17 Jun 2020

The EM1 just got smaller!

Mechan Controls launches smaller EM1 expandable safety relay

Four years ago Mechan Controls launched its innovative, modular EM1 safety relay with the aim of offering an 'intelligently simple' safety relay that was expandable and, more importantly, non-programmable. After thousands of units had been sold into a variety of applications and industries, the decision was taken to make further improvements to the existing design.

The main objective of the EM1 was to eliminate fault masking, without the need for programming, and this was achieved using the ESM extender module. In order to achieve CAT4, SIL3, PL-e, each dual-channel safety device must be connected to its own set of safety inputs. However, this method meant the old EM1 required a considerable amount of space compared with a programmable safety relay.

The second thing Mechan Controls addressed in the new design was the limitation on the number of ESM extender modules that could be added. The previous version supports a maximum of 12 modules; this was due to the power limitations, as each extender module drew power from the EM1 master control unit.


The new EM1 is now one-third of the size and features a host of new features and technological advances over its predecessor. Mechan Controls' experienced hardware and software engineers have used the latest design methods to reduce the size, double the number of extender modules that can be added and improve the diagnostic features.

Key features include:

  • Dual-channel outputs
  • Dual-channel inputs
  • No programming required (ready-to-use out-of-the-box)
  • Expandable up to 25 ESM units (a total of 26 dual-channel safety devices can be connected to one system)
  • Automatic or manual reset options
  • Cross-compatibility with older model
  • Normally-closed volt free signalling output (included on both the EM1 and ESM)


Each EM1 and ESM includes two cross-monitored safety inputs that are designed to accept any dual-channel, volt-free safety device. These can include:

  • Grab-wires
  • Emergency stops
  • Non-contact safety switches
  • Mechanical interlocks
  • Foot switches
  • Many more...

It is strongly recommended that users connect one dual-channel safety device per set of safety inputs to achieve CAT4, SIL3, PL-e.

Improved diagnostics

The new EM1 design features advanced software via the use of microcontrollers. This method of design meant Mechan Controls has been able to include more 'intelligent diagnostic checks. These include:

  • Improved safety input monitoring; this means each safety channel is now independently checked by the EM1/ESM. If a fault is detected on the safety device, it will now display which channel is faulty, enabling the user to easily diagnose the issue.
  • Nuisance tripping detection intelligently checks to see if the signal is a genuine fault. For example, if one channel on the safety device changes state (maybe caused by shock or vibration), it will check to see if this is a one-off fault or recurring. If it detects the signal once and it falls within the specified safe parameters, it will ignore the signal. If the problem occurs three consecutive times, the EM1 will go into a fault mode, turning off the output to the machine.


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