Communicating with a Fluke 787 Processmeter

[Dexter_Bunco]

So here's a new one on me. I'm a Met/Cal procedure writer so I'm always looking for ways to remote interface with equipment to automate calibration as much as possible. Well, a Fluke 787 Processmeter crossed my desk and while I was browsing Fluke's procedure database, I came across a procedure to communicate with this unit via RS-232. So I looked the meter over and couldn't find any communication ports. I opened the battery compartment and couldn't find any pins. So both stumped and curious, I download the scripted procedure and dove into its code. In the header, it mentioned a dedicated calibration module. Because blasted Fluke changing communication interface... *@#$% fraking %## frak #$% bought enough $%@$ adapters already*

Anyway, I look up this calibration module (link below) and I discover the RS-232 cable connects to it and I figured that this must just be PC controlled switcher or something. But reading Flukes description of this module is what's really bizarre.

"Application: The calibration module provides a 9 volt dc supply to the 787. At the same time, it facilitates RS232 communication from the PC running MET/CAL to the 787 over the battery leads of the 787."

So... It's communicating over the battery leads?! How the heck does that work?? I've heard of using wall AC as a carrier wave for digital signals (poorly) but this is something completely off the maps for me. Has anyone else ever seen this? Has anyone ever successfully communicated with one of these meters before? Could I make one without giving Fluke another grand for a stupid proprietary communication adapter?

The questions aren't really all that important. I have just never seen this before and wanted to share.

Link to the calibration module:
https://www.fluke.com/en-us/product/accessories/other/fluke-787cal

Edit 1: Here's a link to its image as Fluke doesn't have a product picture for some reason:
https://images.app.goo.gl/KvPgjpkxxYz7AGDw7

[MosherIV]

Hi. I think you will find the 787 has a hidden optical port on the top.
Look at the picture from the link
https://www.cetm.com.my/product/fluke-787-and-789-process-meter/

[Dexter_Bunco]

Must be something new, because this one sure doesn’t have that.

[MosherIV]

Yes. Looks like Fluke havd revised the design and based it on the Fluke87V case.
The previous design was based on the case for 187/189 which does have the window for the optical link. I do not think the 87V has data link, I do not have one to chdck.
Either Fluke have confused documentation or the document you have is for the older model.

[Dexter_Bunco]

I guess I am not really following you here. The picture you showed me at this site:

https://www.cetm.com.my/product/fluke-787-and-789-process-meter/

Is of a 789, not a 787. The third picture on that site is of a 787 which looks exactly like mine, case and all. The documentation for my 787 says it communicated with my 787 via RS-232 through it's battery leads using a fluke specific module. I found the fluke specific module on Fluke's website.

My post was just commenting how weird that was and that I've never seen that before.

Not sure what you are referring to regarding the 87V other than the cases look similar.

[MosherIV]

Good point. I had not noticed they have 2 models and pictures of each.
Google just showed the first picture and I assumed it was a 787.

The 789 case is based on the old 187/189 (previously 87IV and 89IV), both not discontinued.
The 787 case is based on the 87V. Since the 87V does not have the optical data link, I guess they had to get creative when getting a data link for the 787.

My mistake 

[Dexter_Bunco]

No worries.

My roommate smells conspiracy though. Save $3/unit on a dedicated comms port and charge for the comms module at profit.

Either, very curious design.