Weigh something on a scale and a load cell somewhere underneath is doing the actual work. Its shaped metal core bends by a fraction of a thousandth of an inch, gauges glued to that core register the bending, the bridge behind them produces a voltage, and a certificate written against known weights finishes the translation into pounds.
Force measurement and weighing are usually treated as the same discipline. They aren't quite, and the differences show up in which specifications a manufacturer bothers to publish.
Force testing tends to be brief and active. You apply a load, capture what happens, and move on. What matters is the sensor's behaviour during the event: linearity across a range, response to a fast change, tolerance of an awkward load path.
Weighing is patient. Something sits on a scale and the number has to stay put — while an operator reads it, while a batch controller decides whether to close a valve, while a check weigher accepts or rejects a package. Nothing is moving, and yet the reading can still wander, because metal held under sustained stress creeps very slightly as it accommodates the load. That is why weighing-oriented sensors publish a creep specification, usually measured over twenty or thirty minutes, and why force-testing products often don't bother. In a two-second pull test, creep is irrelevant. In a silo that has been full since Tuesday, it is the specification that decides whether your inventory figure is real.
Temperature ranges tell a similar story. A sensor compensated across a laboratory band is being sold for laboratory work. One compensated from near-freezing upward is expecting a loading dock, a grain bin, a factory floor in winter — the places scales actually live.
The S-type or S-beam shape belongs to this world. Load enters through threaded ends at top and bottom, travels through an S-shaped flexure, and the same sensor works pulled or pushed. It is probably the most widely produced load cell geometry in existence, which has a pleasant consequence: the volumes involved mean S-beams frequently offer better published accuracy at lower cost than specialised shapes made in small numbers. You find them in conveyor scales, check weighers, counting scales, hanging and crane scales, tank and hopper weighing, packaging lines, and test stands where a straightforward in-line pull or push is all that's needed.
The electrical part is quick. The mechanical part is where S-beams reward attention, because this geometry is more sensitive to how it is attached than most.
Signal. Feed the bridge its 10 VDC and it becomes capable of answering. Weight bends the flexure, the gauges alter their resistance accordingly, and what had been a balanced circuit now offers up a few thousandths of a volt. That output is a proportion of the supply, which is why sensitivity appears as volts per volt — and why a larger figure is genuinely worth having, since a bigger signal sits further clear of noise and asks less of the amplifier behind it. Conditioning and the stored certificate complete the chain. Whatever supply the certificate assumed is the supply you need to be running.
Why the attachment hardware is part of the instrument. An S-beam measures force applied along its axis through its threaded ends. Anything else the mounting introduces — a bending moment from a rigid bracket, a side load from a misaligned pull, torsion from a fitting tightened against a shoulder — is error the sensor cannot separate from real load. Published installation guidance is emphatic: force must be centrally aligned through the middle of the cell, and rod ends, swivels or clevises exist precisely to let the load find that line rather than forcing the sensor to accept whatever angle the structure provides.
Three installation mistakes worth naming. Over-tightening the fittings, which can damage the cell rather than secure it. Allowing a load button or rod end to touch the central beam — the beam has to move freely for the sensor to work, and contact there quietly short-circuits part of the load path. And mounting to a surface that isn't clean and genuinely flat, since a base that rocks or twists puts a moment into the flexure before any load is applied.
Creep, and why it appears on weighing datasheets. Hold a load cell under constant load and its output drifts slightly as the metal accommodates the stress; remove the load and it needs time to recover. Specified over a fixed interval, this tells you how much a reading will wander while nothing is happening. For anything where the number is read some time after the load settles — a filled hopper, a hanging scale, a batch weight held for approval — creep is a specification that deserves reading.
Direction and calibration. An S-beam works in both directions mechanically, but the load paths differ between pulling and pushing, so the certificates differ too. A compression calibration documents compression. If your application hangs a load from the cell — which is how a great many S-beams are used — tension calibration is a separate thing to specify rather than assume.
Specifying for a weighing application asks slightly different questions from specifying for a test bench. Our application engineers work through both regularly — describe what you're weighing and how, and we can point you to the right configuration.
