We've had lots and lots of application questions since Dataforth introduced its new family of loop isolators last year! As you know, the 0-20mA and 4-20mA loops have been used for a very, very long time. Yet, it seems we don't work with them often enough to get details committed to memory. Or we have had problems with current loops in the past and we just wish to forget the experiences! Here's some solid information to keep at hand for your next current loop project.

4-20mA Loop Isolator Application Note AN104 (144kb pdf)

Dataforth's loop isolators simplify your applications. If you need to add a local digital panel meter or a data logger or even a new data acquisition system into an existing loop, Dataforth has an inexpensive passive isolator to do the job. Our devices (DSCL products) take a little power from the loop (< 2 volts drop added to you loop device) to power themselves and to provide true galvanic isolation from the existing system... no ground loops or other electrical interaction between old and new systems! DSCL20, 21 and 22 models are passive two-wire isolators that are ideal for these types of applications.

For applications that require supply power be fed through the isolator, Dataforth provides the DSCL23 model that sends isolated DC voltage to power your 4-20mA device! Here's a summary of Dataforth's loop isolators:

Low-cost, Loop-powered (passive) models:


Full-function, uses supply voltage (active) models:


Go to our DSCL Series product information for more information and specifications.

A good article: 4-20mA Transmitters Alive and Kicking (82KB pdf)

Please feel free to contact our applications engineers at techinfo@dataforth.com should you need any product selection assistance.