A load cell converts mechanical force into an electrical signal. Most people first meet load cells as weighing devices, but weight is only one thing they measure — a load cell reports force, and force can be pushing, pulling, or alternating between the two.
That last point is what separates a universal load cell from the rest of the category. A dedicated compression load cell is designed to be pushed, and a dedicated tension load cell to be pulled. A tension and compression load cell handles both directions through a single sensing element, producing a positive signal in one direction and a negative signal in the other, with a continuous response through zero. For any test that loads and unloads a sample, cycles a mechanism, or reverses direction mid-run, that saves you from either buying two sensors or accepting a compromise on one.
Inside, the construction is the same family of technology used across the industry. Bonded foil strain gauges are attached to a precisely machined flexure and wired into a Wheatstone bridge. Force deflects the flexure by a few thousandths of an inch, the gauges deform and change resistance, and the bridge turns those resistance changes into a proportional millivolt output. The flexure geometry — and the material it's machined from — is what tunes a given design toward a particular capacity range, stiffness, and frequency response.
Material choice follows capacity and environment. Anodized aluminum is light, easy to machine into compact geometries, and well suited to lower capacities where a compact sensing element still strains enough to produce good signal. Alloy steel offers the highest strength and output for general-purpose work. Stainless steel is chosen when higher capacity demands more strength in the same compact envelope, or when corrosion resistance matters. It's common for a single miniature series to transition from aluminum at its lower capacities to stainless steel at its upper ones for exactly this reason.
Common configurations include compression, tension, universal tension-and-compression, S-type (S-beam) designs for in-line push and pull, bending and shear beam designs for scales and conveyors, and through-hole or load washer designs that allow a shaft or bolt to pass through the sensor. Miniature universal designs are frequently specified in universal testing machines, medical device and pharmaceutical equipment, semiconductor assembly, dental and biomechanics research, robotics end-effectors, and product development labs — anywhere bidirectional force has to be measured accurately at modest capacity in a small package.
The measurement chain is worth understanding in both directions, because bidirectional sensing is where a lot of practical questions come from.
The bridge at rest. With no load, the four strain gauges sit at their nominal resistance and the Wheatstone bridge is balanced, producing near-zero output. Real sensors have a small residual offset, published as zero balance, which your instrumentation zeroes out during setup.
Under compression. Pushing on the load cell deflects the flexure one way. Gauges positioned on surfaces that go into compression drop in resistance while gauges on surfaces going into tension rise. The bridge unbalances in one direction and produces an output of one polarity.
Under tension. Pulling reverses the flexure's deflection, reverses which gauges are stretched and which are compressed, and produces an output of the opposite polarity. This is the mechanism behind a universal load cell: nothing switches or reconfigures, the bridge simply swings the other way, which is why a properly zeroed universal cell reads continuously through zero without needing to be re-zeroed when direction changes.
Signal size depends on excitation. Output is specified in mV/V because the sensor modulates the excitation voltage applied to the bridge. At 2 mV/V and 10 VDC excitation, full capacity produces roughly 20 mV. Higher sensitivity means a stronger signal for the same excitation, which generally makes a sensor more forgiving of cable runs and electrical noise.
Conditioning and digitizing. That millivolt signal is amplified, filtered, and converted for display or recording. Filtering choice is a real trade-off: more filtering yields a cleaner reading but slower response, which matters when the force you're measuring is changing quickly.
Calibration in each direction. Known reference forces are applied and outputs recorded to establish the force-to-signal relationship. Because the load path and fittings differ between pushing and pulling, calibrating a load cell in compression versus tension produces two separate relationships. A cell shipped with compression calibration has a documented compression relationship; tension calibration is a distinct operation, which is why it's typically offered as a specified option rather than assumed.
Where dynamic limits come from. Every load cell has a natural or ringing frequency — the rate at which its flexure oscillates freely when struck by a sudden force. Stiffer, higher-capacity designs ring higher; more compliant, lower-capacity designs ring lower. A widely used rule of thumb is to keep the frequency content of what you're measuring to somewhere between one-fifth and one-tenth of the sensor's natural frequency. Beyond that, the output can distort in both amplitude and timing, and sharp impacts will show up in your data as a decaying oscillation riding on the real signal.
Temperature deserves a mention too. Good load cells publish both a compensated temperature range, within which stated accuracy holds, and drift coefficients for output and zero. Those coefficients let you estimate expected error across a known temperature swing rather than guessing at it — useful on long test runs where the room or the equipment warms up.
