The low-noise and extremely precise SIM921 AC Resistance Bridge provides millikelvin accuracy for cryogenic thermometry applications. With excitation power below 100 aW, measurements at temperatures below 50 mK with negligible self-heating errors are possible. Utilizing the four-wire circuit for measurement eliminates the direct effect of lead resistance on the result.低噪声和精确sim921交流电电桥提供低温测温精度应用millikelvin。着激发功率低于100 AW在温度低于50 mK的可以忽略不的热差的测是可的。利用四线电消了引线电对测结果有直接影响。