If you're planning an emergency replacement on an automated line, the first decision should not be brand. It should be feedback type and network protocol. Choose a SICK absolute encoder PROFINET unit only when the machine needs absolute position after every power cycle; if the system can safely re-home, an incremental option such as the SICK encoder DBS60 often gets the machine running with less configuration risk. I've written this recommendation dozens of times for clients in a hurry, and every time I've skipped it, the repair took longer, cost more, and ended with a second expedited delivery.
I work on the service side of industrial automation. My job is to keep plants running when a sensor or encoder stops behaving, and to make sure the replacement part fits both the machine and the control system before the line is scheduled to restart. Over the past 13 years—maybe 14, I'd have to check my work logs—I've coordinated close to 200 emergency replacement jobs, including gearbox failures and one afternoon when a forklift created a straight line through a row of photoelectric sensor brackets.
Why feedback type matters more than the encoder brand
The most expensive mistake I see is not a cheap encoder failing after a month. It's the correct part with the wrong outputs or protocol. In March 2024, a plant called 36 hours before a scheduled restart because a gearbox failure had damaged the encoder on a packaging line. The PLC print showed the existing part number, so the person in procurement ordered one more example of the SICK encoder DBS60 incremental model from the old bill of materials. That looked logical, but there was a catch: the motor control upgrade six months earlier had changed the PLC logic to expect absolute position feedback through PROFINET. The DBS60 is a solid incremental encoder for speed and direction, but it cannot tell the controller where the machine is sitting after a power loss. We stopped the repair, found a SICK absolute encoder PROFINET unit with the correct flange and interface, and updated the device configuration. The second part solved the problem. The lost time was not the encoder's fault; it was the assumption that a working part number still meant the right solution.
There is something satisfying about watching a replacement encoder come online under PROFINET with the correct device name and IP address. It only happens when I check the network variant, shaft sizes, and software files before placing the rush order.
A quick encoder decision checklist
- Can the machine re-home on startup? If yes, the SICK encoder DBS60 incremental family is often the simpler and more economical choice.
- Does the controller need absolute position immediately after power-on? If yes, order a SICK absolute encoder PROFINET unit and verify the exact product variant in the current SICK documentation.
- Will the encoder cable run near a variable-frequency drive? If yes, check shield termination and use a true RMS meter with low-pass filtering before you blame the encoder.
179 true RMS digital multimeter vs 87V true RMS multimeter
Once the replacement encoder is on its way, the next troubleshooting trap is measuring the wrong signal. Inverter drives create noisy waveforms, and an average-sensing voltmeter can show ghost voltages that make a healthy sensor line look dead. The 179 true RMS digital multimeter is a dependable everyday meter. I keep one for panel checks: supply voltage, mA on analog inputs, continuity on safety circuits. It handles nonsinusoidal waveforms better than an averaging meter, which is exactly what you need in a modern cabinet.
When the symptom is intermittent and there is a VFD nearby, I reach for the 87V true RMS multimeter because it includes a low-pass filter for VFD carrier noise. According to Fluke's published specifications, the low-pass filter is on the 87V for work around variable-frequency drives. That filter is the practical difference: it blocks the high-frequency switching content, so I can see the fundamental signal that the sensor or encoder is actually producing. I've caught intermittent position faults that were caused by noise on the line, not by a failed encoder, using that filter. Verify current Fluke specifications before buying, as low-pass filter availability is one reason many service engineers step up to the 87V.
Durability of IFM photoelectric sensors vs others
I get asked about the durability of IFM photoelectric sensors vs others because the suppliers in this space all have strong reputations. I don't have hard data on globally published failure rates, so I'll be honest about the limits of my observation. In high-vibration and washdown areas, IFM has performed very well in the jobs I've seen: the metal barrel housings, sealed connectors, and practical mounting kits prevent the two failure causes I encounter most often—mechanical impact and water getting into a poorly terminated cable. SICK photoelectric sensors have also been reliable, and I've pulled them out of service after five or six years only because a machine revision changed the mounting geometry.
What matters more than the logo is the interface. A sensor with a metal housing, sealed connector, and strain relief will outlast a plastic-bodied sensor with an exposed cable, regardless of brand. So my practical answer to the durability question is this: choose IFM when its housing style and connector fit the environment; choose another reputable brand when its mounting geometry makes the installation cleaner. Durability is a specification, not a slogan.
Where this field advice has limits
I don't want this to read as if every plant must install absolute encoders and premium multimeters. If a machine performs a homing cycle at every startup, the SICK encoder DBS60 is probably the smarter choice, because it reduces inventory complexity and purchase cost. If you never work near VFDs, the 179 true RMS digital multimeter may be all you need. This guidance is for people trying to prevent the second outage, not for anyone designing a simple fixed-speed machine with no network connection.
One more caveat: a SICK absolute encoder PROFINET unit is only useful when the control network really is PROFINET. I've seen teams select the most popular encoder from a supplier without checking the PLC network card, and then discover that the machine uses EtherNet/IP or Modbus. Check the network interface first, just as carefully as you check the shaft and flange.
And because pricing becomes part of the repair when time is short, ask what the vendor's quote does not include. I've learned to ask that question before asking for the price. A supplier who lists rush fees, configuration charges, and freight up front is more expensive-looking at first, but usually cheaper by the time the invoice arrives. Transparency is worth paying for when a line is down.
