A load cell reports force as voltage. Load strains a machined element, bonded foil gauges riding on it change resistance, a Wheatstone bridge converts that into a millivolt signal, and a certificate written against reference standards converts the millivolts into pounds.
Notice what the bridge is actually doing: comparing four resistances against each other and reporting the imbalance. The changes it resolves are extraordinarily small. That sensitivity is the whole point of the instrument, and it is also its vulnerability — because anything that quietly adds a conductive path across those resistances produces an imbalance the bridge cannot distinguish from force.
Moisture is exactly that. Which is why load cells in demanding environments usually do not fail; they drift.
The failure arrives slowly and looks like something else. There is rarely a moment when a moisture-affected sensor stops working. The zero wanders a little. Readings that used to repeat no longer quite do. Someone re-zeroes, and it works for a while. The measurement has already stopped being trustworthy, and nothing about the sensor looks wrong — which is a considerably worse outcome than an obvious failure, because the bad data goes into reports, into process control, into decisions.
A dry environment is not automatically a safe one. The assumption that moisture ingress requires exposure to water is where most of the surprises come from. A cell that is merely sealed rather than hermetic breathes: the air inside expands when the equipment warms and contracts when it cools, drawing in ambient air each cycle, and moisture condenses out of that air inside the cavity. Published guidance on load cell failures lists internal condensation from temperature cycling alongside washdown and cable damage as a route to moisture damage. A sensor that has never been rained on can accumulate water inside it purely by running warm during the day and cooling overnight.
Contamination need not be water at all. Metallic dust, salt-laden air, and corrosive vapours are all conductive or become so, and all of them attack the same thing. A grinding shop and a coastal site pose the same problem by different means.
Hermetic construction exists to close that whole category off, which is why it is specified where the consequences of quiet drift are serious: aerospace and automotive structural testing, food and beverage lines subject to regular washdown, chemical and pharmaceutical manufacturing, marine and offshore installations, wind and hydroelectric plant, and any laboratory work whose results have to stand up years later.
The electrical principle is the same one every strain gauge sensor uses. What separates a hermetic design from a well-protected one is mechanical, and it comes down to a small number of construction decisions.
Signal. The bridge is excited at 10 VDC and delivers 2 mV/V at rated load — a ratio, not a fixed voltage, so roughly twenty millivolts corresponds to full load at any capacity in the range. Signal conditioning and the certificate on file do the rest, with the certificate assuming the excitation voltage it was written at.
The seal is won or lost where the wires come out. This is the part most descriptions skip. Sealing a metal cavity is straightforward; sealing the point where electrical connections pass through the wall of that cavity is not, and published guidance on hermetic construction identifies that connection area as the most common place a hermetic seal fails. A body that is genuinely watertight with a cable entering through a gland or a potted grommet is not hermetically sealed — it is a sealed body with an unsealed doorway. The HSW addresses this with a stainless steel moulded connector system built to resist washdown and most chemicals, so the electrical exit is part of the sealed structure rather than a compromise in it.
Welded construction does not age the way potted construction does. Foam, adhesive and epoxy protection all degrade eventually, and when they do the protection is gone without anything visible having happened. A welded stainless seal does not break down on that timescale. This is the difference between a sensor that is protected when it is new and one that is still protected in year eight, and it is the reason hermetic sealing is worth paying for in installations that are difficult to reach or expensive to interrupt.
Stainless throughout, not just at the top of the range. Every capacity in this series is heat-treated 17-4 PH stainless steel, including the smallest. On several of our other series the lower capacities are aluminum, which is entirely appropriate on a bench and much less so in a chemical plant. Here the material is consistent because the environment, not the load, is what set the specification.
Speed and deflection are published per model. Natural ringing frequency runs from 2,100 Hz at 500 lb up to 9,500 Hz at 50,000 lb, and deflection is 0.003" on the lower capacities and 0.006" on the largest. Both figures come from the specific model rather than the series, so read them from the row you intend to order. Higher-capacity bodies are stiffer structures, which is why the larger models ring faster despite weighing more.
