Speed monitoring with speed monitoring relay

Monitor the maximum number of revolutions

A speed monitoring relay enables monitoring of the maximum number of revolutions in carousels or centrifuges. A hazardous situation could occur if the revolutions in a machine are too high. To protect machines and people from these hazardous situations and in order to comply with the regulations, a speed monitoring relay is used. When a machine is being calibrated, the machine must not run too fast. A stationary control relay is used to check whether the machine is actually stationary. The revolutions can be monitored by sensors such as encoders or inductive sensors. There are also speed control relays that can be connected directly to a motor, without the interference of sensors.

The ReeR Mosaic safety PLC - safety controller series has a number of modules for speed monitoring. MV0, MV1 and MV2. This way, speed monitoring can be a part of your entire security system. An MV0 can be used only with inductive sensors (proximity switches). The MV1 can be used with a single safety encoder or with a double non-safety encoder. The MV2 can be used with one or two encoders plus one or two proximity switches. Read more about machine safety products by ReeR Safety.


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Speed monitoring with speed monitoring relay - ReeR Safety
Safety level PLe - ReeR Safety

Safety category speed monitoring module

There is a number of product choices in terms of speed monitoring. In order to reach a certain safety level, a particular combination of products is required. These products can be safety encoders, inductive sensors, an encoder without safety level and a combination of these products. In the next paragraphs, various possibilities will be explained. Read more about speed monitoring in the application example.

Do you want to proceed directly to the example? Use the links below:

  1. Using the safety encoder (PLe)
  2. Using the non-safety encoder and inductive sensor (PLe)
  3. Using two inductive sensors (PLe)
  4. Using two non-safety encoders (PLe)
  5. Using a single non-safety encoder (PLb)
  6. Using a single inductive sensor (PLb)

Speed monitoring with safety encoder

Incremental SIL2 Sin/Cos encoder

The safety encoder Safecoder by ReeR Safety is in combination with the ReeR Mosaic series a SIL 3 certified safety monitor for speed monitoring. The encoder is available in a shaft or hollow shaft type and a power supply of 24VDC and 5VDC and has a new resolution of 2048 pulses. The shaft type is 12 mm in diameter, the hollow shaft type is 10 mm in diameter. The safety encoder is by default equipped with an IP65, and optionally IP67, protection level. The machine is designed to endure potential vibrations once operational. The safety encoder is able to endure vibrations and is insensitive to strong magnetic fields. The safety encoder is connected to an actuating rod and transmits the number of revolutions to the safety relay MV1, which is part of the ReeR Mosaic series. The safety encoder falls under safety category SIL 3, PLe, Cat. 4 Type 4.

Complies with the standards:

  • 2006/42/EC “Machine guideline"
  • 2004/108/EC “Electromagnetic Compatibility (EMC)”
  • EN ISO 13849-1  “Machine Safety - Operating System Components concerning safety - Part 1: General design principles"
  • EN ISO 13849-2 “Machine Safety - Operating System Components with safety function - Part 2: Validation”
  • IEC 61508 “Functional safety of electrical/electronic/programmable electronic safety-related systems - Part 3: Software requirements".
  • EN ISO 61800-5-2 “Adjustable electric actuator systems - Part 5-2: Safety norms - Functional".
  • UL (C+US) for the US and Canada
  • BGIA - Institute for Occupational Safety and Health - Germany
Speed monitoring with safety encoder - ReeR Safety
Speed monitoring with inductive sensor and encoder - ReeR Safety

Speed monitoring with inductive sensor and encoder

A safety system with safety category SIL 3 - PLe is achieved by using a non-safety encoder and an inductive sensor. The solution is redundant, because two sensors are utilised. The Mosaic MV1 monitors whether the two different sensors are recording the same speed. The detection ability of the separate sensors is verified. A detection test is run in two different positions. If one of the two observations deviates or is incorrect, an alarm signal is transmitted to the ReeR Mosaic MV1 speed monitor module.



Speed monitoring with two inductive sensors

Speed monitoring with two non-safety inductive sensors that form a dual-channel system. The individual sensor signals are monitored by the ReeR Mosaic MV0. It measures whether the sensors record the same speed. A deviant signal detected by one of the channels is also immediately detected by the safety PLC. The safety PLC transmits a safety signal.

Speed monitoring with two inductive sensors - ReeR Safety
Speed monitoring with two encoders - ReeR Safety

Speed monitoring with two encoders

The system uses a double non-safety sensor forming a dual-channel system. The safety PLC verifies that the two sensors record the same speed. Failure in one of the two channels (electrical or mechanical) causes a difference in recorded values. This difference is detected by the controller that generates an alarm signal. 

Speed monitoring with one non-safety encoder

The system uses a non-safety sensor that forms a single-channel system. The controller cannot make comparisons or verifications because it is a single-channel solution. The channel failure (electrical or mechanical) cannot be detected. The failure potentially goes undetected. Therefore it is harder to comply with the EN 61800-5-2 regulations. Therefore, speed monitoring with a single non-safety encoder has the maximum safety level of PLb.

Speed monitoring with a single inductive sensor

The system uses a single inductive sensor, forming a single-channel system. The safety PLC can not make comparisons and verifications. Sensor failure therefore goes undetected. It is harder to comply with the EN 61800-5-2 regulations. Speed monitoring with a single inductive sensor therefore has the maximum safety level PLb.