There is another group or class of meters, called process instruments. Process meters accept similar signals, but because of where and how they're used they are commonly not listed or published in some of the mfg catalogs or lists. Many engineering applications have evolved over the years and some applications call for different devices to be used in order to measure or monitor these processes.
Say I'm at one end of my facility and wanted to monitor this process at another end, convential ways of doing this will not work. Take, for example, measuring the AC Current of a motor with a CT rated meter. The meter can only be mounted within 3-5 feet of the CT or motor. So the AC Current can be converted to a signal that will travel this distance. One common device is called a transducer.
This transducer, along with the CT, will transform this ACA signal to a DCV signal. This signal will travel the distance far better than the ACA so this allows for me to monitor the AC Current of the motor at my designated site. So here my process application has an AC Current signal converted to a DCV signal...my meter accepts a DCV signal and is scaled as AC Amperes. These are process applications and have many combinations and uses.
Common process inputs are 1-5 DCV, 0-10 DCV, 4-20 mADC and 10-50 mADC. The scales vary from application to application. Again this is where the mod centers come into play...being able to deliver a custom or special items at a very reasonable time frame.