On most force measurement jobs the environment is the last thing considered. On this one it comes first, because it is the reason this class of sensor exists. Everything else follows from an honest description of where the sensor will spend its working life.
Describe the environment as it actually is. Not the design intent — the reality. Is it hosed down, and with what? Is there salt in the air? Are there vapours, coolant mist, conductive dust? Does the equipment run warm and cool overnight? Is the sensor somewhere that would require shutting a line down to reach? Any one of those pushes the answer toward hermetic construction, and the last one often decides it on its own.
Then weigh the premium against the interruption. Hermetic sealing costs more, though the difference narrows considerably at the top of the range. The comparison that matters is not sensor against sensor but the extra cost against what an unplanned replacement involves — the access, the downtime, the recalibration, and the period beforehand during which the readings were drifting and nobody knew.
Settle the direction before you order. The element responds to tension and compression alike, but the certificate is written for one of them. Compression calibration is included and tension is a priced option, tiered by capacity. It is a moment's conversation at enquiry and an irritation afterwards.
Take the mechanical figures from your own model. Thread size, tapped depth, height, weight, deflection and ringing frequency all change across the range, and several change at different points. Height runs from 2.50" to 6.25" and weight from 1.9 lb to 12 lb. Design around the row for the capacity you are buying rather than around the series in general.
Treat the mating assembly as part of the order and its length as a decision. Every model in this series uses a connector, so a mating assembly is required rather than optional, and it is offered in several cable lengths. Choose the length deliberately: the cable is part of the measuring circuit, and substituting a different one later is not a neutral act. Order it with the load cell, and tell us if you need something other than the standard lengths.
Then decide what reads it. An amplifier signal conditioner module provides a voltage or current output for a controller or logger, while a digital display adds a local reading with alarm setpoints, analog output and logging. Cal-Teds plug and play is worth specifying where sensors are exchanged between installations and you would rather not have calibration data transcribed by hand.
Describe the environment, the forces and how the sensor will be mounted, and we will help you settle on a model and the accessories it needs to arrive complete. Every capacity listed above is a stock item, and we discount for teaching institutions and research programmes.
HSW Series Load Cell Applications.
The Transducer Techniques HSW Series load cells serve demanding measurement requirements across multiple sectors, finding use where precise force measurement and resistance to environmental challenges are essential.
- Aerospace and Aircraft Testing: HSW Series load cells are used for structural assessment of aircraft components, ensuring they can withstand the conditions experienced during flight.
- Automotive Testing: The automotive industry uses these load cells for quality control evaluation of suspension systems, chassis, and brake system components.
- Industrial Automation: HSW Series load cells monitor forces in manufacturing and assembly processes, particularly where chemical exposure occurs.
- Food and Beverage Processing: These load cells measure and regulate forces in conveyor systems, mixers, and filling equipment exposed to regular washdown.
- Chemical and Pharmaceutical Manufacturing: HSW Series load cells assure quality and consistency in chemical-resistant environments.
- Materials Testing: These load cells are used for tensile, compressive, and fatigue evaluation in laboratory settings.
- Marine and Offshore Applications: HSW Series load cells provide force measurement on vessels and drilling infrastructure exposed to saltwater.
- Research and Development: Engineers use these load cells to evaluate component and system performance under harsh conditions.
- Custom Machinery and Equipment: HSW Series load cells are integrated into specialized testing and manufacturing systems.
- Energy and Power Generation: These load cells monitor force and load on wind turbines and hydroelectric equipment.
The Transducer Techniques HSW Series load cells' hermetic sealing and robust construction make them valuable tools for force measurement in demanding industrial applications where resistance to environmental factors is crucial. Their reliability and precision contribute to improved product quality, safety, and process efficiency.
Frequently Asked Questions
What does hermetically sealed mean on the HSW Series?
It means the gauge cavity is closed by a welded seal rather than by potting, gaskets or O-rings, and — critically — that the electrical exit is sealed as part of the same structure. The HSW uses a stainless steel moulded connector system designed to resist washdown and most chemicals, which is what makes the claim meaningful. A watertight body with a cable passing through a gland is a sealed load cell, not a hermetic one, and the difference shows up over years rather than weeks.
