Mettler Toledo WXS205SDU Balance Zeroing Issues on Tecan Freedom Evo, but not on Hamilton Vantage

UCantBcereus · January 19, 2023, 8:50pm

Hi all! Our team has been having some issues with extreme drifting/zeroing issues our Mettler Toledo WXS205SDU Balance that we wanted to use for volume verification on both Tecan Freedom Evo Platforms and Hamilton Vantage platforms that we have.

We bought the Liquid verification Kit (LVK) from Hamilton, which includes the Balance, a temperature/humidity reader, a display, LVK software, Hamilton carriers, weigh pans for various tube adapters, as well as a weigh pan to fit SBS plates. We then bought the integration kit from Tecan, which includes Tecan specific carriers.

After figuring out how to change communication settings (not straightforward; Tecan really needs to update their manual from 2007), we are able to successfully communicate between the Mettler Balance and both the Hamilton Vantage and the Tecan Freedom Evo. We can successfully use the tube weigh pan with no issue on both platforms; the mass stabilizes and allows zeroing after a minute or so.

The big issue we have now is with the SBS plate weigh pan. On the Hamilton Vantage, we have no issue with the mass drifting (maybe ±0.2-05 mg); although oddly enough we get less drift when do not use the acrylic cage/cover that is also provided in the kit to prevent air disruption. On the Tecan Freedom Evo platforms, the SBS plate weigh pan takes hours to stabilize. The mass will start off drifting (in either the positive or negative direction) ~1 mg/sec, eventually slowing and stopping after 1-2 hours. This long amount of time to settle makes testing volumes with the MCA96 head not practical.

To make this even more confusing, we happened to have Hamilton in to do a PM while we were having this issue. We hypothesized that perhaps there was something wrong the SBS plate weigh pan. We took the Service Engineer’s SBS plate weigh pan, and put it on our LVK scale while it was connected, and had no drift issues. However, we then had no issues when we put our SBS plate weigh pan on the scale. Fast Forward a few weeks, and the issue has returned. All of this is with the acrylic cage/cover on it that should theoretically stop air disruption.

Other notes about the environment:
We have Two Tecan Freedom Evos, each on separate floors, but in large lab spaces. Both have enclosures, although one has a larger hole in the locking door than the other. Blocking off the hole in front of the door with a lab diaper seems to help. The scale sits 7 inches front of the instrument on its Tecan carrier.
The Hamilton Vantage is in a small enclosed room, where the air flow is noticeably more stagnant. The scale sits 10 inches back form the front of the Hamilton on its carrier.

Has anyone else ever seen this issue? Does anyone successfully use the SBS plate adapter on the LVK kit on a Tecan platform? Thanks everyone for being so helpful, this forum has become a daily read for me!

luisvillaautomata · January 19, 2023, 9:03pm

@KevMcGuire_Tecan
@Optimize
@MikeMueller

I wonder if you’ve seen this issue on an EVO.

KevMcGuire_Tecan · January 19, 2023, 9:37pm

Let me check with my team. I’ll get back to you.

Optimize · January 19, 2023, 9:45pm

this is v curious
if you sit the balance NOT on the Tecan deck, and just on a separate lab bench - does it exhibit the same behaviour ?
balances, as we know, are v sensitive to vibrations & air flow - removing the enclosure air flow & possible vibrations of the EVO deck itself should allow you to identify if the issue is location based

next, try without the SBS pan and see if that improves the settling

i’ve used integrated balances a lot on a variety of instruments - vibration and settling take a little time, but not hours (not minutes, maybe 2-3 seconds)

KevMcGuire_Tecan · January 20, 2023, 2:20pm

Feedback I got:

As far as I understand is the problem not always there.
Drifting from a balance is normal and will be increased if you put a plastic plate or cup on the balance.
This is because of static electricity on the plastic.
You can use a antistatic gun to eliminate the electricity or a plastic antistatic bag.

Similar behavior to when you encounter static while picking up or disposing of disposable tips. For a balance it is the same approach.

Worth a try.

UCantBcereus · January 20, 2023, 8:55pm

Hi All,

Thanks for the feedback @KevMcGuire_Tecan @Optimize , and thanks @luisvillaautomata for tagging the right people!

