Confirmed Starting Point
For RS232 communication with a Mastech MAS345 digital multimeter from NI LabVIEW, the confirmed starting point is the serial instrument example that ships with LabVIEW:
\examples\instrsmplserl.llb\Advanced Serial Write and Read.viOpen this VI from the LabVIEW examples directory (or through the NI Example Finder under Hardware Input and Output > Serial). It demonstrates the core pattern an RS232 instrument session requires: opening a serial port resource, writing a command or query to the device, and reading the returned response. Use it as the working template for the MAS345 session rather than building the serial logic from scratch.
What Is Not Established by the Available Evidence
The evidence does not specify the MAS345 serial parameters, cable wiring, or command/response protocol. The following items must be confirmed against the instrument's own documentation before the example VI will return valid data:
Baud rate, data bits, parity, stop bits, and flow control; whether the meter streams readings continuously or responds to a query; the exact request string (if any) that triggers a reading; and the response framing (terminator character, byte count, or fixed-length packet). Do not assume values for any of these — a mismatch on any one parameter produces a timeout or garbled data with no distinguishing error.
Decision Path and Verification
Match every serial port setting in the example VI to the values documented for the MAS345, then run the write/read cycle. If the device is query-driven, send its documented request string and read the reply; if it streams autonomously, perform reads only and parse the incoming bytes. Verify success by comparing the value decoded from the serial response against the reading shown on the meter's display — agreement confirms correct parameters, wiring, and parsing in one check. If the read times out, first re-check the port configuration against the instrument documentation, then confirm the cable type and pinout, before changing any code.
FAQ
How do I communicate with a MAS345 DMM over RS232 in LabVIEW?
Use the LabVIEW example VI Advanced Serial Write and Read.vi as the template. It implements the open-port, write, and read sequence; adapt its serial port settings and command string to the values documented for the MAS345.
Where is the Advanced Serial Write and Read.vi example located?
In the LabVIEW examples directory at \examples\instrsmplserl.llb\Advanced Serial Write and Read.vi, also reachable through the NI Example Finder under the serial instrument examples.
What baud rate and serial settings does the MAS345 use?
The available evidence does not state them. Confirm baud rate, data bits, parity, stop bits, and any terminator or query string from the instrument's documentation, then configure the LabVIEW serial session to match exactly.