(Fluke: Everett, WA) -- Morehouse Instrument Co. is a leader in torque and force calibration. The company provides government and private labs across the country with reliable calibration equipment, services, and training.

Based in York, Pennsylvania, Morehouse has been in the calibration business for more than 100 years. For decades, the company has relied on Fluke multimeters to uphold its high standards when testing and calibrating customer equipment such as load cells.

Load cells are transducers that convert force into electrical signals. They are present in a wide range of tools and devices, from industrial scales to prosthetics. Over time, these transducers drift and need to be calibrated. That’s where the expertise of Morehouse metrologists comes in.

Morehouse incorporates Fluke’s 8588A reference multimeter.

With the 8588A reference multimeter, Morehouse:
• Decreased measurement uncertainty for ratio metric measurements by nearly 50%, resulting in improved traceability
• Built a cutting-edge, automated solution for force calibration
• Gave customers an affordable and easy-to-operate solution for force applications

Challenges

Load cell output can be difficult to measure, since it requires taking multiple measurements simultaneously. Metrologists must capture both output voltage (mV) and excitation voltage (DCV) to calculate a ratio of the two, expressed as millivolts per volt (mV/V). Additionally, they need to use two separate multimeters—one to measure output and one to measure excitation voltage—to capture these voltages.

For decades, Morehouse metrologists used an Agilent/HP 3458A, and later a Fluke 8508A, both 8.5-digit multimeters, to take load cell measurements. Previously, the lab had tried to move from an HP 3458A to a Schlumberger 7061, which died and couldn’t be repaired. While the remaining multimeters provided the necessary uncertainty rating for force calibration, both legacy devices had their shortcomings when taking ratio metric readings.

Beyond having to stack two 3458As to take a single reading, calibration times were extremely long. And the 8508A was “really slow to update,” Morehouse CEO Henry Zumbrun says. “I think there was some additional error on that part because you can set them faster, but then we lose uncertainty.”

As a result, calibration became cumbersome. The team was also limited in what kinds of data they could capture, because their legacy multimeters often failed to pick up short pulse events and transients.

“So when Fluke released the 8588A reference multimeter, the Morehouse team got excited because the specs were good,” Zumbrun says. Sure enough, the 8.5-digit multimeter alleviated many of the speed, accuracy, and measurement issues associated with the legacy devices. It was also easy for technicians to use, thanks to the device’s intuitive menu system.

Zumbrun says, “Now we are thrilled, as we found a meter that exceeds the older Schlumberger model everyone loved.”

Implementation

With dual inputs on the front and back, the 8588A eliminates the need for multiple devices to capture ratio metric readings and lets metrologists measure load cell output ratios with just one device. Although the 8588A wasn’t designed specifically for load cell calibration, its versatility, accuracy, traceability, ease of use, and easy programmability made it perfect for Morehouse’s unique application.

“It seemed like a good fit, so we ended up buying four, internally, for ourselves,” Zumbrun says.

Today, the team uses the 8588As in the Morehouse laboratory to calibrate customer equipment that needs DC measures and ratio metric measurements. They also use the multimeters to calibrate 4-24 mA and 0-10 VDC load cells, load cell simulators, and to conduct deadweight torque and force calibrations.

With the 8588A, Morehouse saw a significant decrease in measurement uncertainty during calibration.

As a long-scale, high-precision multimeter (maintaining measurements at around 10 ppm), the 8588A also provided superior accuracy, giving it an edge over other multimeters Morehouse had worked with.

“Morehouse customers expect traceability to make a ratio metric measurement,” says Zumbrun. “This is probably the best indicator out there for that.” The 8588A halved the previous measurement uncertainty rating from 20 ppm to 10 ppm at the load cell’s full-scale output.

Because of these benefits, the 8588A became the muscle behind the company’s new automated force calibration system (AFCS) for data acquisition when a customer chooses not to send in a meter.

Designed to pair with all Morehouse universal calibrating machines (UCMs), the new automated control system can calibrate pressures of up to 4,500 PSI—more than conventional hydraulic and automated controls, which top out at 3,000 PSI. It’s portable, affordable, and offers a range of features that set the AFCS light years ahead of traditional force calibration solutions.

Results

Not only did Morehouse improve efficiency in its own lab with the 8588A, but it also helped customers establish a traceable measurement chain for mV/V that has far lower measurement uncertainty than most other systems available. As an added bonus, there have been substantial time and money savings in calibration turnaround time (TAT).

Prior to automation, a Morehouse technician would have to manually operate the Morehouse universal calibrating machine. Each exercise cycle would take 5–6 minutes, and each test point would take 90–120 seconds to reach the force point, control it, and record the reading. To further complicate things, sometimes a run would need to be scrapped if a test point was exceeded.

Automation eliminates the possibility of overshooting the test point. A 10-point calibration that took 35 minutes by hand now only takes about 26 minutes (assuming a dwell time of at least 30 seconds at each force point). Overall, Morehouse has seen an increase in throughput by about 50% for automated calibrations, since the only thing technicians need to do is set up the instrument. This frees them to do other tasks in the meantime, like paperwork or preparing the next instrument for calibration while the machine does the work.

Once out of beta testing, the automated force calibration system was incorporated into the laboratories of more than a dozen satisfied customers. In the past few months, there has been “very little noise on the system, and our customers have been happy,” Zumbrun says. “We are hoping 2026 will see a massive rollout of more automated force machines sold with the Fluke 8588A as part of an ongoing partnership between Fluke and Morehouse.”

The automated system adds an extra layer of speed and traceability to force calibration for a wide variety of customers. With the Fluke 8588A reference multimeter at its core, Morehouse offers buyers a precise, affordable, and easy-to-operate system for force calibration. Measurements such as mV/V, DCV, and mA that are made possible by the 8588A are traceable to SI through Fluke’s primary standard laboratory.

In collaborating with Fluke, Morehouse was able to create a solution that directly addresses customer needs and cements its legacy as a leader in the field of force calibration.