MASTECH MAS345
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The MASTECH MAS345 is a 3999 counts, CAT II handheld digital multimeter with RS232 connectivity.
It is also sold under the names Global Specialties Pro-70, Velleman DVM345DI, McVoice M-345pro, and Sinometer MAS345.
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)
- 14-stage binary counter/oscillator: ST 74HC4060 N00U732
- Precision Operational Amplifiers: Texas Instruments 12AL9JM 0P07CP
- ?: GC7555AP AA7057HS
- Opto Coupler: Sharp B B5 PC817
- Opto Coupler: 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
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, RTS low, DTR high
- 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
- Original English vendor manual (2008)
- elv.de: Download zu: Digital-Multimeter MAS-345 (68-04 59 88):
- German manual from ELV (2002)
- "DMM VIEW" software, version 2.0 (for Win98/NT/ME/2000/XP; supports MAS343, MAS344, MAS345, M9803R)
- cczwei-forum.de: C# software for reading DMM values