美国NIST标准品 SRM 6002a Multi-Junction Thermal Converter-600 ohms 多结的热转换器- 600欧姆 each SRM 6002b Multi-Junction Thermal Converter-1040 ohms 多结的热转换器- 1040欧姆 each SRM 6003b Portable Vacuum Standard 1 Pa to 700kPa (Commercial Mercury Manometer Replacement) each SRM 6003a Portable Vacuum Standard each