Selecting the right load cell and instrument for a force measurement application is something our application sales engineers do every day, and we'd rather help you get it right up front than sort it out after delivery. It generally comes down to your budget, your application, what stage that application is in, and how soon you need it.
On bidirectional work specifically, the most common mis-step we see is over-specifying capacity. It's natural to size a sensor to the largest force it could conceivably see in either direction, but on a universal cell that decision costs you twice: resolution suffers across the whole working band, and it suffers in both directions at once. Sizing to the force you'll actually spend your time measuring, then confirming your genuine worst case still sits inside the safe overload rating, usually produces better data than buying headroom you'll never use.
The second thing worth settling early is what the sensor will be attached to. On small-capacity work, adapters, couplings, and fixture hardware are not negligible — they can represent a real fraction of rated capacity, and they behave differently depending on whether the cell is being pushed or pulled. Zeroing the system in the exact orientation and configuration you'll test in, with the fixture already installed, removes that from your measurement instead of leaving it buried in it.
Sometimes, though, the deciding factor isn't the sensor at all — it's how quickly the whole system has to be up and running. National Geographic needed to measure the force of a strongman pulling a semi tractor trailer, with filming scheduled for the next day. Accuracy and speed of setup drove that decision, so we supplied an HSW-20k load cell with the Cal-Teds smart plug and play option paired with a DPM-3 load cell meter. Because the meter reads the EEPROM chip in the Cal-Teds option and populates an IEEE 1451.4 template 33, the system calibrated itself the moment the two were plugged together — an inexpensive system that was ready to shoot on schedule.
For your own selection, here's what to define:
Budget and timing. A limited budget or a next-day need narrows the field quickly. We stock standard products for next-day shipping and offer educational discounts.
Loading direction and behavior. Tension, compression, or both? Static or dynamic? A universal tension and compression cell covers bidirectional testing in one sensor. For dynamic work, roughly doubling the capacity you would choose for the same force applied statically is a sensible starting point, and natural frequency should be checked against the frequency content you actually need to capture. Also decide whether load is applied in-line or whether the sensor will see extraneous side loads.
Capacity and headroom. Size to your working force for resolution, then confirm your realistic worst case sits within the safe overload rating. Where your forces land near a boundary between two capacities, the trade is resolution at the low end against overload margin and higher natural frequency at the high end — a conversation worth having rather than a coin flip.
Mounting and integration. Threaded, flanged, or a through hole or compression load washer design that lets structure pass through the sensor? Fixture geometry determines whether force reaches the sensing element cleanly, and misalignment is one of the most common causes of disappointing real-world accuracy.
Environment and materials. Laboratory, production floor, outdoors, or submerged? Aluminum, alloy steel, and stainless steel each bring different strength and corrosion characteristics, and for extended outdoor, marine, or underwater service we recommend a hermetically sealed load cell rather than relying on material choice alone.
Performance specifications. Define the overall accuracy you need and work backward through output, bridge resistance, nonlinearity, hysteresis, nonrepeatability, and frequency response. Nonrepeatability in particular is easy to overlook and often the spec that matters most in production testing, where you're comparing part to part.
Options. Connectors, non-standard cable lengths, high-temperature construction, or the Cal-Teds plug and play smart option if you'll be swapping sensors between instruments.
Instrumentation. From a precision power supply to an amplifier signal conditioner module to a digital display with alarms, analog output, or data logging, the readout side deserves as much thought as the sensor.
If you're specifying a load cell for the first time, this can feel like a lot at once. It isn't for us — it's the part of the job we enjoy. Tell us what you're measuring and we'll help you get from selection through installation and setup.
MDB Series Load Cell Applications.
The Transducer Techniques MDB Series load cell with universal tension and compression capabilities and a range of seven capacities from 0 to 2.5 lbs. to 0 to 100 lbs. is a versatile force measurement device suitable for a wide range of applications across various industries. Here are some specific applications where these load cells can be used:
- Medical Devices and Equipment: These load cells are commonly used in the medical field for applications such as measuring the force required to operate medical devices like syringes, infusion pumps, and orthopedic equipment. They ensure the safety and effectiveness of medical treatments and procedures.
- Pharmaceutical Manufacturing: In pharmaceutical manufacturing, these load cells are used to measure and control the compression force applied during tablet and pill manufacturing processes, ensuring the consistency and quality of pharmaceutical products.
- Microelectronics and Semiconductor Manufacturing: The load cells are utilized in semiconductor manufacturing equipment for precision force control during processes like wafer probing, die bonding, and wire bonding. They ensure the accuracy and reliability of microelectronic components.
