What Is a Sensor Controller?
A sensor controller is a device that applies an electric current to a sensor and outputs a control signal.
There are direct current and alternating current versions, transistor outputs and relay outputs. They receive sensor signals and output signals. Some small sensors, for example, have a built-in controller.
Since there is a wide variety of sensors themselves, it is necessary to select the controller that best suits the application. There are also panel controllers that display on a panel.
Uses of Sensor Controllers
Sensor controllers use a wide variety of sensors, such as photoelectric sensors, laser sensors, and flow sensors, each of which is connected to and controlled by a controller.
Controllers that are mutually compatible are sold as long as the standards such as current, voltage, and plug shape are matched. An increasing number of products are now available that allow multiple sensors to be controlled by a single controller. However, it should be noted that some of them may not work unless they are made by the same manufacturer as the sensors.
For example, when a sensor is used to detect the presence or absence of bottle caps in a factory, the controller receives input signals from two sensors and comprehensively determines the presence or absence, turning the output on or off.
Principle of Sensor Controllers
The controller not only supplies power to the sensors, but also has the ability to check and control the sensor values from a distance, even if the location where the sensors are installed is small.
The controller must also have a high information-processing capability to control the sensor in a short period of time and with sufficient accuracy based on the values measured by the sensor. Selection of control variables such as current, rotation speed, and position, as well as system accuracy, is important.
Sensor controllers are available with either relay or transistor contacts, and it is important to select the appropriate product for the application.
1. Relay Output
Relay output is an output method that has a mechanical contact mechanism and can be used for both DC and AC. Since the switch is turned on and off by a mechanical contact, the contact has a life span and the contact open/close response is slower than the transistor output method described below, which are disadvantages.
On the other hand, if the output unit has multiple terminals, it can handle both DC and AC, so loads with different circuit voltages, such as 200 VAC and 24 VDC, can be connected.
2. Transistor Output
Transistor output is a non-contact output type that has no mechanical contact and can handle loads from 12 VDC to 24 VDC. The disadvantage is that the current value that can be handled is 0.5A per point, which is smaller than the 2A of the relay output type. However, since there is no mechanical contact point, it has a long service life, and the contact opening/closing response is faster than the relay type.
Although only DC loads are supported, AC loads can also be driven via a relay. Basically, it compares the setting signal input from the outside with the signal sent from the sensor to control the signals so that they match and stabilize the operation.
Other Information on Sensor Controllers
1. How to Use a Sensor Controller
Sensor controllers are often used in photoelectric sensors. The greatest advantage of sensor controllers is that they can isolate the sensor portion from the output portion. Because of this feature, sensor controllers are used in the following ways:
First, it is used when the type of sensor is changed. In the past, many photoelectric sensors with 200 VAC contact switching were sold, but currently 24 VDC is the most common power supply for instrumentation. If the power supply is not available at 200 VAC when the latest model is made, the sensor controller can supply the sensor with 24 VDC voltage while sending electrical signals with 200 VAC relay contacts.
Next, it is used when increasing the number of contacts. Generally, sensors in the field have only one contact point. By using a sensor controller, multiple contact outputs can be realized while insulating the power supply between the field and the control panel. Relays can be substituted, but sensor controllers have a higher response time.
In addition, sensor controllers are often multifunctional. A timer may be installed to prevent sensor chattering, but a controller with a built-in timer can be used to save space. Some other types of sensor controllers allow the sensitivity of the sensor to be changed.
2. Sensor Controller I/O Connector
Sensor controllers may be connected to sensors with I/O connectors. Basically, the sensor has only lead wires coming out of it, which can be crimped or terminal lifted. Education and training are required to replace them, as they require the use of crimping pliers and electrical work.
By using an I/O connector for wiring to the sensor controller, the sensor can be connected with a single touch, eliminating the need for training. This not only saves time and labor in installation work, but also facilitates maintenance.