CANopen Position Sensors: Selection and Supply for Indian Machine Builders

Machine builders standardising on CAN keep arriving at the same question: can we take position measurement onto the bus rather than running it as analogue into an input card? For most of the Novotechnik range the answer is yes, and the reasons to do it are more practical than they first appear.

What moving position onto CANopen actually saves

An input card and its wiring. Each analogue position signal needs a channel, a screened cable run and a termination. On a machine with six position measurements that is most of a card plus the loom.

The analogue conversion chain. A digital sensor reports position as a number. An analogue one reports a voltage or current that then has to be scaled, and every step in that chain contributes error and drift. Removing it removes a calibration task from commissioning and a drift mechanism from service.

Diagnostics. This is the benefit that justifies the change on its own. An analogue sensor reading mid-scale is indistinguishable from a healthy sensor at mid-position. A bus device reports its own status, so the controller knows the difference between a sensor saying halfway and a sensor that has stopped talking.

Commissioning time. Parameters set over the bus rather than by trimming.

Which series carry CANopen

From the Novotechnik range we distribute in India, CANopen is available on:

Rotary sensors

• RSA-3200 — single-turn
• RFX-6900 — absolute touchless redundant heavy duty
• RSX-7900 — absolute non-contacting redundant heavy duty
• MB1-3600, MC1-2800 and MZ1-2200 — multi-turn

Linear transducers

• TH1
• TP1
• TM1 with plug-in flange and TM1 with screw flange
• TF1

Several of these also support IO-Link — MB1-3600, MC1-2800, TF1, TH1 and TP1 — which is worth knowing if your architecture uses IO-Link masters at the machine level rather than CAN throughout.

What to confirm before ordering

Fieldbus variants are configured to the protocol at manufacture. This is not a setting that can be changed on site, so the following need to be right at order stage.

1. CANopen specifically, not CAN generally. CANopen, J1939 and proprietary CAN implementations all run on the same physical layer and do not interoperate. Confirm which one your controller actually speaks.
2. The device profile. Encoder devices commonly follow CiA 406. Check your master expects that profile.
3. Node ID and baud rate setting method. Whether these are set by hardware switch, by configuration over the bus, or fixed at order.
4. Termination. Whether the sensor includes a terminating resistor or whether you supply it. A bus terminated twice, or not at all, is a classic commissioning fault.
5. Redundancy. RFX-6900 and RSX-7900 offer redundant measurement channels. If the position feeds a safety function, specify this at the start.
6. The EDS file. Ask for it with the quotation, not after delivery.

When analogue is still the right answer

Bus is not automatically better. Analogue remains sensible when you need one position signal rather than several, when the controller has a spare analogue input and no CAN master, when you are replacing a single sensor in an existing machine, or when the maintenance team is set up for analogue troubleshooting and not for bus diagnostics. Converting one sensor to CANopen on a machine that is otherwise entirely analogue adds complexity without collecting the benefit.

Where a mixed approach makes sense, several of these series are available in both analogue and bus variants, so the mechanical design can stay identical while the interface differs.

Ordering

Send us the measurement required — angle or stroke — the controller and CAN master you are using, the profile expected, the mechanical arrangement, the protection rating needed, and whether redundancy is required. Accent is the sole authorised Novotechnik distributor for India and SAARC, so configuration questions go back to the factory rather than being guessed at.