New generation Celani wire experiments. UPDATE2: Measuring the flow

It is with great pleasure that we finally have the opportunity to test the latest generation of Celani wires.

These are the electrically/joule heat cycled, knotted, at chemically treated wires that are sheathed and bound.

Mathieu has worked hard to prepare everything for this series of experiments, which will include testing in the standard active and control dual Celani cells and the now calibrated and instrumented MFMP Mass Flow Calorimeter (MFC). The Celani cells will predominantly be looking for signs of Gamma emissions, the MFC will be looking for any signs of excess heat.

You can get up to speed and keep up to date by following the live document published below. The live data will be published into this public folder.

Thank you to all our generous donors over the past two years that have made construction of the MFC possible. Thank you also to National Instruments for provision of the DAQ and LabView License.

UPDATE: Understanding the Flow-Control

I keep saying to people it is too early to say, but we have passed the P&F milestone of skepticism.

History keeps repeating, in March 1989, Stanley Pons and Martin Fleischmann did exactly what we are doing with Live Open Science. They opened the door of public knowledge about their discovery to the general public, and soon after the crowd was rejecting what was brilliant piece of calorimetry. Much better than what we are dealing with right now by the way. Their system was so precise that solutions of specific differential equation were necessary but never done at their time! They truly revolutionized calorimetry at the same time.

To get back to our matter, there is much difficulty to get everything explained in a single comment lost in the discussion. So here I am.

In flow calorimetry, flow is as much important as reading temperature. And only scientists who are trying to resolve the hundredth of a degree with precision and repeatability are able to tell you how hard is that. Well, it is the same for flow control.

I got in contact with Arik El-Boher from university of Missouri in June 2015 on matters about flow control because I knew this is an important part of the system. His technician and himself were very much encouraging about the use of a Bronkhorst L30. One plot is better than tons of discussions. There is the graph they sent me:

...just look at the numbers on the time scale (X-scale), I think it is in minutes.

A quick quote on phone with their available commercial in Paris gave me the public price of such equipment. This was way over any possible affordability for the project. So I wrote to them and other manufacturers, competitor on the market. It was about the mass-flow calorimeter, the project, my work, our field of research, Live Open Science and how we can work together. Even thought I had two replies, their answer was the one positive.

After few exchange and discussions we agreed on satisfactory terms. That would imply spending time on counseling to their engineers. This is ongoing, and a very fruitful collaboration is born.

The system is not a pump, the moving part is a valve placed behind a flow-meter. You have to supply pressure to the system to make it working. To do this I used the integrated pump inside the cryostat to supply sufficient pressure. Additionally, it measures the flow rate using the thermal expansion of the fluid. Precision is 1% but repeatability is 0.2%. Repeatability is the characteristic here. If we want to have the right comparison between calibrations and the test, this plays a key role.

When I received the system, it was simple and straightforward to put in operation. Supplying 24V to the logic board, then connecting RS232 and running the provided VI showed me how much this controller is the Roll-Royce of flow control. Variations were just imperceptible on the front panel of the program. Then I implemented key parts of the virtual instrument in the main program that runs the calorimeter. Within the program I had to increase the number of decimals to 10^-5 to see any decimals in the readings.

The tricky part was to make sure the normally closed valve wouldn’t completely close when the program stops or crashes. This way the heat doesn’t accumulate in the calorimeter and boils off if for an unknown reason the power supply keep delivering power, or worse “heat after death”.  :)

I had knowledge of my future lab’s situation only few days earlier, and I was not able to push tests and characterization of the flow-controller further on. But I kept in mind it was necessary to have other means of back-checking that crucial part of the system. So I did the calibrations using the reading coming straight from the logic board through RS232.

After the calibrations and during the loading, it was possible to modify the program, so I added the analog voltage reading to my DAQ, in place of the previous flow-meter used.

Using the integrated 4-wire resistance reading from the DMM was also a great improvement done while the wire was loading hydrogen. And yes, it loads hydrogen, because we saw evidence of pressure lowering while the resistance changes, while the temperature of the chamber changes. Everything correlates and will be published in a paper. Actually, this is already an exciting part of this test because we had so many questions and wonders on how we should interpret the resistance changes. This was the main question we came back with from ICCF18.

