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IO-Link is a standardized digital point-to-point connection between a sensor and an IO-Link master. It runs over an ordinary unshielded three-wire sensor cable with an M12 connector. Measured value, parameters and diagnostics all travel over the same line.
For load cells and force transducers this means: the measuring amplifier sits in the sensor or in the cable, and instead of a sensitive millivolt signal a finished numerical value arrives in the controller.
3 wires
unshielded standard cable, M12, M8 or M5
up to 20 m
cable length between master and sensor
up to 230.4 kBaud
three transmission rates: COM1, COM2, COM3
IEC 61131-9
international standard, vendor-independent
How an IO-Link system is built
An IO-Link system has three parts: the devices in the field, the master whose ports they are connected to, and the controller that the master talks to over the existing fieldbus. IO-Link does not replace a fieldbus; it is the last stretch to the sensor.
IO-Link device
the sensor or actuator in the field, for example a load cell with an integrated IO-Link amplifier
IO-Link master
the gateway with several ports; it translates IO-Link to PROFINET, EtherNet/IP, EtherCAT or another fieldbus
IODD
the device description as an XML file; it provides parameters, units and texts for the master and configuration software
Cable
unshielded standard sensor cable with three or five cores; connectors M12, M8 or M5
What travels over the line
IO-Link transmits more than the measured value. The standard defines four kinds of data:
Process data
the cyclic measured value, for a load cell the force or weight as a number
Value status
whether the process value is valid
Device data
parameters, identification and serial number, for example measuring range, filter or switching points; read and written as needed
Events
messages the device sends to the master on its own, for example on overload or a fault
If no master is connected, the signal pin works in SIO mode as a conventional switching output. Some devices then also offer an analog signal, the LBOA for example 4…20 mA.
IO-Link technical data
| Feature | Value |
|---|---|
| Standard | IEC 61131-9 (SDCI, single-drop digital communication interface) |
| Connection | point-to-point, one device per master port |
| Cable | unshielded, 3 or 5 cores, up to 20 m |
| Connector | M12, M8 or M5; port class A up to 4 pins, port class B 5 pins (M12 only) |
| Pin assignment | pin 1: L+ 24 V · pin 3: L− 0 V · pin 4: C/Q (communication or switching output) · pins 2 and 5: auxiliary power for class B |
| Supply | 24 V DC via the master |
| Transmission rate | COM1 4.8 kBaud · COM2 38.4 kBaud · COM3 230.4 kBaud |
| Cycle time | from 0.4 ms at COM3; the response time of the amplifier comes on top |
| Device description | IODD (XML), available in the IODD Finder of the IO-Link Community |
| Extensions | IO-Link Safety for safety functions, IO-Link Wireless for radio |
Why IO-Link for load cells and force transducers
A strain gauge bridge delivers only a few millivolts. Over long cables and next to frequency converters this signal is prone to interference, and it needs an amplifier in the control cabinet. With IO-Link, both disappear:
No millivolt signal on the line
digitized directly at the sensor; the cable only carries numbers
No separate amplifier
the electronics sit in the sensor or in the cable and save space in the cabinet
Configuration from the controller
measuring range, filter, zero and switching points are set by software
Easy device replacement
from IO-Link 1.1 the master stores the parameters and writes them back to the new device
Diagnostics
events such as overload or device faults arrive as messages in the controller
Standard wiring
standard sensor cable with M12 connector, no shielded measuring cable needed
Three ways to a load cell with IO-Link
Depending on the space available, the IO-Link amplifier sits in one of three places:
Integrated in the sensor
for designs with enough room in the housing, for example shear beams and tension rods
As an amplifier in the cable
for compact sensors and for retrofitting existing strain gauge load cells
As an OEM board
for installation in your own sensors and devices, rectangular, round or two-channel
IO-Link products from octogon
All amplifiers and boards are listed under IO-Link strain gauge amplifiers. For overload shutdown there is the EOMF with its own overload circuit to PL c / SIL 1 (TÜV Nord), parallel to the IO-Link measuring chain; more under functional safety.
More sensors with IO-Link
IO-Link is not limited to force. With the same master you can also read temperature and flow:
Flow and temperature
thermal flow sensor QEKD with colour display
All products
the complete range under IO-Link sensors and measurement electronics
Converting existing sensors to IO-Link
A load cell that delivers an mV/V signal today can usually be converted to IO-Link without changing the spring body: with an amplifier in the cable or, if there is room in the housing, with a built-in board. We also equip custom designs with IO-Link, see custom force transducers.
IO-Link for your application
Tell us the rated load, design and installation situation. We will tell you whether a standard load cell with IO-Link fits, an amplifier in the cable or a board in the housing.
Frequently asked questions about IO-Link
What do I need to operate an IO-Link load cell?
An IO-Link master, a standard sensor cable and the IODD file of the device. The master connects to the fieldbus of your controller; the IODD is available in the IODD Finder of the IO-Link Community. With the LZMC, for example, master and cable are not included.
How long can the cable be?
Up to 20 m between master and device, with an unshielded standard cable. A shielded measuring cable as for an mV/V signal is not needed because only digital values are transmitted.
Does the load cell work without a master?
Only to a limited extent. Without a master, the signal pin works in SIO mode as a switching output. The LBOA then also delivers 4…20 mA. The LZMC has no analog signal and needs a master for commissioning and operation.
Which controllers and fieldbuses work with IO-Link?
All for which an IO-Link master exists, for example PROFINET, EtherNet/IP, EtherCAT or Modbus TCP. IO-Link is vendor-independent; sensor and master do not have to come from the same manufacturer.
What happens when a sensor is replaced?
From IO-Link 1.1 the master can store the device parameters. When an identical device is fitted, it writes them back automatically and the machine keeps running without new settings.
How fast is IO-Link?
Transmission runs at up to 230.4 kBaud and the cycle time starts at 0.4 ms. With load cells the amplifier usually sets the pace: our IO-Link transmitters and the LZMC have a response time of 20 ms, plus the filter.
Can I retrofit my existing strain gauge load cell?
Yes. The EMMA amplifier takes one strain gauge full bridge and outputs the value via IO-Link. For installation in a housing there are the OEM boards EOMC (rectangular) and EOMD (round).
Is IO-Link available for safety functions?
There is the IO-Link Safety extension for this. For overload shutdown on load cells we offer the EOMF: it has its own overload circuit to PL c / SIL 1 that works in parallel with the IO-Link measuring chain. For higher levels there are redundant transducers up to SIL 3 / PL e.
Send your enquiry via the quotation form or to office@octogon.org.