Static dissipative materials suppress sparks, which prevent ignitions of flammable solvents and ESD damage to electronic devices. Static dissipative materials are often selected by requiring that their resistivities not exceed specified values. For standardization and consistency, these important resistivity measurements are governed by several standards. Furthermore, the alternating polarity method significantly improves measurement repeatability. Resistivity is well defined when the current from a DC applied voltage is constant. However, for many static dissipative materials, the measured current decreases with time in milliseconds to tens of seconds. Analysis presented here shows that contact resistance between the measurement electrodes and the material under test can cause the measured current to decrease with time. The contact resistance is modelled as a thin, barrier layer between the measurement electrodes and the material. Analysis of an equivalent circuit for surface resistivity measurements finds that the initial measured current is determined by the material resistivity. The measured current then decreases exponentially with time towards steady state in materials having ohmic resistivity. The time constant is determined by the capacitance of the barrier layer and the material resistance. The DC steady state resistance measures primarily the resistance of the barrier layer that is often many times larger than the resistance of the material. Consequently, the steady state resistance may significantly underestimate the performance of static dissipative materials.

静电耗散材料可抑制火花，从而防止易燃溶剂着火和对电子设备造成 ESD 损坏。静电耗散材料的选择通常要求其电阻率不超过规定值。为了标准化和一致性，这些重要的电阻率测量受多个标准的约束。此外，交替极性方法显着提高了测量的可重复性。当来自直流施加电压的电流恒定时，电阻率是明确定义的。然而，对于许多静电耗散材料，测得的电流会随着时间的推移而减少，以毫秒到几十秒为单位。此处提供的分析表明，测量电极和被测材料之间的接触电阻会导致测量电流随时间减小。接触电阻被建模为测量电极和材料之间的薄阻挡层。对表面电阻率测量等效电路的分析发现，初始测量电流由材料电阻率决定。然后，在具有欧姆电阻率的材料中，测得的电流随着时间向稳态呈指数下降。时间常数由阻挡层的电容和材料电阻决定。直流稳态电阻主要测量阻挡层的电阻，通常比材料的电阻大很多倍。因此，稳态电阻可能会大大低估静电耗散材料的性能。对表面电阻率测量等效电路的分析发现，初始测量电流由材料电阻率决定。然后，在具有欧姆电阻率的材料中，测得的电流随着时间向稳态呈指数下降。时间常数由阻挡层的电容和材料电阻决定。直流稳态电阻主要测量阻挡层的电阻，通常比材料的电阻大很多倍。因此，稳态电阻可能会大大低估静电耗散材料的性能。对表面电阻率测量等效电路的分析发现，初始测量电流由材料电阻率决定。然后，在具有欧姆电阻率的材料中，测得的电流随着时间向稳态呈指数下降。时间常数由阻挡层的电容和材料电阻决定。直流稳态电阻主要测量阻挡层的电阻，通常比材料的电阻大很多倍。因此，稳态电阻可能会大大低估静电耗散材料的性能。然后，在具有欧姆电阻率的材料中，测得的电流随着时间向稳态呈指数下降。时间常数由阻挡层的电容和材料电阻决定。直流稳态电阻主要测量阻挡层的电阻，通常比材料的电阻大很多倍。因此，稳态电阻可能会大大低估静电耗散材料的性能。然后，在具有欧姆电阻率的材料中，测得的电流随着时间向稳态呈指数下降。时间常数由阻挡层的电容和材料电阻决定。直流稳态电阻主要测量阻挡层的电阻，通常比材料的电阻大很多倍。因此，稳态电阻可能会大大低估静电耗散材料的性能。