V&A VA18B
The Mastech VA18B a.k.a. V&A VA18B (V&A is a brand of Mastech) is a CAT II (1000V) handheld digital multimeter with USB connectivity.
See Mastech VA18B/Info for more details (such as lsusb -vvv output) about the device.
Model overview
It seems there have been at least two different revisions of the multimeter (or at least of the PC-Link cable). The older one used a Sunplus SPCP825 USB-to-serial chip (see here, here, or also check the drivers from here), the newer revisions use a Prolific PL2303 chip. Both should work fine with sigrok, as long as the respective driver creates a "virtual COM port" / serial port device sigrok can connect to.
| Device | Rebranded? | PC interface chip | Vendor software | Comments |
|---|---|---|---|---|
| Mastech VA18B (old) | no | Sunplus SPCP825 | "PC-LINK" | Manual: VA18B.pdf |
| Mastech VA18B (new) | no | Prolific PL2303 | "PC-LINK" | Manual: VA18B.pdf |
| Velleman DVM1200 | yes (VA18B) | ? | "PC-LINK" | — |
| Maxwell MX-25328 | yes (VA18B) | ? | "Maxwell Universal Program" | Maxwell wrote their own PC software, apparently (works fine with the VA18B if you select "25328" as device in the software). |
| Peaktech P3375 | likely (VA18B) | ? | ? | Very likely a rebranded Mastech VA18B (1, 2, 3). |
Hardware
Multimeter:
- Main chip: Unknown, it's very likely a bare die under the black blob (see photos).
- Display: ?
- Precision, very low power, CMOS dual opamp:: 27L2C U85T CN58
- ?: 7530-1 1129
- Crystal: 4MHz
- Fuses: 750mA/600V (5x20mm), 10A/600V (6x30mm)
USB cable:
- USB to serial chip: Prolific PL2303HX YR0903A
- Crystal: 12MHz
Photos
Package, front
Package, back
Package, contents
Device, front
Device, back
Device, open 1
Device, open 2
PCB, front
PCB, front, 1
PCB, front, 2
PCB, front, 3
PCB, back
27L2C
7350-1
Crystal
USB cable
USB cable PCB, front
USB cable PCB, back
Protocol
14-byte LCD segments over USB-2-serial (Prolific PL2303 chip, 2400 baud, 8n1), see various links below.
To enable output to the PC on the multimeter you have to keep the Hz/DUTY key pressed while powering on the device. However, it will auto-poweroff after roughly 1 hour, even in this mode. To avoid that, press both the Hz/DUTY and the SELECT key during power-up (see manual, page 9, section 2.3.1).
Resources
- Protocol descriptions: [1], [2], [3]
- EEVblog forums: Product review: DMM latest V&A Mastech VA18B