So we did some testing today to try and clarify this further. We did more testing of the scale inside our Vantage, on a bench directly outside our Vantage, inside 1 of our 2 Tecan Freedom Evos, and directly outside the Freedom Evo on a nearby bench. We tested this with feet attached (needed for the Tecan carrier), with the feet not attached (necessary for the Hamilton carrier). We tested both the tube and plate adapter again. A Quick Summary of the results are below:

We did find a way to resolve the taring issue on the Tecan. The Tecan carrier fits in a such a way that puts the scale 7 inches away from the front of the deck, compared to the Hamilton carrier. We popped out the 3 pronged inserts in the deck, and set the carrier further back (MCA96 could still reach in this position). This meant the balance was now ~10.5 inches from the front of the deck. When trying to Zero, we were then successfully zero with both the tube and the plate. So the 3 inches extra depth made a huge difference!

We will try next week on our other Tecan to see if its reproducible. We also were still getting worse results with the plastic cover/draft shield that comes with the LVK kit, so we are planning on purchasing a static gun as suggested, and seeing if that will allow us to discharge the static and use the draft shield as intended.

We will update when we can do all the tests. Thanks again all for the ideas; Mettler hasn’t been super helpful when I have talked to their support team, as they say its Hamilton’s responsibility, but Hamilton has told us that they won’t help if there is not an issue on the Hamilton specifically. We had a great help from a rep at Tecan to get the Balance communicating properly, but Tecan doesn’t sell that SBS plate adapter, so they were unsure why we were seeing those issues. This problem falls exactly inside that gray area where a forum like this is truly helpful!

luisvillaautomata · January 20, 2023, 9:21pm

Silly Question but are your liquid handler systems level?

Are the decks uniformly level?

I’ve had issues in the past with unlevel systems and then parts of the deck that actually seemed to bow a bit.

EricSindelar_Hamilton · January 21, 2023, 3:23pm

Sorry if you have tried this already, but you can download and use the Mettler APW Link software to connect and adjust settings on the balance. With the software, you can adjust the environmental setting to be “very unstable,” adjust the readability to use fewer significant digits (which would improve the robustness of the reads, but of course isn’t ideal if you are testing lower volumes), modify the weigh reading, etc.

We certainly see more issues with balance behavior during the dry, winter months. Anything you can do to increase the humidity and decrease the influence of static and air flow would help! As you stated, the plastic shield could be a culprit with static so you may want to mock up a draft shield using other materials (arts and crafts time in the lab!) or invest in some anti-static solutions as you alluded to. That wouldn’t really explain why it works on the Hamilton and not the Tecan though.

I hope some of this is helpful!

-Eric

UCantBcereus · January 23, 2023, 5:03pm

Hi All. Wanted follow up on the final testing we did today on the 2nd Tecan Freedom Evo we wanted to test this on.

@luisvillaautomata I did confirm that all 3 liquid handlers are level!

@EricSindelar_Hamilton Thanks for the additional feedback! We do have the AWP Link software downloaded, and have used that to change some settings previously (note that we did have issues changing the communication settings through this software, and needed to use our terminal display to get the changes to stick, in case someone stumbles onto this later). We adjusted the environmental settings to “very unstable”, and that seemed to decrease the noise a lot. We are going to invest in some anti-static solutions (will be useful for other liquid handlers we have), but if we need something in a pinch we can fabricate something. Interestingly though the driest room is the Hamilton room where it originally worked best.

Below is a screenshot of our results from our testing.

This Tecan Freedom Evo is the closest to an air vent, and has a more open front door shield. This is also in an “open concept” lab, but the

The biggest things that we did to get improvement was:

Change to Very Unstable Environment Setting
Set the Balance further back in the Tecan (pop out the 3 pronged inserts to allow inserting the Tecan balance carrier further back). The difference of being 10 inches from the front vs 7 inches makes all the difference, especially if you don’t have the environment set as “very unstable”.

When we get the anti-static device, we will attempt the test again with the plastic draft shield, and will confirm that fixes that issue too.

Thank you all for the constructive feedback everyone!

UCantBcereus · January 25, 2023, 6:25pm

Hi all. Just wanted to post one last update on this. We got an anti-static gun in, and used that on the plastic cage/cover that comes with the Hamilton LVK kit. That immediately reduced the wild drifting that occurred.

So all in all, in case someone stumbles on this in the future, the 3 biggest changes that helped the most were:

Remove static electricity
Change environment to “very unstable”
Increase depth of where the balance sits on the deck

We are happy with how things are working now, and can now proceed forward with some volume verification projects that we need to do. Thanks again all for the help!