How to Choose a Fluke Multimeter or Process Calibrator for 4–20 mA Work

Automation and Control Industrial Automation and Control
1

What do the Fluke 87V and the HP 12C financial calculator have in common?

They both have an LCD and can calculate RMS with the right keystrokes. But look deeper. Both instruments have crossed into an iconic realm where the customers appreciate the stable feature set across multiple decades. The form, feel, and operation of the instruments becomes the baseline from which all line card products are measured. No longer are we singularly concerned about specsmanship. Instead, product selection is focused on getting down to work using a familiar tool that feels like a good pair of work gloves.

This article provides a working definition of the term “general-purpose” as applied to handheld multimeters. It is centered on the Fluke 87V which serves as a common reference point for the Industrial Automation (IA) technician. We then explore a subset of meters designed for 4-20 mA measurement and calibration.

Key Takeaways

  • A general-purpose instrument such as the 87V survives because its functions are optimized to the workflow of the technicians on the factory floor.

  • Boundary conditions for meter selection are explored using a meter-to-meter comparisons viewed through the lens of a working technician.

  • The Fluke 87V industrial multimeter serves as the reference point to which all Fluke meters are compared.

  • There is a boundary where we no longer ask what single handheld meter is required. Instead, we ask, “What is your second Fluke meter?”

Figure 1: The Fluke 87V and HP 12C are timeless classics in which function and muscle memory are favored over redesign.
Figure 1: The Fluke 87V and HP 12C are timeless classics in which function and muscle memory are favored over redesign.1264×948 345 KB

Figure 1: The Fluke 87V and HP 12C are timeless classics in which function and muscle memory are favored over redesign.

Disclaimer: HP and HP 12C are trademarks of HP Inc. No endorsement is implied.

This article is part of the DigiKey Field Guide for Industrial Automation

Location: Select It
Difficulty: :wrench: Technician — difficulty levels explained
Author: Aaron Dahlen | MSEE | Senior Applications Engineer, DigiKey
Last update: 22 Jul 2026

What is your second Fluke meter?

Given the iconic 87V as the anchor, what is your second Fluke meter? The answer depends on the nature of your work. For example, the T6-1000 with an open-fork current tester may be preferable to the 87V for troubleshooting three-phase motors. However, the T6-1000 is a step in the wrong direction for the automation technician who needs to troubleshoot or calibrate a 4-20 mA analog loop. Both power and control are in the panel, but the work is different.

From General-Purpose to Process Specialist

Figure 2 presents a small sample of handheld Fluke meters with the 87V as the central reference to which all meters are compared. As a rule, the further we move to the right, the more specialized the meters become.

The featured instruments represent a small slice of Fluke’s product offerings. They were deliberately chosen to demonstrate the boundaries between cost, general capability, and specialization when working with 4-20 mA current loops.

Figure 2: Handheld meters organized with the 87V as the starting point leading to increased specialization.
Figure 2: Handheld meters organized with the 87V as the starting point leading to increased specialization.1920×1148 243 KB

Figure 2: Handheld meters organized with the 87V as the starting point leading to increased specialization.

Safety in the Control Panel

Industrial control panels contain a mix of voltages ranging from three-phase 480 VAC power circuits down to low-level mA analog loops. For general-purpose panel work, we draw a conservative safety line at CAT IV 600 V. This specification encompasses the 87V, 177, T6-1000 Pro, and 789. Refer to Fluke’s Guide to Digital Multimeter Safety for more information.

Technically, we could drop down to CAT III 600 V for measurements in 480 VAC electrical distribution or feeder panels. However, once we are comfortable with a meter, it’s human nature to use it everywhere.

The delineation between the CAT III requirement for fixed shop-floor equipment and the CAT IV service entrance hazard is not always obvious. Both environments contain 480 VAC conductors. We will be tempted to use the lesser meter for both locations. Also, the distinction between CAT III and CAT IV is blurred as the control panel size increases to include high-horsepower motor drives. The twin hazards of arc flash and arc blast are present in the cabinet. It’s a matter of scale.

