Any closed-loop control system requires a sensor to work correctly. A sensor is mainly a device that receives a stimulus and response through signals. Unless there is perfection in micro-scale wireless technology, sensors for control and monitoring systems need cables for power and communication. It means that the functionality of sensors highly depends on the cables. However, you cannot use the same type of cables in all sensors. There are different types of sensor cables based on size and length. Please read this blog post to learn more about sensor cables and their applications.
What is a Sensor Cable?
Sensor cables ensure optimum performance in transmitting data and signals from a transducer, sensor, or transmitter to control units. Sensor cables are a critical part of sensor technology, and thus, they must meet quality standards, harsh environments, and performance requirements of the different industrial applications. The design and construction of these cables depend on the specific application.
Image: water supply pipe with pressure control sensor
Sensor Cable Applications
In this era of modern technology, sensors are becoming a part of everyday life. Sensor technology is now an integral part of many applications in the defense, automobile, manufacturing, and medical sectors.
- Medical industry: Medical professionals use biosensors in medical devices to convert a biological signal into an electrical signal. It helps in detecting and diagnosing any disease in a patient. In addition to this, biosensors are now very common in the fitness world as they can track heart rate and monitor the user’s activity level.
- Défense industry: With the increasing use of sensors in the defense industry, there is a rise in Unmanned Aerial Vehicles (UAVs). UAVs use sensors in different ways, from temperature to optics to targeting and tracking different objects.
- Automobile market: The automobile industry has been actively using sensors in vehicles. These sensors help in breaking, parking, or assessing the proximity of the vehicles’ objects. Apart from this, with the advancement of sensor technology, soon, there can be self-driving cars on the roads.
- Industries and manufacturing: Industrial sectors which depend on control, automation, and electronic measurement, use sensor cables to perform manufacturing tasks. Sensors can transmit fluid levels, humidity, temperature, and pressure during manufacturing.
Image: sensors on patient’s hands. Diagnostics through electronic devices
How to Promote Your Signal With Sensor Cables?
All these industries above use sensors with specially designed sensor cables. These cables measure the environmental factors and transmit the data accordingly. Then, how do they ensure their performance?
Protect the signal from EMI
When you observe the sensor cables, you will see that some sensors have twisted pair cables while some others have regular cables. Do you know why?
Conductors in cables create random currents due to electromagnetic fields. This random current can cause interference in the current generated by control and automation sensor systems because of the parallel paths. So, it would help if you tried to prevent such paths as much as possible through the following ways:
Firstly, you can twist the conductors and form twisted pair cables. A twisted conductor cannot be parallel to anything, and thus the EMI effect mitigates.
Secondly, you can put a thin mesh of conducting material as cable shielding around the twisted conductors. As a result, you get shielded twisted pair cables. The twisted-pair cable prevents any parallel path while the shield looks for any possible path and intercepts EMI before reaching the protected conductor.
What signals do you need to protect from EMI?
Low-current analog signals and high-frequency digital communications need protection from EMI.
Firstly, low current analog signal cables are more prone to interruption from environmental EMI as small currents create small fields, which cause disruption easily. Twisted pair or shielded twisted pair cables help in protecting such signals.
Secondly, high-frequency digital communications like Ethernet also depend on twisted pair cabling. Various communication and control standards (Hart, Modbus, Fieldbus) specify that twisted pair cabling is suitable for the network. All types of Cat3, Cat5, Cat6, and Cat 6a telecommunications wires are twisted pairs.
Consider the cable length.
You have to consider the voltage drop only in power distribution cabling. When a power distribution cable is too long forgiven amperes and size, you need to increase the cable diameter, and it helps reduce resistance and thus the voltage drop. On the other hand, in a low-power signal and control situation, you have to change the length of the cable to adjust the voltage drop.
You can understand this with an example. Suppose there is a sensor at 300 feet of the control equipment. The circuit has 22 AWG cables and an approx 10mA current. Here the voltage drop shall be 0.0495 V. This is not too much for power delivery. However, when it comes to the millivolt signal, 49.5mV is too much voltage drop. There is no point in using a large cable in this situation. Instead, you must reduce the distance between the control equipment and the mV/V sensor to 30 feet.
However, this does not mean that you cannot power a 4-20mA sensor around 300 feet from the control equipment. With a 20mA current, you get a voltage drop of 0.099V. Most of the 4-20mA sensors need a 10VDC minimum. One-tenth of the voltage loss is not a problem as you deal in volts for supply and not millivolts.
Choose the suitable Sensor Connectors.
Apart from the sensor and switch cables, you also need sensor connectors technology to allow the automation process and systems to work seamlessly. These connectors join cables and components with the switches, equipment, and sensors to form integrated industrial automation systems. As a result, you get an efficient system that can increase productivity, work at max efficiency, and minimize downtime. Sensors use different types of electrical connectors. Read further to know the different types and see which one fits your needs.
VP stands for VarioPin, and these sensors are common in the Hamilton sensors product line. The VP designation indicates the number of exposed poles on the head of the connector. VP connectors have an IP68 protection rating and are autoclavable.
You will find these connectors on pH/ORP sensors lacking temperature compensation. The two-pole design of these connectors has a center core and metallic threaded connection on the outer side.
S7 & S8:
Traditional pH sensors without temperature sensation use S7 and S8 connectors, and both of them have a similar basic design. However, S8 connectors have PG13.5 mounting threads, which are not present in S7. You must avoid moisture penetration in connectors as it can lead to short circuits.
You will find M12 connectors in Hamilton ViSiFerm mA and ViSiTrace milliampere dissolved oxygen sensors and Hamilton’s Wi 2G Wireless adapter. These adapters have four or eight poles hiding in its socket. The poles of the connectors are recessed, and thus you must take care to avoid moisture penetration.
You may also know it as a D4 connector, and it has a twist-lock design that forms a reliable connection between cables and sensors. You will find these sensors only in OxyFerm FDZ Dissolved Oxygen Sensors.
These are inductive electrical sensor connectors that you can find in digital pH sensors. They also use a twist-lock design for a firm cable connection, and there are no exposed metallic connections on these connectors.
Image: automotive sensor connectors in a car
Do you need custom sensor cables? Gloom develops custom cable assembly for industrial environments. They are essential for seamless automation systems in a wide range of industrial applications.