Updated Version

Belt & Pulley Misalignment Sensor


The Touchswitch is an electro-mechanical limit switch with no moving parts, which detects tracking and misalignment problems on bucket elevators and conveyors. When a belt misaligns or a pulley moves over and contacts the sensor, the built in solid-state electronic circuitry detects the lateral force of the belt or pulley and activates a voltage free solid state relay output. This output signal is used to immediately alarm and ultimately shutdown the machine.

The face of the sensor is made from hardened and annealed stainless steel, not soft brass or aluminium, so wear life is longer when a belt contacts it. The sensor is not affected by dust or material build up and will still work when completely covered by material. An external test wheel allows for quick and simple sensor/system testing. The sensors are usually installed in pairs on opposite sides of the machine. The sensors can be connected directly to a PLC input, or for greater safety, to a central independent monitoring system, such as Watchdog Super Elite, IE-Node or the T500 Hotbus system.

4b Touchswitch sensor
Product Features: 
  • Force Activated Belt and Pulley Alignment Sensor
  • Instantaneous Misalignment Indication
  • Hardened Stainless Steel Contact Face
  • External Test Feature
  • Output LED Indication
  • Not a Rub Block
Electronics Application: 



Supply Voltage 12-24Vdc12Vdc24Vdc
Supply Current21mA60mA60mA
TypeConduit EntryConduit EntryConduit Entry
ATEX/IECExZone 20Zone 21Zone 21
CSANot ApprovedClass II Div1Class II Div1


  • Solid state relay output (TS2V34AI)
  • Volt-free relay output: 250VAC, 5A non-inductive (TS2V4CAI and TS2V3CAI)
  • Sensor state indication via LED
  • 2m long cable, 6 cores
  • Dimensions: 89mm dia x 45mm high
  • Weight: 0.77kg

Touchswitch™ Belt Alignment Sensor Hole Saw

Recommended Tool for Touchswitch™ Sensor Installation    

  •     2-1/4” Carbide Teeth for Optimum Performance and Durability    
  •     Cobalt Steel Pilot Drill with Split Point Tip Prevents Walking    
  •     Built in Flange Stop Prevents Over Drilling    
  •     Ejector Spring Makes Removal of Slug Easier
Watchdog Super Elite hazard monitor (WDC4)
Combined belt speed (slip), belt alignment, continuous bearing temperature, pulley alignment and plug condition monitor for bucket elevators and conveyors.
IE Node

The Industrial Ethernet Node (IE-NODE) is a remote monitoring interface designed to provide sensor data to PLC’s or other automation and control systems.

Both units can be expanded to 16 sensor inputs with the installation of optional expansion boards.

T500 Elite (Hotbus) hazard monitor
Monitors up to 256 sensors: temperature, alignment, speed...
B400 Elite elevator / conveyor belt alignment monitor

The B400 Elite Beltswitch belt misalignment monitor uses 4B Touchswitch sensors to monitor belt alignment in bucket elevators and conveyors. Each control unit incorporates two independent monitoring circuits for early detection of belt misalignment on one or two bucket elevators / conveyors. The 4B Touchswitch is an electro-mechanical limit switch with no moving parts. When a belt misaligns or a pulley moves over and contacts the sensor, the built in solid-state electronic circuitry detects the lateral force of the belt or pulley and activates a voltage free relay contact.

X400 Elite

The X400 Elite is a microprocessor controlled low cost alarm indicator panel for use with level indicators, hazard controls and limit switch sensors. The X400 accepts signals from different sources in up to 8 zones, and is able to cause alarm and shutdown of the machine when an alarm condition has been detected. Alarm and status LEDs on the lid of the X400 provide quick location of alarm conditions. Alarm muting can be performed at the panel or by an optional remote push button to silence external alarms.

Is the Touchswitch™ a rub block?

No, the Touchswitch is a pressure sensitive contact switch.  When the belt misaligns and contacts (touches) the sensor with enough force, an alarm is triggered.

Rub blocks are designed to detect the heat generated by friction when the belt rubs against the brass block. In dust hazardous environments, heat is what you are trying to avoid. Also, belts can misalign and rub against the brass for a short period of time, but not long enough for the sensor to detect any heat build-up. In either scenario, rub blocks can be dangerous and ineffective in detecting belt misalignments.

Hazard Monitoring Design Service

Hazard Monitoring Design Service

Preventative maintenance can help reduce the risk of equipment failure and consequent downtimes. When it comes to monitoring your bucket elevators and belt conveyors, 4B can recommend you the ideal combination of sensors and monitoring systems to suit your requirements and budget.

4B provides an extensive range of their own ATEX / IECEx / CSA approved hazard monitoring systems, misalignment switches and bearing temperature monitors and level controls. We can offer you anything from a replacement sensor to a fully integrated hazard monitoring system which can be operated either as a stand-alone system or connected to your PLC.

And if you do not want to install hazard monitoring sensors on every piece of equipment in your plant straightaway, we can offer you a scalable solution starting with carefully chosen equipment and systems that can be expanded at a later date to encompass other machines in the plant.

We can also offer you an installation service, and we do provide a competent after-sales technical service to help you overcome any technical problems with your monitoring equipment.

To get a recommendation from our engineers, please fill in the electronics questionnaire below. Please fill this form in as accurately as possible to allow us to deal with your enquiry more effectively.

Contact Details

Elevator Information

Conveyor Information

Silo/ Bin Information

If you would like to send us a technical drawing or document with your enquiry, please send to