Consequently, as a practical safety bridge, bias meter selection toward the CAT IV-rated meters. This reduces the chance that the technician’s favorite meter will be used in a location that exceeds its CAT rating.

Safety Tip: Be sure to inspect the meter and accessories. Both the meter and the probes are part of a system that defines the combined CAT rating. If the ratings are different, the rating defaults to the lowest CAT specification. For example, a CAT IV meter connected to CAT III probes carries a CAT III rating.

Note that the probe rating is a selection criterion in DigiKey’s catalog. As an example, consider the Fluke TL175 silicone test leads and associated alligator clips.

When Is a Meter No Longer General-Purpose?

General-purpose Fluke meters such as the 87V, 177, and 789 have a large central function dial. If you know how to use one meter, muscle memory allows you to quickly transition to another. This common architecture is the very definition of a general-purpose Fluke meter. The definition is revealed in the work the meter was designed to perform. Common functions such as resistance, DC voltage, AC voltage, frequency, and continuity are all selected from the same dial.

The distinction becomes clear when we consider the meter’s current measurement circuitry. In Electronics 101 we learned that voltage is “measured across” and current is “measured through” the multimeter which is placed in series with the circuit. The T6-1000 and 773 are exceptions as they can measure current without breaking (opening) the current loop.

Returning to our working definition of general-purpose meters, Fluke has long defined a 10 A limit. Given the CAT IV stipulation along with the 10 A fuse, we can clearly classify the 87V and 177 as general-purpose meters. The 789 is almost a clone of the 87V, but the current measurement section has been recast with 4-20 mA circuitry. The T6 is close, but the current is now measured via the ammeter fork. Finally, the 725 and 773 are highly specialized instruments with a 30 V and 24 mA maximum for all terminals.

Tech Tip: Never substitute a meter fuse as fully explained in my DigiKey TechForum article. Refer to Fluke’s fuse selection tool to identify the fuse for your meter.

Which Fluke Meter Should I Purchase for 4-20 mA Process Work?

Now that we have a common frame of reference we can explore meter selection through the lens of work. We will do so by exploring meters in pairs. The selection lessons will help you find the best meter for your application.

Comparing the Fluke 177 to the 87V

By our working definition, both meters are general-purpose with a CAT IV 600 V rating. Cost is the overriding factor. Keep in mind that the meters are not identical. Unfortunately, I cannot offer a hard recommendation. You will need to carefully compare the fine specifications to determine which meter is the best fit for your application. This includes the meter’s resolution, the ability to measure temperature, and advanced features such as the 87V’s low-pass filter for AC voltage measurements.

Comparing the Fluke 87V to the 789

This is my favorite comparison as the meters are very similar. Side by side, they have the same look and feel. Both would be at home in an IA toolkit.

The primary difference is the 789’s inclusion of a 4-20 mA receiver and transmitter. This allows the meter to interface with a PLC’s 4-20 mA analog section in two ways:

  • The 789 can simulate the 4-20 mA sensor. The meter can be set to a specific current or it can sweep through the current. As an example, consider a pressure sensor installed 50 feet away from a PLC. The meter could be connected directly in place of the pressure sensor to test the operation of the PLC analog input card. It could also be placed at the end of the cable in place of the sensor. This would differentiate between a defective sensor from a defective cable from a failed PLC analog input card.

  • The 789 can simulate the PLC. In fact, it can even provide the source of power for the loop. This allows field devices to be operated independently from the PLC. For example, the 789 can be connected directly to a current-to-pressure transducer. As before the placement relative to the cable is important to distinguish between failures of the PLC output card, cable, and transducer.

Note that a general-purpose Fluke 177 and 87V can measure the 4-20 mA current. However, the resolution is poor when compared to dedicated instruments. Also, the general-purpose meters do not contain a loop transmitter.

Comparing the Fluke 789 to the 725 and 773

The 725 and 773 are highly specialized instruments designed to interface with the 4-20 mA process loop. They do not have general-purpose capabilities. Consequently, this becomes a two-meter solution.

