sets how strong a movement must be to wake the sensor in modes 0 to 2. A lower value catches lighter knocks and vibration, and makes the sensor report more often; a higher value catches only the harder ones.

Orientation

The accelerometer sits on the circuit board, in the same plane as the back of the sensor. It measures along three axes: two in the plane of the back, and the third straight out through the front.

• While it moves, it registers the acceleration: the burst that the spectrum and energy are worked out from.
• When it is still, the only acceleration it feels is gravity. That is what the X, Y and Z orientation values show: how the sensor is tilted relative to gravity.
• Tilt, not position: if the sensor is moved, or turned about the vertical axis, without being tilted, X, Y and Z stay exactly the same. Only a change of tilt changes them.
• Reporting: with Enable XYZ orientation change reporting on (off by default), the sensor reports X, Y and Z when they change, and again when it has been still for about a minute. While it vibrates the values can look odd, and they are reliable only in Spectrum Reporting Modes 0 and 1.

On warehouse racking

• Mount the sensor with its back flat and rigid against the upright, so that it moves with it.
• A knock from a forklift shows as a burst of acceleration: a motion report and its energy.
• If the upright is bent or knocked out of plumb, the orientation changes as well.
• If the upright is pushed sideways without tilting, the knock is registered, but the orientation stays the same.

Temperature

The temperature is measured inside the sensor every 15 minutes, with a typical accuracy of ±2 °C. It is an indication of the conditions around the sensor, not a precise air temperature.

• When it has changed by more than the Temperature Hysteresis (2 °C by default) since the last value sent, the sensor sends the new reading.
• Every Average Temp Interval (2 hours by default), it sends the average temperature, if it has changed by more than the same hysteresis.
• Above the Temperature Alarm High Level (60 °C) the alarm state becomes “high”, and below the Temperature Alarm Low Level (2 °C) it becomes “low”. The alarm is sent confirmed, and cancelled when the temperature is back between the levels.

Battery and position

Once a week the sensor estimates its remaining battery and sends it as a percentage. Once a day, while joined, it scans for Wi-Fi access points and sends the result, so that a cloud service can give its position (see How Wi-Fi positioning works).

How Wi-Fi positioning works

• 2.4 GHz only: the radio scans only the 2.4 GHz band (2412–2484 MHz). Networks that broadcast only on 5 GHz are not seen.
• Passive: the sensor listens for nearby Wi-Fi access points (802.11 b/g/n) and records their MAC addresses and signal strength (RSSI). It does not connect to any network, needs no password and sends nothing over Wi-Fi. The addresses travel in the LoRaWAN uplink.
• How many: at least 2 access points are needed for a position, and more give a better one.
• The position: a cloud service that supports Wi-Fi positioning is needed for a position, for example Yggio (Munin and LoRa Cloud can also do this). It looks the addresses up in a database of mapped access points and returns the position.
• Accuracy: depends on how many known access points are around: typically 5–20 m indoors. With only one or two, expect the area rather than the room. Adding low-cost 2.4 GHz access points improves it.
• Wi-Fi only: Square Impact has no satellite positioning.

Network

• Confirmed messages: the spectrum, the orientation and the temperature alarm are acknowledged by the network server, and the sensor sends them again if no acknowledgement arrives.
• Rejoining: if the sensor is not joined, it tries to join once every 24 hours. An NFC touch, as in step 3, starts a join attempt at once.
• Losing the network: the sensor gives the network up if it hears nothing from it for the Downlink Timeout (24 hours by default; see Device registers).
• Adaptive data rate: the sensor sets its own data rate and transmit power (sensor ADR, not the network server’s ADR), and the application damps and limits those adjustments. This suits a sensor mounted in one place, where the radio conditions change slowly.

Decoding the messages

The messages are compact binary records, and their meaning depends on the application version. Decode them with a VSM-aware decoder:

• Yggio decodes them with its built-in VSM translator, and keeps track of each sensor’s application version.
• Other platforms: use Munin, Sensative’s open-source MQTT client. It decodes the messages for any network server, keeps the device state the decoder needs and the device time up to date, and solves Wi-Fi positions.
• Your own integration: the open-source VSM translator is the decoder that Munin uses, available as a Node package. It needs two things from you: it must be able to store at least the rulesCrc32 for each sensor between messages, and it must be kept up to date, since new application versions are released without notice.

Changing the settings

There are two ways: over the air, with downlinks from your network server, or on site with the Hugin NFC app. Both usually start in the VSM Configuration Tool, which makes the downlinks for you.

1. Pick the application: by name and version, or by the rulesCrc32 from the sensor’s port 15 message (see Which application is in the sensor).
2. Choose a configuration: a released profile from the Profile Library (none are released for this application, see Released profiles), or Custom to set your own values. Each setting shows its description, unit and range.
3. Take the result: one or more downlinks for port 2, or a single payload for port 7, in hex or base64, to send from your network server. Or a QR code to scan with the Hugin NFC app, which then writes the configuration to the sensor on site.

