摘要:

A method of measuring the moment of small magnetic dipoles is described. The dipole to be measured is rotated inside of a fixed coil, and the voltage induced in the coil is measured by means of an alternating‐current amplifier. The limiting sensitivity is computed from the calculated signal‐voltage and the thermal agitation in the input circuit. In the practical application the theoretical sensitivity is approximately obtained and moments of 3×10−7c.g.s. unit can be detected and with a specimen 1.5 cm on a side 8×10−8c.g.s. unit/cc can be detected. The method has been applied to the measurement of the polarization in sedimentary deposits.

ISSN:0034-6748    

DOI:10.1063/1.1752549

出版商:AIP    

年代:1938

数据来源: AIP

摘要:

Experiments employing a new type of regenerative direct‐current amplifier have shown that such equipment is unsuited for use, except, perhaps, in the laboratory. A successful system of amplification employing vacuum tube amplifiers and commutators for inverting and synchronously rectifying the resulting amplified alternating potentials is described. Thermocouple electromotive forces less than 10−9volt are readily indicated on a portable microammeter. The over‐all useful amplification with portable equipment exceeds 50,000.

ISSN:0034-6748    

DOI:10.1063/1.1752550

出版商:AIP    

年代:1938

数据来源: AIP

摘要:

This general purpose, balanced triode voltmeter is stabilized by adjusting shunt resistors until the effective values of &mgr; andIpare the same for both tubes. Built‐in testing equipment is provided. The electrical zero of the galvanometer is unaffected by changes of ±20 percent in power‐supply voltage when the circuit has a d.c. sensitivity of 40,000 mm/volt. The tubes need not be specially selected. The balancing principle may be adapted for use in any circuit requiring matched tubes.

ISSN:0034-6748    

DOI:10.1063/1.1752551

出版商:AIP    

年代:1938

数据来源: AIP

ISSN:0034-6748    

DOI:10.1063/1.1752552

出版商:AIP    

年代:1938

数据来源: AIP

ISSN:0034-6748    

DOI:10.1063/1.1752553

出版商:AIP    

年代:1938

数据来源: AIP

ISSN:0034-6748    

DOI:10.1063/1.1752554

出版商:AIP    

年代:1938

数据来源: AIP

ISSN:0034-6748    

DOI:10.1063/1.1752556

出版商:AIP    

年代:1938

数据来源: AIP

ISSN:0034-6748    

DOI:10.1063/1.1752557

出版商:AIP    

年代:1938

数据来源: AIP