Durometer Type AO PTC® Instruments Ergo Style #408AO

The following procedures are based on ISO 7619-1 Standard. This standard is recognized as being definitive for this model, however, not all applications require such stringent controls.

This durometer should be used when material readings are below 20 with Type A durometer.

The surface of the sample to be tested shall be clean and smooth. The sample should be at least 1/4" (6 mm) in thickness. Thinner materials can be stacked (maximum of 3 layer) to obtain the minimum thickness (DO NOT GLUE). Such results may not agree with those of a solid specimen. The sample should be large enough so that the indenter is at least 0.6" (15 mm) from any edge. The surface of the specimen shall be flat and parallel over a sufficient area to permit the presser foot to contact the specimen over an area having a radius of at least 0.35" (9 mm) from the indenter point. The temperature of the specimen should be 73.4°F ±3.5°F (23°C ±2°C). The specimen should be allowed to rest at this temperature for at least 1 hour prior to testing.

Place the specimen on a flat, hard, horizontal surface. Turn the Max Hold hand so that it is past 100 dial points and will not impede the indenter. Hold the durometer vertically with the tip of the indenter at least 0.6" from any edge. Apply the presser foot to the specimen as rapidly as possible, without shock, keeping the foot parallel to the surface of the specimen and ensuring the indenter is normal to the rubber surface. Apply just sufficient force to obtain firm contact between the presser foot and the specimen. Take the reading at the specified time after the presser foot is in firm contact with the specimen. The standard test time shall be 3 sec. for vulcanized rubber and 15 sec. for thermoplastic rubber. Make 5 tests at least 1/4" apart and report the results and their median value.

If using the Max-Hand for maximum readings, set the ancillary hand of the durometer near the pointer (below 5 points on the dial) before taking the reading.

For a complete calibration check of mainspring, and visual and mechanical check of indenter, the instrument should be returned to PTC® (see Guarantee & Calibration Service) or refer to ISO 7619-1 Standard. PTC® recommends the unit be returned at least every 12 months for this check. For a quick field check, follow the guidelines below. Under no circumstance should a test block be used as a standard to calibrate a durometer.

1. The pointer should read zero when no force is applied to the indenter of the durometer.

2. Hand hold the durometer and insert the indenter into the indentation in the brass button of the calibrated test block. Apply enough force to make firm contact between the top surface of the test block and the base of the durometer. The dial reading should agree with the value stamped on the check block (±1). Several tests should be made and the results averaged.

3. The indenter must protrude 2.5 ±0.02 mm below the base of the durometer.

4. When the indenter is fully displaced, the durometer should read 100 points. Use care as to not damage the tip of the indenter.