5The Hugin NFC app

Hugin is an optional Android app for working with the sensor on site, over NFC. It needs an Android phone with NFC and GPS, and an Yggio user account. The sensor must also be registered in Yggio with your organisation as its owner: Hugin checks this with Yggio before it lets you work with the sensor. Hold the phone to the sensor as in Finding the NFC antennas. The app then shows the serial number, the application and its version, the state (for example joined), battery, link and region information, and the DevEUI. Depending on your rights in Yggio, it can read and apply configuration profiles, including one scanned as a QR code from the VSM Configuration Tool, and update the device time and position.

Installation, sign-in, flashing and troubleshooting are in the Hugin NFC app manual.

6Maintenance and removal

Battery

The battery is built in (4,000 mAh); battery life depends on the mode and how often it reports. Frequent reporting and a weak link shorten it.

Removing Square Impact

Slide dental floss behind the sensor and saw gently through the adhesive.

Moving to another network server

Delete the device from the old network server and add it to the new one. The sensor’s link check then fails, it leaves the old network and joins the new one. This usually takes one to two days. With the Hugin app you can restart it at once instead (Toggle On/Off), but that also resets any custom settings.

Storage and disposal

• Store unused sensors at +10 to +30 °C.
• The sensor contains a non-replaceable lithium manganese dioxide (LiMnO₂) battery, one of the most stable lithium chemistries. Do not open the sensor, and do not puncture it or heat it above +80 °C.
• When the battery is empty, dispose of the whole sensor as a battery, for recycling. Near the end of its life the battery normally swells a little; this is expected.

7Troubleshooting

8Technical reference

For integrators. The values below are for the application Motion-spectrum R31–R33. Other versions can differ: check the VSM application documentation or the VSM Configuration Tool for yours.

Which application is in the sensor

Right after it has joined, the sensor sends its application identity, the rulesCrc32, on port 15. The decoder uses it to pick the right translation, and you need it to make the right downlinks. For this application it is:

If you missed the message, send 00 on port 15 and the sensor sends its identity again. The Hugin NFC app also shows the application and its version on site.

Alternative applications: besides Motion-spectrum, Sensative can offer other VSM applications for the same hardware. They are available in the Hugin NFC app (Android) and can also be loaded into the sensor over LoRaWAN. Ask Sensative which applications fit your use. After a change, ask for the identity with 00 on port 15 and use the documentation for that application.

LoRaWAN and ports

Messages

Each output has an id and a scale. “Confirmed” outputs are acknowledged by the network server.

Settings

The defaults are the values the sensor starts with. The id is what a port 2 downlink uses. Values are sent in the steps shown: the Motion Threshold in steps of 0.001 is sent as a thousand times its value, the Temperature Hysteresis in steps of 0.01 as a hundred times; the others are whole numbers.

Device registers

These belong to the sensor’s firmware rather than to the application, but the application uses them and they can be changed the same way. Leave them as they are unless you have a reason.

Released profiles

No ready-made profiles are released for this application. The sensor starts with the defaults in the settings table; to change them, use Custom in the VSM Configuration Tool.

Settings on port 2

A port 2 downlink is a list of records of 5 bytes each: one byte for the setting’s id, then the value as a signed 32-bit integer, most significant byte first. The value is in the setting’s own steps: a Motion Threshold of 0.5 m/s² in steps of 0.001 is sent as 500. Negative values are written in two’s complement, so −10 becomes FF FF FF F6. The sensor applies the values and answers on port 2 with the values it now has.

Reading values

A port 2 downlink of one to four bytes is a read request: the sensor sends back the current value of each id in it.

A whole configuration on port 7

The VSM Configuration Tool can also pack a configuration into a single port 7 payload. It starts with the application’s CRC and ends with a checksum of the configuration (configCrc32). The sensor reports the result on port 7: None, Applied, Error or Dirty.

Worked example 1: A spectrum every hour

Measure every 60 minutes, whether or not the sensor has been woken, for example to follow a machine’s vibration over time. Both examples were made in the VSM Configuration Tool for rulesCrc32 4173659976. Send one of the payloads, port 2 or port 7, not both.

Worked example 2: Orientation, and only harder knocks

Switch on orientation reporting, and raise the Motion Threshold to 0.5 m/s² so that only harder knocks wake the sensor.

9Specifications

10Support

• VSM Configuration Tool, opened at this application: vsm-lora-config-app.service.sensative.net
• VSM application documentation for this version: github.com/Sensative/vsm-application-documentation
• Munin MQTT client and decoder (open source): github.com/Sensative/vsm-mqtt-client-open-source
• VSM translator (open source): github.com/Sensative/vsm-translator-open-source
• Hugin NFC app: Sensative Docs
• Support, FAQ and downloads: sensative.com/support
• Product page and product sheet: sensative.com/sensors/square-impact

Sources: Sensative Docs, Square Impact, FAQ Square & Puck and Hugin NFC application (read 24 October 2026); VSM Configuration Tool, application data for Motion-spectrum (read 26 October 2026); VSM application documentation on GitHub (4173659976-Motion-spectrum); VSM translator (open source); specifications from the sensative.com product data; Wi-Fi positioning: Semtech, Wi-Fi geolocation with LoRa Edge.