Establish whether load hangs or rests. This is the first fork, because it determines both the calibration you need and the hardware around the sensor. A suspended load pulls the cell in tension and needs fittings that let it align itself; a load resting on the cell compresses it and needs a stable, flat seat. Many installations do one or the other exclusively, and knowing which saves specifying for both.
Budget for the mounting hardware as part of the system. Rod ends, swivels, clevises and load buttons are not accessories on an S-beam — they are what allows the load to arrive along the measuring axis instead of at whatever angle the structure happens to impose. Leaving them out is one of the most reliable ways to turn a well-specified sensor into disappointing data.
Size capacity to the working load, allowing for what else arrives. Put your normal weight comfortably inside the range so resolution stays useful, then think about dynamic additions: material dropping into a hopper, a load swinging as a crane stops, a package landing on a check weigher. Those transients count against the safe overload rating, and on conveyor and filling applications they can be a significant fraction of the static weight.
Read the temperature specifications against the real installation. A compensated range tells you where the published accuracy holds, and weighing equipment often lives somewhere less hospitable than a laboratory. Confirm your seasonal extremes fall inside it, and use the published drift coefficients to estimate what a temperature swing does to the reading rather than discovering it on a cold morning.
Check creep if the number will be read at leisure. Where a weight has to hold steady for minutes rather than seconds — approval, inspection, batch control — the creep specification is more relevant than linearity. Where the reading is taken as the load arrives, it hardly matters.
Then material, environment and readout. Aluminium keeps lower-capacity units light and inexpensive; stainless takes over where capacity or surroundings demand it. On protection, sealing of this kind copes with the dust and damp of ordinary industrial life, but pressure washing and chemical exposure sit outside it and are worth raising with us separately. And decide what reads the sensor: an amplifier signal conditioner module, or a digital display with setpoints, alarms, analog output or logging — setpoints in particular being what turns a scale into a filling or check-weighing system. Where a spare cell has to drop into a running scale at short notice, Cal-Teds plug and play means it arrives already knowing its own calibration.
Tell us the weight range, whether the load hangs or rests, what the surroundings are like, and how the reading gets used, and we'll specify it with you. Stock capacities are available for prompt shipment, with educational pricing for schools and universities.
SBO Series Load Cell Applications.
The Transducer Techniques SBO Series S-type load cells, designed for both tension and compression applications, are versatile devices used for precision weight and force measurements.
- Conveyor Scales: SBO Series load cells are commonly used in conveyor scales to measure the weight of bulk materials or products as they move along a conveyor belt. This is essential in industries such as agriculture, mining, and logistics for accurate inventory control and process optimization.
- Check Weighers: Check weighers are used in food processing, pharmaceuticals, and other industries to ensure that packaged products meet specified weight requirements. SBO Series load cells are integrated into these systems to provide precise weight measurements.
- Counting Scales: Counting scales are used in inventory management and parts counting applications. SBO Series load cells contribute to accurate counting by measuring the weight of individual items and converting it into quantity.
- Materials Testing: These load cells are utilized in materials testing laboratories for a wide range of tests, including tensile and compressive testing of materials such as metals, plastics, rubber, and more. They provide precise force measurement data.
- Industrial Automation: In industrial automation systems, SBO Series load cells are integrated into machinery and equipment for monitoring and controlling forces in various manufacturing processes. They ensure quality control and process efficiency.
- Packaging: The packaging industry uses SBO Series load cells to monitor and control the filling and sealing processes of packages. Ensuring accurate filling and sealing is crucial for product quality and compliance.
- Agricultural Equipment: SBO Series load cells find applications in agricultural machinery and equipment, such as grain bins and silos, to measure the weight of stored agricultural products for inventory management and process optimization.
- Material Handling: In material handling equipment like cranes, hoists, and lifts, these load cells are used to measure the load being lifted or moved. This helps prevent overloading and ensures safe operation.
- Quality Control: SBO Series load cells are integrated into quality control processes across industries to verify that products meet specified weight and force requirements.
- Research and Development: Engineers and researchers use these load cells during product development and testing to evaluate the performance and durability of various products and components.
