Saturday, June 27, 2015

Teardown of Mastech MS8268 multimeter

The advertising for this multimeter stated that it has "warning when incorrect banana jacks are used relative to function switch setting".  I got curious about how the meter detected the banana plugs.  At first, I thought that there is an optical proximity sensors under each jacks, but that was an incorrect guess.  Each jack has a momentary switch at the bottom.  The switch has an plastic plunger, which insulates the detection switch from the banana contacts.

Light pipes for ring indicators around banana jacks visible.
One of the light pipes, which forms the ring around a banana jack, is removed and shown separately on the right.
Red and black plastic parts inside of the banana jacks are the plungers which activate the detection switches.
The IC in the middle is a PIC microcontroller.  I suspect that it's main purpose is to detect leads, and to control the LEDs under the light pipes.

Mastech MS8268 multimeter with back cover removed. Fuse visible.

ICs in this meter, which I was able to identify
I bought this MS8268 multimeter to measure low currents on the order of units of microamps.  The miltimeter didn't disappoint, considering especially a relatively low price.


Mastech MS8268 review
Teardown video (Dec 15)

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