Connect Any 4-20mA Devices to LPWANs With Current Loop Sensors

The Internet of Things (IoT) is transforming industrial operations in many ways.

With low-cost, low-power sensors, manufacturers can monitor on-site processes and signals with outstanding efficiency. Rather than measure inputs manually, operators can configure devices to collect information based on specified triggers or at certain intervals.

For example, IoT sensors can send alerts when temperatures exceed or drop below predetermined thresholds. They can measure liquid levels in tanks at the same time every day or collect pressure readings every few hours.

With modern technology, it’s easier than ever to automate the flow of information between internet-enabled devices. Manufacturers can deploy and manage hundreds of sensors simultaneously and reallocate their human resources to more complex tasks.

Now, operators can even take off-the-shelf 4-20mA devices and connect them to leading low-power wide-area network (LPWAN) standards, such as LoRaWAN and Sigfox. They no longer need to purchase LPWAN-specific sensors to take advantage of automated data channels. Instead, they can use 4-20mA current loop sensors that act as bridges between wireless 4-20mA devices and the cloud.

Here, we explain the advantages of using 4-20mA current loop sensors and highlight the ways that operators are using them in real-world industrial applications.

An Overview of 4-20mA Current Loops

The 4-20mA loop standard is the status quo for process control.

In 4-20mA current loops, 4-20mA sensors send readings to transmitters, which then convert inputs into electrical signals between 4 and 20 milliamps. These electrical signals are sent to receivers for processing via current loop devices. Receivers can exist within LPWANs that are well-suited for IoT and machine-to-machine applications with low speed and bandwidth requirements.

4-20mA sensor readings are easy to interpret. Signals on the low end of the range correspond to low variable measurements. Those on the high end correspond to high variable measurements. Readings that fall below 4 milliamps or above 20 milliamps may indicate that something is not right in the industrial process being monitored.

For example, an operator might want to track tank water temperature throughout the year. He could set 32 degrees Fahrenheit to 4 milliamps and 212 degrees Fahrenheit to 20 milliamps. In this scenario, the transmitter would convert a 100-degree reading into a 9.43 milliamp signal. The current loop sensor would transmit this signal to a receiver capable of processing the information.

Previously, operators had to purchase 4-20mA devices that were built for specific LPWAN technologies. Fortunately, there are 4-20mA current loop sensors available that can integrate with third-party industrial sensors and next-gen LPWAN standards. Operators can virtually convert any low-cost 4-20mA sensor into an LPWAN sensor.

Current loop sensors are versatile, enabling industrial manufacturers to track many types of process control variables. Below are several examples of how manufacturers are using these devices today.

Current Loop Sensor Use Cases

When it comes to industrial applications, there are some process controls that are more prevalent than others. Many manufacturers track temperature, air quality, air pressure, liquid presence, and movement in their facilities.

With current loop sensors, operators can purchase 4-20mA differential pressure transmitters that can automate readings in boiler rooms, power stations, and clean rooms. They can also install sensors in industrial HVAC systems and vacuum cleaners.

By connecting these transmitters to 4-20mA current loop bridges, these devices effectively become LPWAN pressure sensors for IoT applications. The most sophisticated 4-20mA current loop devices can send pressure readings up to several miles to the cloud for processing over leading LPWAN standards.

Similarly, applications involving extreme temperatures no longer require expensive LoRaWAN or Sigfox-specific temperature sensors. Operators can purchase generic 4-20mA temperature readers and quickly establish automated environmental monitoring in their industrial plants.

They can ensure safe working environments for employees and appropriate air conditions for sensitive assets. 4-20mA thermocouple sensors can be used in conjunction with current loops to track extreme temperatures, including those involving cryogenic chambers and incinerators.

4-20mA current loop devices also work well with liquid sensors. Those who want to capture liquid depth readings in storage tanks or fuel containers can easily do so with generic 4-20mA water presence sensors and current loops. Operators can install rope sensors in data rooms and measure water temperature in pipes.

Data readings can also be automated for applications involving heavy machinery and equipment. Off-the-shelf 4-20mA vibration sensors and inclinometers become LPWAN sensors when connected to the right type of current loop bridge. 

Operators can configure devices to send alerts when equipment is vibrating too much or tilted at a unusual angles. They can automate early failure detection and detect movement-related anomalies instantly with accelerometers.

On the air quality front, there are many sensor variations for detecting different types of gases. Current loop sensors can connect 4-20mA carbon monoxide, methane, ammonia, and benzene sensors directly to LPWAN networks. Operators can also install ambient light sensors throughout their premises to automate light intensity readings.

Reducing Barriers to the IoT

Overall, the versatility of current loop sensors opens up a world of possibilities related to third-party IoT sensors. Establishing critical process controls no longer has to be a capital-intensive endeavor for manufacturers that want to take advantage of the IoT.

Manage hundreds or thousands of sensors without the setup or ongoing costs associated with high-powered, LPWAN-specific devices. Instead, build IoT networks with equally effective, yet inexpensive third-party products and current loop sensors.

Whether you need to guard against environmental concerns, protect employees, or track machinery, current loop sensors are the answer for those exploring ways to cut costs when deploying innovative IoT applications.