An article titled, "Measuring Tape Calibration" appeared in
The Equipment and Facilities Specifications Newsletter, in September 2011, (Editor: Ivars Ikstrums.) It included a study comparing the length of various steel and fiberglass measuring tapes. The study was similar to the one documented in the Measurement News #50, November 1991.
The complete newsletter is available at the USATF web site.
http://www.usatf.org/groups/of...ewsletter-201109.pdfI included the text from the article below.
The Equipment and Facilities Specifications Newsletter September, 2011 Volume 21-2 Measuring Tape Calibration A steel tape measure is frequently used to certify a record performance in the throws or jumps. However, according to the rule books, a steel tape, by itself, is not enough:
NCAA Rule 2-12 recommends that, for general use, steel tapes be certified for accuracy by an appropriate testing agency. Rule 6-1-15 requires that records are measured with a calibrated steel tape.
USATF Rules 262.5 and 264.2 require that records are measured with a certified steel tape.
IAAF Rule 260.26 requires that records are measured with a certified calibrated steel tape. Rule 148 requires all measurements in higher-level meets be made with a certified calibrated steel tape.
This article concerns the necessity of calibrating steel tapes. It does not discuss Electronic Distance Measurement (EDM).
During the summer, the editor had the opportunity to compare several steel tapes in a controlled environment. This initially started out as a simple science project to determine variability between steel tapes. However, since this project required a measure of effort and logistics, it was decided to expand the scope of testing and include fiberglass tapes, as well. In the end, 7 steel tapes and 56 fiberglass tapes were tested. The tapes ranged the full gamut of new, almost new, used and visibly used conditions.
Background: Permission was secured from a large local shopping mall to use one of their passageways during the middle of the night. A 96 meter continuous stretch was found that was clean and freshly waxed. A 100 meter stretch would have been ideal, but this was good enough, considering the willingness of the mall’s operations manager to allow us access without any charge or bureaucratic wrangling.
Several steel tapes were gathered from the Pacific Northwest Track & Field Officials Assn, PNTF Youth Committee, Seattle Masters Athletics Club and the editor’s garage. When the project was expanded, a large collection of fiberglass tapes were secured from the above groups and a local high school.
Checking these tapes against a certified "gold standard" steel tape would have been the preferred method, but such a tape was not available. Instead, a Leica Disto A5 laser distance finder was used. Under the conditions of use, the manufacturer states the unit’s error is approximately ±2 mm.
Virtually all steel tapes must be pulled with a tension of 50 N (about 11 lb) to measure accurately. To ensure consistency during this test, an Ametek-Chatillon digital force gauge was used to achieve the 50 N tension for every tape. The fiberglass tapes were pulled with 20 N tension (about 5 lb), as several of these tapes had "20 N" written on them.
Setup: A flat metal plate, 12"x 12", painted in flat white, was set up at one end of the passageway. A square was used to ensure its perpendicularity to the floor. This was used as the target for the laser, and the zero point of the tapes. A steel rule was placed on the ground at the other end of the passageway. The position of the laser was adjusted until the desired distance to the white plate was achieved (resolution of the Disto is 1 mm or 1/32"). The rule was taped to the ground at that point. This process was repeated for each length of tape that was to be tested.
Test: The zero point of each tape was determined and affixed, relative to the white plate. The force gauge was clamped to the tape at the other end and slowly pulled. At the point where the required tension was achieved (50 or 20 N), the tape’s length relative to the affixed steel rule was noted. Over the course of five hours, this process was repeated over and over. Given the time constraints, and only two people to perform this task, only the lengths of the tapes were checked; intermediate points were ignored.
Note 1: The above values are temperature compensated. Most steel tape fabrication is referenced to 68 °F. The air temperature just above the floor in the mall was 73 °F and did not vary by more than 0.5 °F over the evening, as measured by a Fluke 971 meter. This expansion was removed from the measured error.
Note 2: The Error value above is the amount which the tape is longer (+) or shorter (-) than the laser reference distance (temperature compensated). For example, the US Tape 59944 was tested at its full length of 90 m. Its 90 m mark was actually 0.6 cm (6 mm) beyond the laser reference distance, meaning that, at full length, it produces a reading that is 0.6 cm less than the true distance.
The above data are not definitive. The error contribution of the laser is not completely known. Also, tapes are usually calibrated on long steel tables -- the difference in friction between such a table and the waxed floor at the mall is not known.
The fiberglass tapes displayed greater variability. Samples from Cen-Tech, Champion, Empire, Fina, Kobalt, Komelon, Martin, M-F Athletic, Springco, TAG and VS Athletics were represented, as well as several no-name tapes from Taiwan and China.
The best overall performance was from the Springco tapes, many of them matching the steel tape performance. The Komelon 100 ft and 330 ft tapes matched the Springco tapes, but curiously the Komelon 200 ft tapes consistently showed a small amount of error. Other brands stretched as much as 7 cm over the 96 m length.
The takeaways from this project are:
1. The measurements performed were not at a certification level. Nevertheless, some interesting trends were seen, particularly with the fiberglass tapes.
2. Some fiberglass tapes stretched considerably. Some of this may be due to how they were made, and some older tapes may have stretched due to use. Checking all fiberglass tapes in your inventories against some kind of standard is highly advisable. tapes in your inventories against some kind of standard is highly advisable.
3. To be fully compliant with the rule books, any steel tape, which is used for documenting record performances, must be certified. How can this be done?
Lufkin offers several 100 ft certified tapes, and one of its 200 ft Peerless tapes certified as model C1278CAL. Purchase is by special order thru a distributor.
Channel Supplies calibrates and sells a variety of tapes up to 100 ft in length. They will also calibrate a customer’s tape at $65 per side, assuming the tape will fit up to their test fixture. Contact them at 830-792-5538 before sending anything. Starrett 100 ft and 30 m certified steel tapes are available from www.mcmaster.com on page 2236.
US Tape also certifies tapes up to 100 ft in length. They charge $65 for setup and $2.50 for each specified point.
Note: Many certified tapes have a certificate for the full length of the tape only. If certification of intermediate points
is required, then this will be a custom calibration.
The National Institute of Standards & Technology (NIST) will certify tapes to 200 ft for $499, including 7 points. 300 ft or 100 m tapes are $100 extra, and additional points on the tape are an extra $10 each.
4. If possible, associations (or individuals) should consider acquiring some type of "gold standard" for use in checking fiberglass tapes. There are a few of options for doing so:
a. Obtain a certified 100 ft tape as noted above. The cost is not prohibitive. It can be used directly to check FG tapes to 100 ft. It can also be used to lay out 200 or 300 ft lengths for longer measurements (while this is not a valid calibration method, it should suffice for checking FG tapes).
b. Use an uncertified, off-the-shelf steel tape. However, this should first be checked, side-by-side, with two or three other steel tapes to ensure yours is not inexplicably in error. Look for agreement within 1 cm.
c. Obtain a laser measurement tool, such as a Leica Disto or Fluke 421D, and use that to lay out any distance up to 100 m for tape comparison. Avoid areas with temperature extremes or direct sunlight, as those degrade the accuracy of the laser devices.
# # #