What capacities does the HSW Series cover and what do they cost?
Nine models: 500, 1,000, 2,000 and 3,000 lb at $795; 5,000 and 10,000 lb at $920; 20,000 lb at $1,050; 30,000 lb at $1,175; and 50,000 lb at $1,300. Compression calibration is included on every model with tension available as an option. Note that the four smallest capacities share a price, so if your requirement sits near the bottom of the range there is nothing to be saved by specifying tighter than you need.
How does the HSW compare with your environmentally sealed load cells?
The measuring performance is the same — identical accuracy figures, the same 2 mV/V output, the same capacity ladder above 500 lb. Three things differ. The HSW is hermetically sealed rather than environmentally sealed. Every capacity is 17-4 PH stainless steel, where our environmentally sealed equivalent uses aluminum at the lower capacities. And every HSW has a connector rather than an integral cable. You are not buying a better measurement; you are buying one that stays good in conditions that would slowly degrade the alternative.
How accurate is the HSW Series?
Nonlinearity and hysteresis are each 0.1% of rated output, nonrepeatability 0.05%, and zero balance 1.0%. Those are strong figures, and considerably tighter than our thru-hole and tension-link series at comparable capacities — which is worth knowing, because hermetic products are often assumed to trade accuracy for robustness. This one does not.
What is the natural frequency, and does it vary by model?
It does, and it is published for every model: 2,100 Hz at 500 lb, 3,500 Hz at 1,000 lb, 5,000 Hz through the 2K, 3K and 5K, 6,500 Hz at 10,000 and 20,000 lb, 8,000 Hz at 30,000 lb and 9,500 Hz at 50,000 lb. The trend runs opposite to intuition because a higher-capacity body is a much stiffer structure. If you are capturing impacts or rapid transitions rather than steady loads, the usable frequency content is a fraction of the ringing figure rather than all of it — so compare the two before choosing a capacity.
Is the HSW suitable for washdown environments and food processing?
That is one of the applications it is built for. The connector system is specifically designed to resist washdown and most chemicals, and 17-4 PH stainless steel handles the cleaning agents used in food and beverage production. What we would still want to know before you order is what is actually being sprayed, at what temperature and pressure, and how often — because “washdown” covers everything from a periodic rinse to daily high-pressure sanitation, and those are not the same duty.
Can the HSW be used in marine or offshore installations?
Marine and offshore work is a listed application, and hermetic construction in 17-4 PH stainless is the right starting point for salt exposure — salt-laden air is conductive and attacks unsealed sensors steadily rather than dramatically. Two things are worth raising with us rather than assuming: continuous immersion, which is a different requirement from splash and spray, and depth if anything is submerged. Tell us the installation and we will be straight about what the standard product covers.
What are the HSW's thread sizes, dimensions and weights?
Both change with capacity. Thread runs 3/8-24 UNF tapped 0.400" deep on the 500 lb through 2,000 lb models, 1/2-20 UNF at 0.500" on the 3,000 lb, 3/4-16 UNF at 0.750" on the 5,000 and 10,000 lb, 1-14 UNS at 1.000" on the 20,000 lb, 1 1/4-12 UNF at 1.250" on the 30,000 lb, and 1 1/2-12 UNF at 1.500" on the 50,000 lb. Height goes from 2.50" to 6.25", square width from 1.425" to 2.900", and weight from 1.9 lb to 12 lb. Take every figure from the row for the model you are ordering.
Which mating assembly do I need, and is it optional?
It is required, not optional — every HSW has a connector rather than an attached cable, so without a mating assembly there is nothing to wire to. Four stainless mating assemblies are offered by cable length: 6 ft at $81, 12 ft at $93, 20 ft at $111 and 50 ft at $265. Order one with each load cell. If none of the standard lengths suits your installation, or you want the far end terminated for a particular instrument, tell us at the time of order.
Does the HSW measure tension as well as compression?
The element responds to both. Compression calibration is included as standard, and tension calibration is an option priced at $125 for the lower capacities and $250 at the top of the range. The hardware does not change — what you are buying is a certificate covering the direction you will actually load it in. Specify it at the point of order, because a reading taken in a direction the certificate does not describe is not one you can defend.
