V&A VA18B

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Mastech 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 PL2303HX 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 PL2303HX "PC-LINK" Manual: VA18B.pdf. PCB silk screen: "VA18B 20070302".
Amarad Hellas Electronic VA18B yes (VA18B) ? ? See also this photo. PCB silk screen: "VA18B 20070302".
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

Multimeter:

  • 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

  • USB cable PCB, front

  • USB cable PCB, back

Protocol

14-byte LCD segments over USB-2-serial (Prolific PL2303HX 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

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