Weight Scales with 4-20ma Output Options

At Arlyn Scales, we are dedicated to helping you achieve solutions for all of your weighing requirements with a maximum of ease. Our knowledgeable engineers and technicians are constantly searching for new protocols that will advance the weighing industry and it is for this reason, as well as our attention to quality control and great customer service, that we are number one in the field.

Since the 1960s, 4-20mA has been available as a communications protocol for data collection and systems monitoring. 4-20mA is still widely used today with remote indicators, PLC’s, and legacy equipment. They may be outmoded, but 4-20mA offers the ease of use and affordability that many other communications protocols cannot offer, making it a widely used option for our weight scales.

Connecting with Efficiency

With our attention to the newest cutting-edge technologies, as well as how to implement those that are tried and true, all of our scales can be provided with 4-20ma analog output options to help you connect more efficiently and with systems all across the board. In today’s world it is essential that your company stay ahead of the curve, so the ability to share weight information and other data with other processing equipment is one of the most crucial means for greater productivity.

Our State of the Art Sensors

Calculation of accurate weight is a necessity in all manufacturing industries; the more sensitive the output, the more precise your calculations must be. At Arlyn Scales we use state-of-the-art sensors for our 4-20ma analog output that can be used in a range of applications. Weight sensors are crucial in ensuring high-precision weighing, and weigh modules that contain them can offer the highest levels of linearity, repeatability and speed. They are tailored to the needs of machine and equipment manufacturers for simple electrical and mechanical integration. Some of the areas where this type of protocol is especially effective are in industries that deal with medical materials, wind measurement, green energy, robotics, the military and aerospace industries, to name but a few.

Connecting From Any Location

Our scales incorporate 4-20ma analog output in order to enable sensors to interface with machines from any location. This means that there is always a reliable signal available for a direct or wireless connection. Fully isolated, the 4-20ma is able to work with current loop voltage and can be applied with any type of appropriate input channel.

Some advantages of the 4-20mA current loop are:

  • Data transmission is not affected by voltage drop over interconnecting wiring, which means it can be used over long distances without losing quality of the signal.
  • It allows the system to self-monitor since currents less than 4mA and higher than 20mA indicates a fault in the circuit.
  • 4mA is considered “live” or “elevated” zero which allows the device to be powered even with no process signal output from the field transmitter.
  • A 4-20mA current loop is often used also to power the remote device.

The Current Loop

A current loop is what is commonly used for digital communications. It is a popular communications interface that uses a current for signaling, rather than voltage. 4-20mA communication starts with a current loop circuit that provides the supply voltage and measuring current using only two wires. It can be used over relatively long distances and is able to function with optically isolated links,making it an extremely versatile and useful tool for communicating data in real time. For example, a base current signal of 4mA is an indication of a loss of signal due to a poor connection or to a 0mA current signal as a result of a broken wire. With a programmable range along with channel assignments, the protocol allows for data transfer throughout your entire network.

Accurate Analog Signaling

Unlike a digital signal, which has a separate value at each sampling point, an analog signal has constant fluctuations and a continuous signal that contains time-varying quantities. The 4-20ma has generally been used for analog signaling to ensure that the accuracy of a signal


is not affected by a possible drop in voltage within the network of interconnecting wiring. The loop provides operating power to the device, and even if electrical resistance occurs in the line, communication remains status quo. This means you never lose contact with information as it is fed into the system due to the current being maintained up to its maximum voltage capacity at all times.

Consistency All the Way Down the Line

In an analog environment, it is important to have an end-to-end direct current, or DC, to ensure that the current is consistent all the way through the line. With process automation, a point-to-point multi-drop circuit is used in order to transmit signals from the scales and sensors to a controller, which in turn sends an analog signal.

For more control over the process, a 4-20mA scaling calculator exists to calculate a current (I) corresponding to a measure physical value (Pv) and also from a physical value (Pv) corresponding to a current (I). 4-20 mA signals are used to transfer a physical value, pressure or other physical quantity. The current in the loop represents the corresponding physical value.

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Compensating for Potential Failure

All electrical systems 4-20 mA loops comply with what is known as Kirchhoff’s law. Kirchhoff’s second law states the sum of all voltages in a circuit is 0. Because of the resistance in the loop, the voltage varies with the current flowing through these resistors. Therefore when the voltage supply is insufficient, the maximum current cannot be reached.

This is another reason weight scales incorporate these kinds of outputs, assuring accuracy when it comes to communication between instruments. With this, the piece of equipment on the receiving end is able to detect any failure in the loop. In this regard it will configure with the same current loop as used by the transmitting device in order to take into account pressure, temperature, flow, and other essential processes. Our equipment is designed to compensate for any potential failure so that your processes remain consistent.

Monitoring and Controlling Information

Because we create scales to configure with the latest technology, you have the ability to monitor and control all of the information that comes through your network set-up. We have made sure that setting up this network is as easy as possible, where all you have to do is plug in your Arlyn scale and connect using our Remote Indicator software that can be used to remotely monitor data with a high degree of accuracy. Once this is done, all of your weights can be recorded, grouped, sorted, and analyzed from your workstation. Additionally, a network can be set up to help you access information from anywhere in the world via the Internet. Our scales also offer wireless Ethernet options for even greater ease of use.

The Setpoint Controller

A setpoint is the target value for process value or variable in a system. A controller seeks to maintain the measured process variable at set point in spite of unmeasured disturbances. The key components of a control system include a sensor, a controller, and a final control element.

Other elements included as options for placement in our scales include a setpoint controller, which allows for simple batching and PLC type functions, as well as the ability to set up eight target weights simultaneously. The setpoint can also be used to turn other equipment on and off as desired. This function is ideal for things like feeders, mixers, motors, valves, solenoids, and other similar devices that employ solid state for function.

The Universal Serial Bus

A USB, or universal serial bus, is another common interface available on our scales. Because of its wide variety of uses, including as an option for electrical power, the USB has replaced a wide range of interfaces like the parallel and serial port. With this port, scale data can be sent to an Excel spreadsheet. It can also be used to access any database file in your PC. The PC can additionally control your scale’s operation, ultimately sending weight data directly from the scale to any Windows application software.

Other Communications Protocols

Our scales are also designed with RS-232 or RS-485 communications protocols that assist in transmitting data from one piece of computerized equipment to another, such as printers, logic controllers, and other PCs. Several variations of these two standard communication protocols are occasionally found in use. RS-422 is a simply a variation of an RS-485 and even has similar specifications but is designed only for one driver and up to 10 receivers. With this bi-directional interface, you can easily send and receive commands in order to facilitate full remote capability. With the RS-485, you can operate from a greater distance when it comes to connecting several scales to your computer. Here the scales will share a single line in order to create a fully and efficiently functioning network. The RS-485 can be used with an USB interface to log data and to control up to ten scales from just one PC.

Arlyn Scales’ Attention to Detail

At Arlyn Scales, reliability is our middle name. We make sure that all of our equipment containing the 4-20ma analog output and our other options are fabricated with the utmost attention to detail and care.

For more information on our products, please feel free to contact us by filling out our online form.