AATCC 76-2000 Electrical Surface Resistivity of Fabrics.
6. Test Specimens
6.1 Adjust the size of fabric test speci- mens to suit the electrodes of the particular equipment being used. When using parallel plate electrodes, the width of the specimen must not exceed the width of the electrodes. When using the concentric rings, any size specimen at least as large as the outer ring may be used. Avoid con- taminating the area on which the measurement is to be made.
6.2 Specimens for use with instruments providing parallel plate electrodes. Prepare 2 sets of 3 test specimens each, 1 set each so that the direction of testing is parallel to the yarns in the length direction of the fabric and 1 set with the direction of testing parallel to the width direction of the fabric.
6.2.1 Test specimens for use with instruments providing concentric ring elec- trodes. Prepare 1 set (3 test specimens) since, with this type instrument, the resistance is measured in both fabric length and fabric width directions simultaneously.
6.2.2 Depending on the fabric con- struction or end-use, it may be advisable to differentiate between face and back measurements. Each test specimen should be taken from a different part of the fabric.
7.1 Calibrate the electrical resistance meter according to the manufacturer’s recommendations. This calibration should be repeated periodically (see 10.3).
7.2 Condition the test specimens in a suitable testing chamber or conditioning room at a predetermined relative humidity that will reflect the conditions at which information on the electrical resis- tivity of the fabric is needed.
7.2.1 For most fabrics which require antistatic treatments or whose static propensity is critical, measurements at 20% relative humidity will be most meaningful.
7.2.2 In less critical situations 40% relative humidity may be employed.
7.2.3 For special requirements other relative humidities may be used. For example, preconditioning at 50% ± 2% RH at 21 ± 2°C is required for antistatic sheeting, film and textiles for use in hos- pital operating rooms (see 11.2.1). Measurements may be made under other conditions or ranges of conditions that are applicable to the end use (such as 65% RH and 24°C). It is preferable to keep the temperature or humidity consistent for all measurements.
7.2.4 If it is necessary to measure electrical resistivity under a broad range of conditions, additional tests may be run at 65% RH and at 24°C or other settings ap- plicable to the end use. It is preferable to keep the temperature or humidity consistent for all measurements.
7.3 Optionally remove static charges on the surface of the fabric by passing a radioactive bar over both sides of the fab- ric (see 11.4).
7.4 Place a test specimen in firm contact with the electrodes. The contact with the electrodes should be such that, when additional pressure is applied between the fabric and the electrodes, the test results are not affected.AATCC 76 pdf download.