Review and teardown of 3 types of Precision Voltage Reference Modules which are useful for checking the calibration of Digital Multimeters.
Teardown of a Keithley 178 Digital Multimeter manufactured in 1979. This multimeter was one of a number at that time which used the Intersil ICL7103A and ICL8052A chip set which simplified multimeter design and manufacture.
The Keithley 168 autoranging digital multimeter. Manufactured in the early 1970’s. Used the 74360N multimeter chip which is now obsolete. D.C. voltage range from 0.1mV to 1000V. A.C. voltage from 0.1mV to 500V. Current ranges from 0.0001mA to 1A. Ohms from 0.1 ohm to 20 mega ohm. Input resistance is 10 mega ohm.
Review and teardown of the Thurlby 1905A Intelligent Digital Multimeter was designed and manufactured in the 1980’s by Thurlby Electronics Ltd. The meter is a 5½ digital manual ranging multimeter with keyboard programmable computing and data logging facilities. The basic accuracy is ±0.015% on the D.C. ranges.