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.

Manual: Original version (2008), German version from ELV (2002)

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.

Photos

TODO.

Protocol

The protocol is (partially) 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, DTR on
• Every time the host sends a (any?) character to the DMM (the vendor software sends D/0x44), 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".

Packet format:

Byte(s)	Description
1-2	Measuring mode (DC, AC, OH, CA, TE, DI, ...)
3	Always a space (?)
4	Sign ('-' or ' ', i.e. a minus or a space)
5-9	Decimal point and current measurement value (Examples: 10.00, 0L, 3.999)
10-13	Unit (Examples: V, mV, A, mA, kOhm, MOhm, nF, ...)
14	Carriage return (13/0x0d)

Example packets:

01	02	03	04	05	06	07	08	09	10	11	12	13	14
D	C		-	0	0	0	.	0				V	\r
A	C			0	0	.	0	0				A	\r
C	A			0	.	0	7	1			n	F	\r
O	H				O	.	L		M	O	h	m	\r

Resources

• elv.de: Download zu: Digital-Multimeter MAS-345 (68-04 59 88) (German manual, software)