S. Himmelstein and Company (Hoffman Estates, IL) has been designing and manufacturing torque measurement transducers and instrumentation since 1960. The company’s products offer significant advantages that enhance their overall performance under real-world conditions – not just in the calibration stand. To find out more about S. Himmelstein’s unique torque measurement products, Tech Briefs recently spoke with Steve Tveter, Vice President of S. Himmelstein.
Tech Briefs: Tell us about your company and your place in the market.
Steve Tveter: We’re a relatively small, privately held company strictly focused on manufacturing devices for precise, accurate measurement of torque. The company was launched based on the invention of the signal transfer technique to transfer electrical signals from a rotating shaft without having to make physical contact with the rotating shaft. The invention of that technology launched us into the torque measurement business since that is an ideal application for the technology. It’s somewhat of a niche product and industry. We’ve sold to virtually every manufacturing company you can think of all over the world. It’s a product that’s important to manufacturers because it’s critical to establish their product performance, determine the efficiency of their products, and optimize their products.
Tech Briefs: What are the major market factors driving the demand for torque measurement with ever increasing accuracy/performance?
Tveter: There are a few different factors. Obviously, manufacturers are trying to be as cost-effective as possible in the development of their products. Electric motors are a big part of our business; specifically, manufacturers of electric motors. The government – the Department of Energy – has mandated efficiency standards now for electric motors. So, it’s become more important for those manufacturers to make accurate measurements.
Electric motor efficiency is calculated by looking at the amount of electrical power input into the motor, and then the output of the motor is mechanical power output – torque and speed – that’s measured with one of our devices. They take the electrical input and the ratio between the power out and the electrical input and determine the efficiency.
Obviously, the more efficient the motor, the less it will cost to run that motor. To be able to make that efficiency measurement, you need to measure the mechanical power output transmission with one of our devices, and the more accurate our device can be, the more accurately our device can do that and the more accurate representation they have to make a measurement of motor efficiency.
Tech Briefs: How is the user assured that the torque transducer is performing according to its published specifications?
Tveter: If somebody’s using our device to establish the performance of their equipment, they want to have confidence in the credibility of the equipment they’re using to make that measurement. We calibrate every device before it leaves here. We have a rather extensive calibration laboratory that covers a broad range of measurement capabilities. Our laboratory is also accredited to ISO 17025 standards. The agency that accredits us is NVLAP, and they’re part of the National Institute of Standards and Technology (NIST).
NVLAP regularly audits our procedures and equipment to make sure we’re doing everything correctly. When you calibrate a torque transducer, the unit is installed into a test fixture. You apply a load by hanging weights at a distance from the center line of the shaft of the transducer. It’s critical to know exactly how much that weight is and what the length of the arm is. When the customer gets one of our transducers, they get a fully accredited calibration certificate stating what the performance of the transducer is and indicating it was calibrated with equipment that is all traceable to national standards.
Tech Briefs: What are some of the critical characteristics of a torque measurement device to ensure the ability to meet the accuracy requirements in a real world/practical test environment?
Tveter: What most customers look at and what most of our competitors specify is that the transducer is accurate to within .1% of its full-scale rating. The difficult part of that is, unless you understand how that specification was developed, you’re not comparing apples to apples if you’re looking at our specs versus our competitors’ specs.
Primary factors we look at in terms of accuracy is to give the customer a combined accuracy that includes the linearity and the hysteresis performance of the transducer. Things we think are critical that the customer doesn’t consider on the surface are that our transducers have considerable mechanical overload or safety factors. This protects the sensor from loading that is in excess of its rating.
The other characteristic we think is critical is the electrical output signal. We have the capability to have what we call overrange on the electrical output signal. The torque transducer or any kind of torque measurement is a more dynamic measurement – it’s not static like a load cell or measuring weight. Torque is a rotating measurement – everything is moving. Torque is not a level signal. You’ve got oscillations, and those oscillations are significant. If you don’t have enough overrange on the electrical output signal, the peaks or maximums of those sinusoids will be clipped off, impacting the average torque value being displayed.
Tech Briefs: What type of support do you provide to customers?
Tveter: Installing a torque transducer, since it’s installed in a dynamic drivetrain of the equipment being tested, is a little more of an engineering task to make sure it’s done correctly.
From the beginning, we typically consult with the customer about their application and then give them guidance of how to do the installation correctly and optimally so that, number one, it’s safe, because you have things spinning around and in some cases, these applications are going at pretty high RPM. And also, we make sure they are not going to potentially damage the transducer. We support them with ongoing periodic calibration of their transducers so that they can, on a regular basis, verify the performance of that transducer and make sure that it’s still giving them good results.
Visit S. Himmelstein at www.himmelstein.com.