RadioShack 22-168
The RadioShack 22-168 is a 2000 counts handheld digital multimeter with RS-232 connectivity.
Hardware
- 3 1/2 digit ADC with bandgap reference: Maxim MAX130CPL (datasheet) (marking: "Maxim MAX130CPL 0138-3 C10039")
- CPU: Metex KS57C2016 (Samsung KS57C2016 4-bit microcontroller with custom Metex firmware) (marking: "Metex 93D3 KS57C2016-02 410")
- ?: Metex 9005 (marking has ST logo: "Metex 9005 MET7ACS 92A32792BA")
- Crystal: 4.1856MHz crystal
- 555 timer: Intersil ICM7555CBA (datasheet) (marking: "H 7555 CBA L405")
- Quad analog switch/quad multiplexer: Motorola 14066B (datasheet) (marking: "14066B XAC334")
- Quad 2-input NAND gate: GD4011BD
- Optoisolator: Lite-ON LTV-817
- Unidentified ICs: Two ICs, which appear to be SSOP8 packages are hidden behind black goo. The purpose of the goo is unknown.
Photos
Device, angle
Mugshot
Device, back
"Metex" logo on the stand
Battery compartment
Battery cover
Opened up
Spare fuse
Front cover, PCB still mounted
Front cover
Rear cover
Bare electronics
Range-switch sandwiched between PCBs
Range-switch
Main PCB, front
Secondary PCB, front
Main PCB, front, illuminated
Main PCB, back, illuminated
Secondary PCB, front, illuminated
Secondary PCB, back, illuminated
Unidentified components protected by black coating
Metex KS57C2016 CPU
4.1856 MHz crystal
MAX130CPL ADC
Metex 9005 7ACS (ST Micro logo)
MC14066B Quad Analog Switch/Quad Multiplexer (left) and GD4011BD quad 2-input NAND gate (right)
555 Timer
RS-232 optoisolation
LCD display
LCD display, back
TODO
Protocol
TODO