- Materials Testing: These load cells are suitable for materials testing applications, including tensile, compression, and flexural testing of materials such as polymers, composites, and biomaterials in research and quality control settings.
- Aerospace and Aviation Testing: In the aerospace industry, these load cells can be used to measure forces in small components and assemblies during testing and research, contributing to the development and safety of aircraft and spacecraft.
- Dental Equipment: Dental laboratories and equipment manufacturers use these load cells to measure the forces applied during procedures like orthodontic adjustments and dental implant installations, ensuring precision and patient comfort.
- Robotics and Automation: These load cells are valuable in robotics and automation applications to measure and control forces exerted by robotic arms, grippers, and end-effectors. They help achieve precise and controlled movements in robotic systems.
- Biomechanics and Rehabilitation: Researchers and practitioners in biomechanics and rehabilitation use these load cells to assess forces and pressures on the human body during activities like gait analysis, ergonomic evaluations, and the development of assistive devices.
- Product Development: These load cells are used in the development and testing of various products, including handheld tools, consumer electronics, and mechanical components, to evaluate the forces applied during normal operation and ensure product reliability.
- Educational Laboratories: Educational institutions use these load cells in physics and engineering laboratories to teach students about force measurement principles and conduct experiments related to mechanics and materials science.
- Small-Scale Manufacturing: Small-scale manufacturing operations that require precise force control, such as jewelry making and watch manufacturing, can benefit from these load cells to ensure high-quality and precise assembly.
- Custom Machinery: The load cells can be integrated into custom-built machinery and equipment for specialized manufacturing and testing applications that demand precise force measurement and control.
- Packaging and Testing of Miniature Components: In industries like microelectronics and microfabrication, these load cells are used to test and package miniature components, ensuring their functionality and reliability.
These applications highlight the versatility and precision of the Transducer Techniques MDB Series load cells, which can provide accurate force measurements in various industries and scenarios, particularly where small-scale force measurements are critical for product quality and performance.
Frequently Asked Questions
What makes the MDB Series a "universal" load cell?
The MDB Series is described as universal because a single unit measures force in both directions — pulling (tension) and pushing (compression) — through the same sensing element, rather than requiring you to buy a dedicated cell for each direction. For applications that cycle between pull and push, like a materials test that loads and unloads a sample, that means one sensor covers the whole test rather than two.
What capacities does the MDB Series come in?
The MDB Series is offered in seven capacities: 2.5, 5, 10, 25, 50, 75, and 100 lb. Having seven steps across that range lets you size the cell close to your actual working force instead of over-specifying, which preserves resolution and accuracy at the loads you'll really be measuring.
Why are some MDB models made from anodized aluminum and others from stainless steel?
The MDB Series uses anodized aluminum for the 2.5 through 50 lb capacities and stainless steel for the 75 and 100 lb capacities. Aluminum is light and easy to machine into a compact sensing element, which suits the lower capacities well, but it can't carry as much stress as steel — so the higher-capacity MDB models move to stainless steel to handle the greater load while keeping the same compact form factor and one-ounce weight.
What are the MDB Series' accuracy specifications?
The MDB is specified at 0.05% of rated output for nonlinearity, hysteresis, and nonrepeatability alike, with a zero balance of 1.0% of rated output. The nonrepeatability figure is worth noting specifically: it tells you how consistently the cell returns the same reading when the same load is reapplied, which matters as much as raw accuracy in quality-control and production-test work where you're comparing part to part.
What is the MDB Series' rated output and excitation voltage?
The MDB has a rated output of 2 mV/V nominal with a 350 ohm nominal terminal resistance, excited at 10 VDC. The 2 mV/V rating produces a stronger signal than lower-sensitivity cells at the same excitation, which generally makes it a little more forgiving to pair with instrumentation and a little less susceptible to noise on the signal line.
What cable comes with an MDB load cell?
Each MDB ships with an AMX-4 10-foot mating cable included, so you have a ready connection to your instrumentation out of the box rather than needing to source or terminate a cable separately as a first step.
Why does the MDB's deflection change depending on which capacity I order?
Deflection across the MDB range runs from 0.004 inches up to 0.012 inches at rated output, varying by capacity. This is a normal characteristic of strain-gauge design: the sensing element has to flex enough to generate a usable signal, and the amount of flex that requires differs across capacities. It's worth knowing if your fixture or test setup is sensitive to how much the sensor itself moves under load.
What is the MDB Series' natural ringing frequency, and why is it listed as a range?
