ANSI Z540.3 - Requirements for the Calibration of Measuring and Test Equipment- offers...
Process calibrators are an essential tool for technicians. They are a familiar instrument for anyone who specializes in monitoring technical equipment and keeping it accurate. They're also a must-have for those who work in a laboratory that requires precise parameters and measurements.
Just as the name implies, a process calibrator is one that’s used to calibrate a tool used for process instrumentation. The process instrumentation refers to the sensors that are built into tools used to measure physical parameters like temperature and pressure.
Process calibrators can measure and calibrate in a wide range of applications. You’ll find them needed where process instrumentation is regularly used, in industries like healthcare, chemistry, and food and beverage.
Whatever their setting, process calibrators have several uses.They’re made to work with both sensors and transmitters. Sensors respond to the change in physical conditions like temperature, humidity, and pressure, while transmitters convert the signal from the sensors to the standardized signal, which is often 4-20 mA DC electric current.
You can find process calibrators in a wide range of styles, prices, and applications. Most are easy to us, and comfortable to work with as a handheld instrument. Process calibrators can also be fixed to a surface when needed.
As we dive deeper into the world of process calibrators, we’ll look at how they work, how to use them, and why they’re so important.
Why do we need process calibrators?
There are so many fields where precision is essential, and many of them require process instrumentation to monitor different variables. These instruments are used in manufacturing, laboratory work, and research and development, accounting for variables like humidity, conductivity, pressure, level, and flow. There are so many circumstances in which process instrumentation comes into play, and thus so many chances for it to go wrong.
That’s where process calibrators step in as an essential piece of the puzzle. These instruments keep the process instrumentation on track by calibrating their readings on all the variables they may measure. Without process calibrators, there would be no way of keeping a standard in process instrumentations across the world.
How does a process calibrator work?
With a process calibrator, you can test a process device for accuracy in just a few easy steps. A process calibrator works its magic by flipping between several different roles. It can both measure process parameters — such as checking the accuracy of pressure or temperature — and source these parameters. In other words, it starts by checking a sensor’s read for accuracy, and ends by mimicking the output of that sensor to check the transmitter’s signal.
There are a lot of different process calibrators on the market, but many are designed with different modes that are easy to understand. They can match different types of signals that need measurement, and turn around to simulate those signals with the push of a button.
Process calibrators can serve to source or simulate a current loop. For instance, a transmitter is an example of a source that sends 4 to 20 mA signals. They are connected to a programmable logic controller (PLC), which reads the loop current. Usually, the loop gets 24 volt DC either from the PLC or the transmitter. If you want to calibrate this process instrumentation but the power comes from the transmitter, you’ll need to use your process calibrator in source mode.
If the power comes from the PLC, you will use the mode that allows you to simulate the loop. In this mode, the calibrator controls the external flow and keeps it between 4 and 20 mA.
A process calibrator switches between modes to test either sensors and transmitters by sourcing or simulating process parameters. They can work with the loop parameters in signals like mA, volts DC, frequency, or resistance. With so much versatility in this reliable tool, it’s no wonder technicians put these instruments to use on a regular basis.
How to use a process calibrator
With a wide range of applications, it might at first feel daunting to use a process calibrator. However, most process calibrators are made with a straight forward design that’s ready to use right out of the box. Process calibrators are usually equipped with clear digital displays and comfortable, ergonomic designs for easy hand-held usage. They can also be mounted when necessary.
The first step in using a process calibrator is to measure the process parameters by checking the accuracy of whatever process sensor you are working with. In order to do this, you’ll want to program the process calibrator to match the type of sensor you’re working with. Then, you can connect the output of the process sensor to the calibrator. You will see the measurement displayed on the digital screen. First you need to adjust the low point, and then the high.
Let’s say you want to calibrate a resistance thermometer. You can test the sensor’s accuracy by using water as a reference, getting the 0 degrees celsius reeding at freezing, and 100 degrees celsius at boiling.
Next, you’ll need to test the transmitter for accuracy. You’ll do this with the versatile process calibrator as well. In this step, the process calibrator will serve to simulate the process sensor that you just measured.
You’ll begin this step by connecting your calibrator to the transmitter’s input. The transmitter’s range is most likely registered between 4 to 20 mA, as this is the most standard current loop measurement. This means that the low end of the process sensor’s range should register at 4 mA, and the high end should measure at 20 mA. In the example of a resistance thermometer, you want your process calibrator to read 4 mA when it simulates 0 degrees celsius, and 20 mA when it simulates 100 degrees celsius.
The actual calibration step is simple. You will adjust the current value with the zero and span buttons until it matches the temperature being simulated by the calibrator. After that, both the sensor and the transmitter should be reliably accurate for further use.
Wondering what we calibrate? Check out our Visual Index.
Phil Wiseman is Chief Marketing Officer at Alliance Calibration. He earned a B.S. in Chemical Physics from Centre College. Phil is an ASQ Certified Quality Auditor and ASQ Certified Manager of Quality/Organizational Excellence.
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