Back to the flow.

When the DAQ got the flow-metering input, I quickly set up the voltage input, but also quickly put a scale to the measurement. This DAQ is programmed with DAQmx from National Instruements’ LabVIEW and it requires use of a scale where you just put the signal-in type and amplitude and the scaled output.

The objective was not to provide proper measurements; it was in the first time necessary to check the correlation in variations and amplitude between power output and the 10V ouput. Secondly, it would provide backward information for later calculations. Hence this values are wrong, because not properly scaled-up, but they hold the pattern of a variation.

The DAQ provides noisy signals and need to be check-up. At the last minute, it was necessary to change the pressure gauge form an older one used for Celani’s tube cells that, I think, perturbates other signals on the DAQ. In the future, it will be necessary to use something like a cold cathode gauge, able to resolve pressure between 10^-7 mbar to 1.5 bar since I won’t work with higher positive pressure again.

To summarize, I am only trustful of the RS-232 reading coming from the program than the DAQ measurement. And this for three strong reasons:

1. I tested the VI, saw it working and extracted the code from it, it works.
2. I didn’t properly set the DAQ, hence readings are unscaled and should be disregarded
3. The DAQ might be damaged or gets perturbations from the pressure gauge.

Additionally, there is no reason to consider using the values of DAQ flow-meter for a direct calculation, simply because they were not used for the calibration. During calibration, only the RS-232 input was connected, so it was reading the value of the flow-controller coming straight from the logic board.

If the measurements from the RS-232 during our test are wrong, so do the calibration values. Repeatability is very good on this instrument, so the systematic error would have take place on the power output calculation of the calibration.

“It is not because you don’t look at something that there is no problem”. That is why I added an additional 10V reading. I took the risk of showing wrong values to our followers, but I conservatively wanted to store as much data as possible. In case when I check the flow-meter after the test, the graduated flask or the scale shows me a wrong quantity of mass displaced during the measurement.

With all the surprise to show a positive excess energy value on the first experiment, I must say that if something is wrong, it will be assessed and it will be characterized properly after the test. Further update will share the details of these verifications.

I didn’t do this experiment because I was 100% confident in the calorimeter otherwise if would have take me 3 more months of my personal time; I did it because I was confident in its capabilities to characterize the material and assess indication of energy within the given time I have. This is the reason why I am confident, but very prudent.

Thank you for taking the time to read that.

UPDATE2 : Measuring the flow

After an issue with flow measurement was questioned by one of our follower, between the different instruments readings, additional verification of the flow control setup are done locally on Feb 6th. Three measurements of the flow using a graduated flask and a scale shows results of 130,05 g/min, 127,63 g/min and 129.44 g/min. This is lower than the requested value of 150 g/min.

Finding the origin of the issue was not obvious at first. But when I remembered the switch behind the cryostat head, this hinted the origin of the problem. This switch is setting the flowrate of the cryostat pump. Since this pump provides the pressure necessary for the flow-controler to control the flow, it was the best candidate to be the cause of the problem. Because it was on the lower flow setting it was not providing sufficient pressure to the controller. Hence explaining also the disparities on the analog readout, mainly because Kv factor of the valve was not calibrated to the condition imposed by the setup. Flipping it to the higher setting corrected the problem within few minutes, bringing it back up the requested command of 150 ml/min within a ±1ml/min variations on the analog output.

To keep going with the current run and avoiding disparities with our current calibration, the average value of the analog measurements is used from a very large sample population. The result is 128.177 ml/min. The scale applied to the analog output is verified and should give proper results, variations are within a tenth of a percent from our previous measurements. However, with a standard deviation of 4.86 ml/min, this value lowers by 3.8% our confidence of the current run to previous calibrations. We will have to wait new a calibration, that will be published after the test, to have a better assessment of the results.

On a personal note, this proved me not to trust the program and the given tools. I did log the analog out for this very reason, but it was not showing the right calculation since the beginning of the test. The only conclusion is to avoid making wrong or awkward assumptions until we have ruled all the potential problem that are potentially occuring on the system. As I said before, I am very surprised to have positive results on the first run. It is very likely later calibrations cancel any positive results.