What is your second Fluke meter?

For most shops, one general-purpose (87V or 177) or power-centric meter (T6-1000 Pro) is issued to the technician. The 725 or 773 will remain in the shop and be used only when the specialized function is required.

Tech Tip: In my younger days, I served as supervisor of an electronics shop tasked with maintaining the ship’s radio, sonar, gyro, and other bridge equipment. I learned some important lessons about the nature of work and tools.

First, make sure you have all the tools you need for the job. The ship was only 399 feet long, but it took considerable time and talent to retrieve the correct tools without being distracted. Second, I learned that the community tool chest was a terrible idea for common tools. You would be surprised how hard it is to locate the 1/2-inch socket or a multimeter.

What I’m trying to say is you will likely be time and money ahead if you issue each technician their own tools including a general-purpose multimeter. People will take care of their own tools. They can share the specialized tools.

When to select a Fluke 773

Referring back to Figure 2, the 773 is loosely associated with the 789. Conceptually, they perform the same tasks of receiver and transmitter in a 4-20 mA loop.

The 773 has the advantage of being able to measure the loop current without opening the wire; no screwdriver. Like the T6-1000 Pro, it can measure current without inserting the meter in series with the circuit. This has a distinct time advantage as the measurement can be performed in seconds.

The 773 also contains a hardwired 4-20 mA transmitter and receiver. These functions are still required if the technician is to half-step the equipment to eliminate suspect faults from the sensor, cable, or PLC.

When to select a Fluke 725

The 725 is the most specialized of the featured meters.

  • It is designed to interface with a variety of IA analog sensors and actuators.

  • The 4-20 mA loop transmitter and receiver are present similar to the 773 and 789. The 725 has the ability to measure as well as simulate RTDs (Pt100 to Pt1000) as well as thermocouples (E, N, J, K, T, B, R, S, L and U).

  • The 725 will interface with a variety of 750P pressure measurement modules such as the FLUKE-750P07. A representative connection example from the Fluke 725 datasheet is included as Figure 3.

In fairness, this brief description undersells the 725, as it is designed as a process calibrator. For example, consider a transmitter that accepts a Type K thermocouple and outputs a 4-20 mA signal. The 725 can be configured to simulate the sensor and verify that the transmitter is responding with the correct current.

Figure 3: Fluke 725 datasheet connection for measuring pressure using an external module.
Figure 3: Fluke 725 datasheet connection for measuring pressure using an external module.1300×739 63 KB

Figure 3: Fluke 725 datasheet connection for measuring pressure using an external module.

Parting Thoughts

Suppose you were part of Fluke’s design team. Would you attempt to build a meter that does it all? Would you build a handheld meter that includes CAT IV protection, a cell phone interface, 4-20 mA current XMTR/RCVR, RTD, and thermocouple. While you are at it, add a comms analyzer for EtherCAT/PROFIsafe, and a thermal imager?

You could certainly try.

However, the cost would be very high, and the instrument would be difficult to use. In fact, it would be unusable to the technician with gloved hands.

A general-purpose instrument such as the 87V survives the decades not because it does it all. Rather, it survives because its limited functions are optimized for the workflow of the technicians on the factory floor.

We reach for the second Fluke meter when the work requires specialized measurement.

About This Author

Aaron Dahlen, LCDR USCG (Ret.), is a Senior Applications Engineer at DigiKey in Thief River Falls. His background in electronics and industrial automation was shaped by a 27-year military career as both technician and engineer, followed by over a decade of teaching.

Dahlen holds an MSEE from Minnesota State University, Mankato. He has taught in an ABET-accredited electrical engineering program, served as coordinator of an electronic engineering technology program, and instructed military technicians in component-level repair.

Today, he has returned to his home in northern Minnesota, completing a decades-long journey that began with a search for capacitors. Read his story here.

Module 2 Pathway: Engineer: Component Selection and Lifecycle Tradeoffs