MASTECH MAS345

The MASTECH MAS345 is a 3999 counts, CAT II handheld digital multimeter with RS232 connectivity.

It is also sold under the names Velleman DVM345DI, McVoice M-345pro, and Sinometer MAS345.

Software: "DMM VIEW" version 2.0 (from ELV; for Win98/NT/ME/2000/XP; supports MAS343, MAS344, MAS345, M9803R)

See MASTECH MAS345/Info for more details about the device.

Hardware

Multimeter:

Main chip: MASTECH Japan M343-01 F0951D174 (80 pins, 16 + 16 + 24 + 24)
?: ST 74HC4060 N00U732
?: Texas Instruments 12AL9JM 0P07CP
?: GC7555AP AA7057HS
?: Sharp B B5 PC817
?: Sharp B B6 PC817
Crystal: ca. 32kHz
Fuse: 15A/250V (6x30mm) (for the 10A jack; interestingly the PCB silkscreen says "20A" for that jack)

RS232 cable:

TODO.

The protocol is documented in the vendor software's "Help" window (seems to apply to MAS343, MAS344, and MAS345; the M9803R protocol is different).

Serial port settings: 600 baud, 7n2
Every time the host sends any character to the DMM, it returns 14 ASCII bytes containing the measurement value and so on. The documentation states that a request interval of >= 1 second is "required for stable measuring data from meter".

Byte(s)	Description
1-2	Measuring mode: DC, AC, OH, CA, TE, ...
4	Sign
5-9	Decimal point and current measurement value. Examples: "10.00", "0L", "3.999".
10-13	Unit. Examples: mV, A, KOHM, nF, ...
14	Carriage return

TODO.