Serial Interfaces on Lab Balances

I’ve hooked up one of our lab balances to a PC!

For users of the Geography Laboratory

In the main lab is a networked computer that I’ve connected to the Ohaus Adventurer AR-Series balance. To use it:

  • login
  • open “C:\SPDC Data Collection V2.01\SPDC Data Collection V2.01.exe”
  • click “Browse”, find the Excel spreadsheet you want to import to, and click “Open”
  • click “Run”. It will automatically open the spreadsheet and connect to the balance
  • select to cell you want to populate, and press the “Print” button on the balance; it will populate the cell with the current reading.

How’s it Done and Can You Do This With Other Balances?

Almost all laboratory balances have RS232 communications built in as standard, but for some reason they seem to want to make it as hard as possible to use them! This is unfortunate, because this functionality is really handy for connecting them up to spreadsheet packages like Excel for automatic data entry. If you can get it working, it is an easy way to save all your lab users time and reduce transcription errors. I’ve had a good hack at the Ohaus balances in our lab, and here are some notes on my experiences. My next project will be to pipe these serial connections over IP, and then allow access via a WIFI hotspot. Just connect to the WIFI hotspot, start the wedge software and measure away – well that is the plan, anyway.

Ohaus Adventurer AR-Series (like above)

These should be straightforward – they have configurable Rs232 communications and a standard male DB-9 connector. Of course, for reasons best know the the manufacturer, they have completely non-standard pin assignments. The pin assignments are shown in the manual, so you’ll have to build your own null modem cable to connect it, or the ground ends up connected to the CTS and you get nonsense. On the plus side, Ohaus supply the wedge software for free, which will allow direct input into a .xlsx, .csv, etc. The standard serial settings are 2400 7N2 (yeah, why not?), but these are configurable so you could change them to something this side of sensible (like 9600 8N1). Once it is all up and running, just press “print” to fill a cell.

Ohaus Explorer (& Pro)

Now here’s a thing: although the pin assignment and default serial settings are the same as for the Adventurer series, the RTS/CTS is implemented differently. No problem, just set the correct flow control in the wedge software, right? Well, we would if we could, but the Ohaus wedge software doesn’t implement hardware handshaking properly! Open a serial connection using Minicom or PuTTY and you’ll have no trouble sending and receiving (when you configure the handshaking properly), but try the Ohaus software, and it won’t play. You’ll have to tie the CTS and DTR pins together to get them to work – it’s a bit ham-fisted, but it’ll do. This will be my next project.

Mettler Toledo 

Naturally, Mettler Toledo fit a serial interface without the familiar DB-9 connector. I’m working on sourcing it, but I suspect it’ll be £££.


Haven’t started on these yet, because we don’t have many in the labs, although previous experience tells me they are usually good at implementing serial comm’s over RS-232.