- Aerospace and Aircraft Testing: The aerospace industry relies on SBO Series load cells for structural testing of aircraft components, ensuring that they meet weight and force specifications for safe operation.
Their versatility and reliability contribute to improved product quality, safety, and process efficiency.
Frequently Asked Questions
What is an S-type load cell, and why is it shaped that way?
The S shape is a flexure with threaded attachment points at top and bottom, so load enters through the ends and travels through the middle of the cell. That geometry does two useful things: it works equally in tension and compression through one sensing element, and it makes the sensor straightforward to install in-line — screw a fitting into each end and the load path runs through the cell. It's one of the most widely produced load cell shapes in the world, which is exactly why S-beams tend to offer strong published accuracy at modest cost.
What capacities does the SBO Series cover?
Ten: 50, 100, 200, 300, 500, 750, 1,000, 2,000, 3,000, and 5,000 lb. That range covers most of what weighing applications call for — check weighers and counting scales at the low end, conveyor and hopper weighing through the middle, and crane, hoist and tank applications at the top.
Why does the SBO have a 3 mV/V output when your other load cells are 2 mV/V?
The S-beam geometry strains its gauges more efficiently for a given load, which produces a stronger signal. At 3 mV/V and 10 VDC excitation, full capacity delivers around 30 mV rather than the 20 mV a 2 mV/V sensor gives — fifty percent more signal for the same supply. That's a practical advantage, not just a number: a larger signal sits further above electrical noise, tolerates longer cable runs better, and needs less amplification, which means less amplified noise arriving at your display.
How accurate is the SBO Series?
Nonlinearity is 0.05% of rated output, hysteresis 0.03%, nonrepeatability 0.02%, and zero balance 1.0%. Those are the tightest published accuracy figures across our load cell range — better than several of our specialised precision products. The reason is production scale rather than anything exotic: the S-beam is the most common load cell form factor there is, and volume manufacturing of a well-understood geometry delivers accuracy that low-volume specialty shapes struggle to match at the same price.
What is the creep specification, and why does the SBO publish one?
Creep is 0.03% of rated output over 20 minutes. It describes how much the reading drifts while a constant load simply sits there, as the metal gradually accommodates sustained stress. This is a weighing specification, and the SBO publishes it because weighing applications need it — a hopper that stays full, a batch weight held for approval, a scale someone reads a few minutes after loading. In a brief force test creep is irrelevant, which is why force-testing products often don't quote it. If your reading is taken at leisure rather than on arrival, this is a number worth knowing.
What is the SBO made from?
Anodized aluminum on the 50 through 1,000 lb models, and 17-4 PH heat-treated stainless steel on the 2,000 through 5,000 lb models. Aluminum keeps the lower capacities light and cost-effective while still straining enough to produce good signal; the higher capacities need the strength that precipitation-hardening stainless provides. Bonded foil strain gauges throughout, sealed for protection in industrial environments.
What thread sizes does the SBO use?
Three, stepping up with capacity: 3/8-24 on the 50 through 300 lb models, 1/2-20 on the 500 through 3,000 lb models, and 5/8-18 on the 5,000 lb model. Confirm the thread for your specific capacity before ordering rod ends or fittings, and note that changing capacity within the series may change the thread — so hardware bought for one model won't necessarily transfer to another.
Is the SBO calibrated for tension or compression?
Compression calibration is included as standard, with tension calibration available as the TC-CAL option. That's worth flagging deliberately, because a great many S-beam installations hang a load from the cell — crane scales, hanging scales, suspended hoppers, tension test setups. If yours is one of those, specify tension calibration at order time. The load paths genuinely differ between pulling and pushing, and a compression certificate documents compression alone.
What temperature range is the SBO compensated for?
15° to 115°F compensated, with a safe operating range of −65° to 200°F. That compensated band is noticeably different from our test-and-measurement products, which typically start at 60°F — and it reflects where weighing equipment actually lives. Loading docks, grain bins, unheated warehouses and outdoor installations routinely see temperatures well below a laboratory's comfort zone, and the SBO is compensated down to near freezing for exactly that reason.
Can I get the SBO with the plug-and-play TEDS option?