Questions From The Field
My readings have started drifting slowly. Could moisture be the cause?
It is one of the likelier explanations, and the pattern you describe is characteristic. Moisture inside a gauge cavity creates a conductive path across the bridge, and the bridge reports that as an imbalance indistinguishable from load — so the symptom is a zero that wanders and repeatability that quietly deteriorates, rather than anything that looks like a fault. If re-zeroing keeps fixing it for a while and then stops, treat that as evidence rather than reassurance. Check the cable and the connector for damage first, since those are the usual entry points, and then talk to us about testing the cell.
Can moisture get inside a load cell that has never been exposed to water?
Yes, and it is the failure route people find hardest to believe. A cell that is sealed but not hermetic effectively breathes: the air in the cavity expands as the equipment warms and contracts as it cools, drawing ambient air in on each cycle. Moisture in that air condenses inside as the temperature falls. Published failure guidance lists internal condensation from temperature cycling alongside washdown and cable damage as a cause of moisture damage. A machine that runs warm through the day and sits cold overnight in a humid building supplies the conditions without any water ever touching the sensor.
How can I check whether a load cell has taken on moisture?
Insulation resistance is the standard test — measured with a meter capable of reading very high resistance, between the bridge circuit and the load cell body, with the sensor disconnected from any instrument. A healthy cell reads extremely high; moisture inside brings that figure down long before anything else looks wrong, which is what makes it a genuinely predictive check rather than a post-mortem. Expected values vary by construction, so contact us for the figure applicable to your model rather than working from a general number, and record the reading when the sensor is new so you have a baseline to compare against.
Is the connector really the weak point?
On hermetic products generally, yes — published guidance identifies the area where the external connection meets the sensor as the most common place a hermetic seal fails, because the electrical path has to cross the sealed wall somewhere. That is precisely why this series uses a stainless steel moulded connector system rather than a cable gland. In service, the practical implications are ordinary: keep the connector mated or capped, do not leave it open in a washdown area, support the cable so its weight and movement are not carried by the connector body, and inspect the seal face when you disconnect for recalibration.
Can welding near the load cell damage it?
It can, and this catches people out because the damage is electrical rather than mechanical. Welding currents and lightning both put transients through anything they can find a path along, and a strain gauge bridge is a low-resistance circuit connected to a metal structure. Disconnect the load cell and its cable before welding on or near the assembly it is mounted in, and never let welding return current find its way through the sensor. If the sensor was connected during welding nearby, check the zero against the certificate before trusting anything it reports.
Does hermetic sealing mean I can pressure-wash it directly?
The construction is designed to resist washdown, which is a great deal more than most load cells will tolerate, but it is worth distinguishing the sensor from the installation. High-pressure jets directed at a connector seal face, at a cable entry or at the joint between the sensor and its mounting are a harder test than incidental spray, and the cable and its routing are usually the more vulnerable part of the assembly. Describe your cleaning regime to us — pressure, temperature, chemistry and frequency — and we will tell you honestly whether it sits inside what the product is built for.
How much longer will a hermetic cell last than a sealed one?
There is no honest single number, because it depends entirely on what the sensor is exposed to — in a clean, temperature-stable laboratory the two may be indistinguishable for a decade. The difference is one of mechanism rather than duration. Potted, foam and adhesive protection degrades with time and exposure, so a sealed cell's protection is at its best on the day it is installed and declines from there. A welded seal does not degrade on that schedule. The right way to weigh it is to ask how bad it would be to discover, in year six, that the readings had been drifting for a year.
Do I still need to protect the cable if the load cell is hermetically sealed?
Yes — and this is where a good specification is most often undone. Cable damage is one of the leading routes for moisture to reach a sensor, and a cut, crushed, chafed or rodent-damaged cable will wick water toward the connector regardless of how well the body is sealed. Route it so it is not walked on, driven over or pulled at the connector; support its weight; avoid tight bends at the exit; and where it runs through an aggressive area, protect it mechanically. A hermetic load cell on an unprotected cable is a well-built front door with a window left open.