Natural ringing frequency across the MDB Series spans roughly 575 Hz to 3300 Hz, varying by capacity — the stiffer, higher-capacity models sit at the top of that range. Natural frequency is the rate at which the sensor oscillates on its own when hit with a sudden force, and it's listed per capacity because it directly bounds how fast a changing force the cell can track cleanly.
How much does temperature affect an MDB load cell's readings?
The MDB publishes both drift figures: output drift of 0.005% of load per °F and zero drift of 0.005% of rated output per °F, within a compensated range of 60° to 160°F. Its safe operating range extends from −65° to 200°F. Because the drift is specified rather than just implied, you can actually calculate expected error for a known temperature swing rather than guessing at it.
Where is the MDB Series typically used?
The MDB is a common fit in medical device and pharmaceutical equipment, semiconductor and microelectronics assembly, materials and biomechanics testing, dental equipment, robotics and automation end-effectors, aerospace component testing, and product development labs. The through-line is small-scale, precise force measurement in applications where the force being measured is well under a few hundred pounds but the accuracy requirement is high.
Questions From The Field
How fast a changing force can I actually measure with an MDB before the readings become unreliable?
A widely used rule of thumb is to keep your measured force frequency to roughly one-fifth to one-tenth of the load cell's natural frequency. With the MDB's natural frequency spanning about 575 Hz on the lowest capacity up to 3300 Hz on the highest, that puts realistic usable measurement bandwidth in the tens to low hundreds of hertz on a low-capacity unit, and higher on the stiffer models. Push past that and the signal can start to distort in both amplitude and timing.
My MDB data shows an oscillation or "ringing" right after impact — is the load cell broken?
Almost certainly not. A sudden force sets the sensing element oscillating at its natural frequency, and if your test involves a sharp impact or step change, that ringing shows up in the data as a decaying oscillation superimposed on the real signal. The fixes are usually on the test side rather than the sensor side: apply the load less abruptly if the application allows, add filtering appropriate to your actual signal bandwidth, or move to a stiffer, higher-capacity model with a higher natural frequency.
Can I use a stainless steel MDB model in a washdown or corrosive environment?
Stainless steel is generally chosen for better corrosion resistance than aluminum, which is one reason the higher-capacity MDB models use it — but material alone isn't the same as a sealed, washdown-rated enclosure, and the MDB's published specs don't include an ingress protection rating. If your environment involves washdown, spray, humidity, or chemical exposure, contact us with the details before assuming the stainless models will hold up; a hermetically sealed cell may be the better answer.
Can I replace the included AMX-4 cable with a longer run without affecting my readings?
Longer cable runs add resistance in the excitation leads, which can cause a small drop in the voltage actually reaching the bridge and a corresponding scaling error in your readings — the effect grows with cable length. If you need a longer run than the included 10-foot AMX-4, talk to us about the right cable and whether your instrumentation supports remote sensing to compensate for the drop, rather than simply splicing in extra length.
Do I need to re-zero my MDB when I switch between pulling and pushing during a test?
Not normally — the MDB is a universal cell, so the bridge responds continuously through zero in both directions and produces a positive or negative signal accordingly. What matters more is that the cell was zeroed correctly at the start with the fixture in place and no test load applied, so both directions are referenced to the same true zero. If you're seeing an offset that only appears in one direction, that usually points to something mechanical in the fixture rather than the sensor.
My MDB readings drift over a long test run — how much of that is temperature?
You can estimate it directly from the published drift specs: 0.005% of load per °F for output and 0.005% of rated output per °F for zero. Multiply those by your actual temperature change over the run and compare the result to the drift you're seeing. If your measured drift is much larger than that calculation predicts, temperature isn't the whole story — look next at excitation stability, connection quality, and whether anything in the fixture is creeping or settling under sustained load.
My readings won't repeat consistently between identical tests — what should I look at?
The MDB's nonrepeatability spec is 0.05% of rated output, so scatter noticeably larger than that generally points to the setup rather than the sensor. The usual culprits are a fixture that isn't clamping identically every cycle, off-axis or side loading that varies between runs, inconsistent loading speed, or the sample seating differently each time. Standardize the fixture and the loading procedure first before suspecting the cell.
Should I order a lower-capacity aluminum MDB or a higher-capacity stainless one if my forces sit right around 50 to 75 lb?
If your peak forces genuinely approach 50 lb, stepping up to a 75 lb stainless model gives you meaningful headroom against the 150% safe overload limit and a higher natural frequency for dynamic work, at some cost in resolution at the low end of your range. If your forces sit comfortably below 50 lb with only rare excursions, the 50 lb aluminum model will give you better resolution. Tell us your typical and worst-case loads and we can help you weigh the tradeoff for your specific test.