Tuesday, August 5, 2008

A Friendly Tech Tip: Size Matters

How relevant is the capacity of a force or torque measuring instrument to the expected load during a test? More than many people think.

The accuracy of measuring instruments can be specified in two ways. In some cases, accuracy is specified as a percentage of actual reading, in other cases as a percentage of full scale. Mark-10 specifies accuracy as a percentage of full scale. What does that mean exactly?

Consider the following analogy: Suppose you are weighing yourself on a 300 lb capacity common bathroom scale that specifies accuracy of ±2% of full scale. 2% of 300 lb equals 6 lb. If you weigh yourself and the scale shows 150 lb, your true weight could be anywhere between 144 and 156 lb. Even though the accuracy specification is ±2% of full scale, the percentage reading error could be up to 6 lb / 150 lb = 4%. Suppose your weight is only 100 lb. The percentage reading error could be as high as 6%. The lower the load, the greater the percentage reading error.

The same principle applies to our force and torque measuring instruments. Since accuracy is typically specified as a percentage of full scale, there is a fixed numerical value by which the reading may be incorrect at any point in the range of the instrument. Accordingly, it's important to select an instrument with capacity as close as possible to the expected maximum force.

For example, our Series BG digital force gauges specify accuracy of ±0.2% of full scale ±1 digit (increment). In the case of the
BG100 force gauge (with capacity of 100 lb), the specification translates into an error of 0.25 lb. This is calculated as follows: 100 lb x 0.2% = 0.2 lb + 1 digit [0.05 lb] = 0.25 lb.

If the total observed force is 80 lb, a maximum error of 0.25 lb represents a percentage reading error of approximately 0.3%. If, however, the total observed force is only 2 lb, the percentage reading error is 12.5%. Such an error could easily mean the difference between an acceptable product and a reject.

A quick evaluation of the maximum expected load during your test and an evaluation of the available capacities of force and torque measuring instruments will go a long way in ensuring that your samples are tested as accurately as possible.

Questions? Comments? Feel free to post!

Friday, July 25, 2008

"Hi, I'm Looking For A Pull Tester"

Over the years we've come across numerous inquiries for such items as "wire pull testers", "peel testers", "tensile testers", and other similarly worded "testers". Some customers are surprised to hear that we don't sell testers per se, but rather, that a Mark-10 tester is actually a system consisting of several individual components.

The number of possible combinations of components to satisfy a requirement can be quite extensive. This broad range of combinations makes it possible to customize a tester suited to the exact requirements of the test, as opposed to an integrated tester available in only one flavor.

Tester components typically include a test stand, force gauge, grips, software, and accessories. To some customers, these individual product terms may not be familiar. To help understand what these components are and how they can be configured for specific applications, we've developed a section of our website (click here) that identifies and explains system components. In addition, comparison charts are available to identify the major differences between our various series of gauges and test stands.

If our website still isn't clear enough, further assistance in configuring a tester is always a quick phone call or email away.

Happy testing!

Thursday, July 10, 2008

Test Stand Travel / Clearance / Throat: What's The Difference?

With so many different force test stands available, choosing one that suits your needs may seem a difficult task. However, this decision can be made easier by clarifying some confusion in the differences between specifications for travel distance, clearance, and throat depth.

Clearance (also known as daylight) is defined as the maximum possible distance between the force gauge's loading shaft and the base of the test stand. This specification is useful in determining if the sample's dimensions fit into the constraints of the test stand. Clearance does not take grips, fixtures, or other attachments into account. That is, if such accessories are used to help secure the sample during a test, these will cut into clearance, since one such accessory is normally mounted to the force gauge, and the other to the test stand's base. It is, therefore, important to note the overall length of these accessories and factor them into your calculations. If it is determined that the clearance is insufficient, most Mark-10 test stands' columns can be extended.

Throat depth is also a distance specification, only this refers to the maximum possible distance between the centerline of the force gauge's loading shaft and the column. In determining whether a sample will fit within the constraints of the stand, throat depth should be doubled to calculate the maximum possible sample diameter.

Travel distance (also known as stroke) is often confused with clearance, but the two are quite different. Travel distance is defined as the maximum travel the force gauge is able to move vertically along the length of the column. Many applications require relatively little travel, such as Belleville washer testing. However, in testing elastic materials such as rubber, plastics, elastomers, and others, longer travel is required.

With these specifications clearly defined, choosing an appropriate test stand should not be too daunting a task after all. We provide a comparison chart that compares stands on these, and other, specifications, and can be seen here: http://www.mark-10.com/instruments/stands/stand%20comparison.html.

Happy testing!

Monday, June 23, 2008

Oil Prices... High Enough?

So, how about those oil prices? Isn't that what everybody is talking about? I think they aren't high enough. Want to know why? I haven't seen any significant push for our representatives in Washington to make any meaningful effort in alternative energy development. Perhaps $8 or $9 per gallon, as our European friends are currently paying, would finally push us to act. How about $15? $20? Do I hear $30? Surely, with our technological prowess, we are able to develop a suitable battery for electric cars. We do hear about technological breakthoughs here and there, but not at the scale I would expect from a frustrated America. Last time we were truly frustrated, we put a man on the moon. Have we lost the will? What do you think?


Welcome to MeasuringUP - The Mark-10 Blog! We've launched this blog to share our thoughts on the force and torque measurement market and how it affects our customers, casual observers, and anyone else with an interest in the industry. We'll be discussing relevant topics such as testing applications, testing techniques, technical tidbits, product spotlights, industry news, and more.

We hope that our posts will help spur constructive dialogue in all these areas, creating an interactive forum that you will visit again and again. Of course, in order for this blog to reach its potential as a source of education as well as entertainment, we'll need your feedback! Please post your comments often - we all look forward to reading them.