Yes, OPT-TEDS stores the unit's calibration data at the connector so a compatible instrument reads and applies it automatically. On multi-scale operations where cells get swapped between stations, or where a spare is kept on the shelf against downtime, that's genuinely useful — the replacement carries its own calibration rather than requiring someone to find the right numbers and enter them correctly under time pressure.
Questions From The Field
Do I really need rod ends or swivels, or can I bolt the cell straight in?
On an S-beam, treat them as part of the sensor rather than as optional hardware. The cell measures force along its axis, and a rigid bracket at each end forces it to accept whatever angle your structure happens to impose — that misalignment arrives as a bending moment the sensor cannot distinguish from real load. Rod ends, swivels and clevises exist to let the load find the axis instead. Installation guidance is consistent on this point: force must be centrally aligned through the middle of the cell, and self-aligning fittings are how that gets achieved in a real structure.
I fitted rod ends but my readings are still poor.
Check three things, all of them common. First, clearance — if a rod end or load button is touching the central beam, the beam can't move freely and part of your load path bypasses the sensing element entirely. There must be a gap. Second, tightening — over-torquing the fittings can damage the cell rather than secure it, and it's easy to do by feel. Third, the mounting surface, which needs to be clean and genuinely flat; a base that rocks or twists puts a moment into the flexure before any load arrives.
My hopper reading drifts downward over the first half hour after filling.
Some of that is expected and specified. Creep on the SBO is 0.03% of rated output over 20 minutes — the metal accommodating sustained stress — so a small settling drift after a load is applied is normal sensor behaviour rather than a fault. Calculate what that figure predicts for your capacity and compare it against what you're seeing. If your drift is substantially larger, look at the structure instead: material settling in the hopper, a support flexing, piping or conduit slowly taking up load, or a temperature change in the surroundings.
Should I choose an SBO or one of your precision test load cells?
Ask what shape of installation you have. If the load arrives in-line and can be attached through threaded ends — hanging, pulling, or pressing straight down the axis — the SBO is likely both the more accurate and the more economical choice, since its published figures are the tightest in our range. Our specialised button, column and through-hole designs exist for installations the S-beam can't serve: no room for a beam, a bolt that has to pass through the sensor, capacities beyond 5,000 lb, or dynamic events needing very high frequency response. Geometry usually decides this, not accuracy.
Can I use one SBO under a tank, or do I need several?
It depends on whether the tank is suspended or supported. A hanging vessel on a single point can use one cell, provided nothing else carries load — and that proviso does most of the work, since piping, conduit and flexible connections routinely take a share of the weight and quietly corrupt the reading. A tank resting on legs needs a cell under each support, with their outputs summed, because load distributes between them and no single point sees the total. Tell us the arrangement and we can advise on the count and how to sum them.
My crane scale reads high when the load swings. Is that real?
Yes, and it's genuine force rather than sensor error. A swinging load accelerates, and acceleration adds to the static weight — the cell reports what's actually pulling on it at that moment, which is more than the mass alone. Let the load settle before taking a reading, use display averaging or a peak-hold-free steady mode where available, and size the cell with headroom for those transients, because a swing arriving at the end of its arc can take you closer to the overload rating than the nominal weight suggests.
Does the thread size change if I move to a different SBO capacity?
It can. The series uses 3/8-24 up to 300 lb, 1/2-20 from 500 through 3,000 lb, and 5/8-18 at 5,000 lb, so a capacity change may or may not cross a thread boundary. Check before ordering, because rod ends and fittings bought for one model won't necessarily fit another — and if you're specifying a new installation where the capacity might be revised later, choosing a capacity that shares a thread with its neighbours can save re-buying hardware.
My scale was accurate in summer and reads differently in winter.
First confirm your installation stays inside the compensated range of 15° to 115°F, since accuracy figures only apply within it — unheated warehouses and outdoor installations can drop below that in a cold snap. Within the band, use the published drift coefficients to estimate what your seasonal swing should produce and compare it against what you're seeing. If the difference is much larger than predicted, look at the structure rather than the sensor: thermal expansion in a frame or vessel can put real load into a cell, and that shows up as a seasonal shift that no amount of recalibration will fix.