Inter Laboratory Comparisons - Baratrons

[Jerry Eldred]

Greetings Everyone (Hi Marc...)...

I have been super, super busy (and still am). I am monitoring posts for anything I can assist with, and look forward to one day down the road when I have more time available for such things.

Now, to my question. Anyone who might be able to assist with this will know what a "Baratron" is (a brand name for a Capacitance Diaphragm / Capacitance Manometer). They are absolute pressure transducers typically in ranges from 0-1 Torr (mmHg Abs) through 0-1000 Torr (remembering that 760 Torr (mmHg) is approximately ambient, and 0 Torr is absolute zero pressure absolute). They typically operate with 0-10 VDC output where the tolerance is % of reading of the VDC output for a given absolute pressure. That is the very abbreviated description for the masses.

I am in process of bringing my system on line for calibrating Baratrons from 0-0.1 Torr through 0-1000 Torr. There are very few vendors who can properly calibrate these. To avoid commercial content, I'll just say one is a high accuracy pressure standards cal lab, and the other is an OEM lab. As I've been bringing this system on line, I've had a few correlation inconsistencies (I won't go into detail). I think I have it pretty well nailed down, and I plan to get accredited for this parameter once I have good documentable confidence in everything (etc..).

One little piece of this puzzle that would help me moving forward is to find a place or places where I can do an Inter-Laboratory Comparison ("Round Robin"). If anyone out there is doing this kind of calibration and would like to participate (I think this is appropriate here, as it is not selling anything).; or if anyone knows of anyone who might have the capabilities in this area and could send me a private message so I could contact them, that would be very helpful.

This is a slow, ongoing project, and it may be a couple of months before I can do much. But I wanted to put the question out there to see what I can find out.

Also, I don't believe there is a proficiency test available on this (I haven't looked yet, but as it is such an oddball..).

 

[Miner]

Can anyone assist with this question?

 

[BradM]

Jerry, I don't know of anyone around here that could calibrate these devices. Helix Technologies in Longmont, CO calibrates our process instrumentation, and they have the equipment to achieve pretty low pressure.

As a matter of fact, I have a Baratron in the box I have never put into use. We were going to verify our own pressure/flow instruments. But we would need to re-plumb the system to achieve steady-state, and that was not going to happen.

Where in Texas are you? Also, the Baratron I'm thinking about is a pretty accurate device; on the order of being a standard. So you would need a lab with equivalent standards, correct? I have process instrumentation, so you would be stepping down comparing the Baratron to what I have seen.

I'll ask around, Jerry, and see what I can come up with.

 

[Marc]

Here's another 'Bump'.

 

[Jerry Eldred]

The standards level Baratrons are 0.05% of reading, and are used to calibrate the lower accuracy baratrons. State of the art is typically less than 4:1 TUR (when you send to MKS for normal cal, the TUR is often around 2:1 or 3:1 - or so). So we are doing normal cals with the system the same way MKS does them.

Matter of fact, if I ever have time to get it done, we recently inherited a VGCS200 system (the large automated Baratron calibrator). I have some plumbing work to do on it, and need to replace one of the mechanical pumps to get it on line (and a bunch of other stuff). BUT... I am preparing for my upcoming ISO17025 audit now, so no time for such fun stuff.

I am back in the Austin area again and loving being back in Texas.

As for who can calibrate them there are only a handful of labs in the U.S. who can calibrate the standards level baratrons (including the OEM). The kinds of labs that can cal very high accuracy pressure standards (such as DH Instruments, etc.) are among those who can cal them.

I was a little curious to see if any other independent labs such as mine were out there with such capability, who would perhaps care to join an ILC on these. Even on the A2LA website, I found only a few labs with any capabilities, and mostly not as accurate as mine (I have the standards type baratrons - 0.05%, ranging from 0.1 to 1000 Torr ranges). I found a couple of labs who listed the kind of baratrons that I calibrate as their standards. I am, by the way, not accredited in this - still developing this area. We are calibrating them for some established customers who we meet their quality systems criteria; but not for the accredited world yet.

This was one of the reasons I wanted to find someone who can do an ILC. To my best knowledge, I don't know of any PT's for these.