The routine administrative aspects of an ergonomics consulting business are pretty mundane – renew software licenses and insurance plans, make sure everyone gets their annual training, pay the bills, send the invoices….not the stuff of dreams when I launched this business 30 years ago. Maintaining our equipment isn’t exciting, but it has to be done.
Force gauges and dynamometers are our most specialised hardware – each of our ergonomists has a force gauge that measures pushing and pulling forces, a grip dynamometer that measures grip strength or effort, and a pinch dynamometer that measures pinch strength or effort. The image above right shows a pinch dynamometer being used to “force-match” the effort required to pull tape from a box.
Why do we need force gauges and dynamometers?
Without these gauges, an ergonomist can only measure weight (if a scale is available), and can only assess pushing and pulling based on employee estimates. One of the most common of these estimation methods is called the “Borg CR 10” scale. Participants are asked to rate their effort on a scale, with 10 meaning “maximal” and 0 meaning “no effort.” Of course, what’s near-maximal for me might be negligible for you, so the common criticism is that results depend on whom you ask. Our clients expect objective measures, so we measure job demands with hardware and consistent procedures.
Eventually, we’ll be able to use gloves with sensors in them to measure the forces applied by the worker’s hands. This will be amazing, because such technology would also capture the exact direction of the force, and the task’s frequency and duration. At some point even further down the road, we believe that this tech will integrate with biomechanics software that will evaluate the risk of hand, wrist, elbow, shoulder, back and neck injury. Force-measuring gloves are available now, but they are not yet cost-effective, or practical for use in all work environments.
Annual gauge calibration, despite the drudgery of it, is important. Here’s why.
- Our gauges take a beating on a day-to-day basis. We store them in padded compartments of our sling bags, but even being pulled out and put back into the case can rub them the wrong way (pun intended).
- They’re used frequently, because we take at least 5 measurements for every push, pull, grip, or pinch that we study. (And often many more than 5!)
- Some of the forces that we need to measure are difficult to access or interface, so we often have to use creative ways to secure the gauge and the work piece, and this can put additional strain on the device.
- We work in all types of weather – indoors, outdoors, and in snow and rain. We also work in environments that require us to sanitize our equipment at the beginning and end of the day.
- If a gauge is not reading correctly, we would make an error our analysis – a high reading will overestimate risk, and a low reading will underestimate risk. A gauge that is acting erratically will waste the ergonomist’s time, causing us to obtain many readings when only a few would have sufficed.
- When a gauge gets dropped, we can’t use it until it has been re-calibrated. This usually means that we have to ship a calibrated gauge to the ergonomist. Obviously, we take measures to avoid dropping gauges, but it happens occasionally.
We can do calibration checks any time two of us are in a room together – If I push the end of my gauge against the end of yours and both gauges should read the same value. (Pulling works the same way.) But at least once per year, we send our gauges away to be professionally calibrated, and invariably a couple get retired every year. Our service puts stickers on our gauges to show that they’ve passed the test. (These often fall off….I ask the service every year to find better stickers for us.) In order to send the gauges away, we have to own enough gauges to allow one set to be out for calibration while the other set is in use.
If your organization owns force gauges and dynamometers for measuring push, pull, grip, and pinch forces, are you calibrating them annually?