Different applications may have different sensors. Some of the sensors are optional. The following illustrations show the locations of sensors for C280 Engines. For both the in-line engines and the vee engines, most of the sensors have the same location. For sensors that are at different locations, the differences are shown.
(1) Turbine speed sensor
(2) Magnetic pickups
Turbine speed sensor (1) - The rpm of the turbine wheel is detected by a speed sensor. The sensor is inside of the turbocharger housing.
Magnetic pickups (2) - The rpm of the flywheel ring gear is detected by magnetic pickups. The magnetic pickup is wired to the SDU which will cause a shutdown for an overspeed event.
(3) Oil temperature sensor
(4) Unfiltered oil pressure sensor
(5) Filtered oil pressure sensor
(6) Jacket water pressure sensor
(7) Oil pressure sensor
Oil temperature sensor (3) - A sensor in the oil temperature regulator housing helps to monitor the oil temperature. Excessive oil temperature can cause an alarm or a shutdown.
Unfiltered oil pressure sensor (4) - This sensor is located before the oil filters. The pressure of the unfiltered oil is compared to the pressure of the filtered oil. Oil filter differential pressure is calculated from the difference between the pressure before the filters and the pressure after the filters. High differential pressure can cause an alarm or a shutdown.
Filtered oil pressure sensor (5) - This sensor is located after the oil filters. The pressure of the filtered oil is compared to the pressure of the unfiltered oil. Oil filter differential pressure is calculated from the difference between the pressure before the filters and the pressure after the filters. High differential pressure can cause an alarm or a shutdown.
Jacket water pressure sensor (6) - Jacket water pressure is detected by a pressure sensor that is located on the elbow at the outlet of the jacket water pump. Low jacket water pressure will activate an alarm.
Oil pressure sensor (7) - The engine oil pressure is monitored by a pressure sensor. Low oil pressure can cause an alarm or a shutdown.
A sensor that monitors the auxiliary water pressure is located near the outlet of the auxiliary water pump. Low auxiliary water pressure will activate an alarm.
Oil mist detector
The concentration of oil mist in the crankcase is monitored with an oil mist detector. A high concentration of oil mist can activate an alarm or a shutdown.
Top view of a liquid detector in the water temperature regulator housing
A liquid detector may be installed in the water temperature regulator housing or in a remote water line. The detector helps to monitor the level of coolant in the cooling system.
Coolant level switch on an expansion tank
A coolant level switch may be installed on an expansion tank.
A low level of coolant can cause an alarm or a shutdown. To correct the condition, add coolant to the cooling system. Investigate the cause of the coolant loss.
Sensor for air restriction
Air restriction is measured between the air cleaner and the turbocharger. The pressure sensor detects the air filter differential pressure. A high differential pressure will cause an alarm. This alarm is typically caused by a dirty air filter.
Typically, engine protective systems include these components: control panel, gauge panel, junction box, contactor and transducer panel, wiring harness, relays, thermocouples and resistive temperature devices.
Control panel - This panel contains the start/stop controls. This panel often contains the relay control or the programmable logic control that provides protection for the engine. This panel is not mounted on the engine.
Gauge panel - Primarily, these three types of gauge panels are available: mechanical, electrical and computer display. Some gauge panels are a combination of all three types. The most common type is mechanical. Tubing from the engine sends the input to the mechanical pressure gauges. Traditional capillary tubes are used for the mechanical temperature gauges. Electrical gauges use a sending unit with variable resistance or a 4 to 20 mA signal. The computer display is used for systems with programmable logic controllers. The computer display uses thermocouples, resistance temperature detectors, and 4 to 20 mA transducers.
Junction box - The junction box provides a common location for all of the wiring connections. The junction box is mounted on the engine or on an accessory module.
Contactor and Transducer Panel - This panel contains some sensors that primarily detect the different engine pressures such as oil pressure, boost pressure, and other sensors. The sensors are connected to contactors or transducers. This panel is sometimes mounted on the engine.
Contactor - A contactor is a switch that is controlled by temperature or pressure. The temperature or pressure that triggers the switch is set to a critical setpoint. If the setpoint is reached, an alarm or a shutdown will be activated.
Transducer - A transducer converts a mechanical stimulus into an electrical signal. An external power source is required.
Relay - A relay is an electromechanical device which uses a relatively small current to control an electromagnet. The electromagnet activates electrical contacts. The contacts open and the contacts close in order to switch larger electrical currents.
Thermocouple - This device is used for monitoring temperature. A thermocouple has two different metals that are connected. A small voltage is generated when the two metals are heated. The voltage is interpreted by an electronic device in order to determine the temperature.
Resistive temperature detector (RTD) - This device is used for monitoring temperature. Temperature effects the electrical resistance of wiring. When the wire is heated, the resistance of the RTD increases. When the wire is cooled, the resistance of the RTD decreases. A device measures the resistance in order to help determine the temperature.
Wiring harness - The wiring harness connects the engine sensors to the junction box.
Setpoint - A setpoint is a critical limit of an operating parameter. A setpoint can be a temperature, a pressure, a level, a speed, and others. An alarm or a shutdown is activated if an operating parameter reaches a setpoint.