According to Scott at Digital Aquatics, they are working on a ground loop isolator for the RK2. I haven't tried it, but you could probably (at your own risk) give the one Neptune sells a try. On the Digital Aquatics forum on RC, Scott said they are trying to keep the price under $20, which would be cool.
I did some testing on my Dell Inspiron 8000 (DB9 Serial connector) and my Dell Inspiron 1705 (USB-Serial DB9 connector). My findings were:
The data connection from the unit uses 3 wires of a 9-pin DB9 Serial connector. It uses wires 2, 3, and 5 which are receive, transmit, and ground, respectively.
On an actual serial connection (i.e. not a USB to Serial adapter connection) to a DB9 port on a computer, only wire 3 actually needs to be monitored to get the data. Bad news is that it still gets a ground loop problem due to relative differences in voltage. Enabling/disabling the other 2 wires affects nothing.
Through a USB-Serial adapter, it requires all 3 wires and has the ground loop problem. Disabling wire 2 or 5 causes garbage to come over wire 3.
From my research and e-mailing Scott, it is a ground loop issue with the signal. I looked into getting optoisolators to make an isolator for it, but haven't been able to find any locally or any real specs on ones via mail order. Pre-built lab grade isolators can be had starting at around $60. These isolate all 9 (or all 25, if you get a DB25 version) pins.
Alternatively, I did find at least on my connection that I did not get any ping-ponging. The pH jumped, but then re-stabilized around 3 points higher than normal. I tried recalibrating with the computer connected and that worked. I do NOT suggest this as a real solution, though, because I have no idea what if anything it does to the equipment through the loop long term. I point this out for those that for whatever reason have money to risk needing another RK2, but not enough to burn on an AC3.
Another possibility you could look into and worth it from a coolness/utility standpoint is getting a Bluetooth serial or USB connection to the computer. This will also isolate the grounds from each other while providing the additional functionality of not having to tether a computer to the setup.
Scott indicated that they were hoping to have a solution testing starting this week, but with the 4th, I wouldn't hold my breath.
I did some testing on my Dell Inspiron 8000 (DB9 Serial connector) and my Dell Inspiron 1705 (USB-Serial DB9 connector). My findings were:
The data connection from the unit uses 3 wires of a 9-pin DB9 Serial connector. It uses wires 2, 3, and 5 which are receive, transmit, and ground, respectively.
On an actual serial connection (i.e. not a USB to Serial adapter connection) to a DB9 port on a computer, only wire 3 actually needs to be monitored to get the data. Bad news is that it still gets a ground loop problem due to relative differences in voltage. Enabling/disabling the other 2 wires affects nothing.
Through a USB-Serial adapter, it requires all 3 wires and has the ground loop problem. Disabling wire 2 or 5 causes garbage to come over wire 3.
From my research and e-mailing Scott, it is a ground loop issue with the signal. I looked into getting optoisolators to make an isolator for it, but haven't been able to find any locally or any real specs on ones via mail order. Pre-built lab grade isolators can be had starting at around $60. These isolate all 9 (or all 25, if you get a DB25 version) pins.
Alternatively, I did find at least on my connection that I did not get any ping-ponging. The pH jumped, but then re-stabilized around 3 points higher than normal. I tried recalibrating with the computer connected and that worked. I do NOT suggest this as a real solution, though, because I have no idea what if anything it does to the equipment through the loop long term. I point this out for those that for whatever reason have money to risk needing another RK2, but not enough to burn on an AC3.
Another possibility you could look into and worth it from a coolness/utility standpoint is getting a Bluetooth serial or USB connection to the computer. This will also isolate the grounds from each other while providing the additional functionality of not having to tether a computer to the setup.
Scott indicated that they were hoping to have a solution testing starting this week, but with the 4th, I wouldn't hold my breath.
