In the manufacturing world almost everything is operated by a feed back control system. Typically the feedback process loop uses a low current signal that operates on 4 to 20mA DC to operate. The purpose of the loop system is to transmit the process signals generated by a transmitter or transducer to a display or controller. Loop calibrators are used to ensure that these loops are performing the tasks they are assigned at the proper values. In the loop system the transducer or transmitter is used to regulate the flow or current in the loop and indicate a value between absolute zero (4mA) to full scale (20mA) and the controller will use this information to regulate the process it is in charge of based on a set of preprogrammed values. Loop calibrators are used to test and adjust these loop systems to make sure that they continue to operate within their specific parameters. Loop calibrators are also called a process loop calibrator or even a 4-20mA calibrator depending on the manufacturer and the individual describing the tool.
The basic function of a loop calibrator is to measure the output of a 4-20mA transmitter or transducer and it can generate its own 4-20mA signal for testing purposes like digital multimeters does. When used to test and calibrate a process loop the calibrator is used to measure the output of the transmitter or transducer so that it can be compared to specifications. If it is found to be out of specifications the item can then be calibrated and brought back into spec. On the other hand if the process seems to be working normally but the display shows it being out of specifications the Loop calibrators can be used to send a known reference signal to the display to verify whether or not it is reading correctly. If the display is found to be reading erroneously the display or its drivers can then be replaced and the system can continue to operate normally and the operator can stop worrying about the process. When you are looking at Loop calibrators there are a few things to know before you buy one.
Accuracy is very important when you use a loop calibrator to test a process loop. Make sure that the one you buy has a high level of accuracy at both short term (temperature) readings and long term (time) drift. You also need to know what type of system you are going to be working with, either T/C or RTD while some of the more expensive ones can work with both it is something you need to be aware of. Make sure that the Loop calibrators you are looking at have built in protection in case you accidentally connect them to higher voltages than they are designed for, if you hook your meter up to more than 30VDC will it be destroyed or is there a built in protection circuit? How well the case is designed is important and being able to withstand a certain amount of rough handling is necessary due to nature of the job the calibrator is to use for. When you are ready to equip your shop or maintenance facility with Loop calibrators take the time to look at the ones available at Tek-Inst. They offer there different levels of loop calibrator to take care of your needs from the basic level all the way up to a full multi function meter that can test more than just your loop process system.
