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Hi Whit,</div>
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That's what the Dwyer rep said when I called to ask what the difference between the psig and psia sensors were for that model.</div>
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I'll try again via email so we have some sort of paper trail.</div>
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Honestly this isn't the sensor I would have selected if we had known about the absolute pressure requirement, most of the gaseous detector systems we deal with in Hall B use differential ones, or maybe gauge. These sensors were selected well before that was
changed later on in the development process.</div>
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<div id="divRplyFwdMsg" dir="ltr"><span style="font-family: Calibri, sans-serif; font-size: 11pt; color: rgb(0, 0, 0);"><b>From:</b> Armstrong, Whitney R. <warmstrong@anl.gov><br>
<b>Sent:</b> Thursday, January 16, 2025 9:11 AM<br>
<b>To:</b> Brian Eng <beng@jlab.org>; dsg-hallb_gas@jlab.org <dsg-hallb_gas@jlab.org><br>
<b>Cc:</b> Whitney R. Armstrong <whit@jlab.org><br>
<b>Subject:</b> [EXTERNAL] Re: [dsg-hallb_gas] AHDC gas control</span>
<div> </div>
</div>
<div style="font-size: 11pt;">Hi Brian,<br>
<br>
I am sorry but I do not think the pressure transducer is an absolute measurement.<br>
<br>
Dwyer 626-06-GH-P1-E4-S<br>
<br>
Can you please verify that it operates as you describe? Does it really have an absolute offset, because I am not seeing this anywhere in the manual/specs.<br>
<br>
Thanks,<br>
Whit<br>
<br>
________________________________________<br>
From: Brian Eng <beng@jlab.org><br>
Sent: Wednesday, January 15, 2025 5:01 PM<br>
To: Armstrong, Whitney R.; dsg-hallb_gas@jlab.org<br>
Cc: Whitney R. Armstrong<br>
Subject: Re: [dsg-hallb_gas] AHDC gas control<br>
<br>
Hi Whit, Answers are interleaved below in blue. From: Armstrong, Whitney R. <warmstrong@ anl. gov> Sent: Wednesday, January 15, 2025 5: 26 PM To: Brian Eng <beng@ jlab. org>; dsg-hallb_gas@ jlab. org <dsg-hallb_gas@ jlab. org> Cc: Whitney<br>
ZjQcmQRYFpfptBannerStart<br>
This Message Is From an External Sender<br>
This message came from outside your organization.<br>
<br>
ZjQcmQRYFpfptBannerEnd<br>
Hi Whit,<br>
<br>
Answers are interleaved below in blue.<br>
<br>
________________________________<br>
From: Armstrong, Whitney R. <warmstrong@anl.gov><br>
Sent: Wednesday, January 15, 2025 5:26 PM<br>
To: Brian Eng <beng@jlab.org>; dsg-hallb_gas@jlab.org <dsg-hallb_gas@jlab.org><br>
Cc: Whitney R. Armstrong <whit@jlab.org><br>
Subject: [EXTERNAL] Re: [dsg-hallb_gas] AHDC gas control<br>
<br>
Thanks Brian.<br>
<br>
Marc,<br>
<br>
I have a few more questions.<br>
<br>
1. I am still confused about this offset.<br>
Is the transducer reporting an absolute pressure minus a fixed absolute offset? That seems odd to me.<br>
<br>
Sort of, the only difference between a psig and psia output is what the zero reads at, either right at vacuum or 1 atm. This particular sensor the 0 psig output is equal to 14.7 psia. We don't use this offset anywhere in the software though, the only conversions
done are to convert the 4-20 mA output to mbar (rather than the native psig output of the sensor).<br>
<br>
You'd need a differential pressure sensor to have it referenced to a changing atmospheric pressure.<br>
<br>
2. Also, where is the ambient pressure transducer located?<br>
<br>
The ambient pressure is part of an existing Hall B setup and not done with any new hardware specific to ALERT. It is on the Forward Carriage Level 1, at the top of a rack there so roughly beam level.<br>
<br>
3. What are the pid loop inputs for the automaitc mode? Average pressure, just one transducer or something else?<br>
<br>
Just one transducer is used at a time, the PID input can be toggled between the two on the buffer tank. IIRC Bob added this for redundancy purposes.<br>
<br>
Thanks,<br>
Whit<br>
<br>
<br>
<br>
<br>
<br>
Whitney Armstrong<br>
Assistant Physicist<br>
Physics Division<br>
Building 203<br>
<br>
Argonne National Laboratory<br>
9700 S. Cass Ave. | Argonne, IL 60439<br>
630-252-5112 | 717-341-1080 mobile<br>
warmstrong@anl.gov<br>
<br>
________________________________<br>
From: Brian Eng <beng@jlab.org><br>
Sent: Wednesday, January 15, 2025 4:14:13 PM<br>
To: Armstrong, Whitney R. <warmstrong@anl.gov><br>
Subject: Fwd: [dsg-hallb_gas] AHDC gas control<br>
<br>
This Message Is From an External Sender<br>
This message came from outside your organization.<br>
<br>
I’m not sure you got my previous email or not, so forwarding it directly to you.<br>
<br>
Begin forwarded message:<br>
<br>
From: Brian Eng via dsg-hallb_gas <dsg-hallb_gas@jlab.org><br>
Subject: Re: [dsg-hallb_gas] AHDC gas control<br>
Date: January 15, 2025 at 1:28:10 PM EST<br>
To: Marc Mcmullen via dsg-hallb_gas <dsg-hallb_gas@jlab.org><br>
Reply-To: Brian Eng <beng@jlab.org><br>
<br>
Hi Whit,<br>
<br>
The control pressure is measured by the transmitter in psig, which is then converted to mbar in software. According to the manufacturer it has a fixed 14.7 psi (so ~1013.529 mbar) offset. If the set point is at 90 mbar it is really ~1103.529 mbar.<br>
<br>
The ambient pressure sensor readout that is being displayed got stuck, rebooting it got the values updating again. The EPICS PV that ALERT is using is B_SYS_WEATHER_FC_L1:Press2 in case you wanted to monitor it directly/separately.<br>
<br>
Let me know if there’s any other questions.<br>
<br>
Brian<br>
<br>
On Jan 15, 2025, at 12:34 PM, Marc Mcmullen via dsg-hallb_gas <dsg-hallb_gas@jlab.org> wrote:<br>
<br>
Hi Bob, I’m out sick. So I’m forwarding this tho the group. Brian can probably look into it.<br>
<br>
Also I looked and the input flow to MFC 308 is set to 20 sccm. Maybe change that to 167 sccm.<br>
<br>
Marc<br>
<br>
Get Outlook for iOS<<a href="https://urldefense.proofpoint.com/v2/url?u=https-3A__urldefense.us_v3_-5F-5Fhttps-3A__aka.ms_o0ukef-5F-5F-3B-21-21G-5FuCfscf7eWS-21cMG23h01E0cLmgFH7Y9odbg4EzjkBfFl9OZtr6hRBN15weKjK-2DA447CVEL2tI981ZqrTiVinSEmOzA-24&d=DwMGaQ&c=CJqEzB1piLOyyvZjb8YUQw&r=vRrieMgp4FbexQ5kgKImwA&m=4ivNaLHIEd-1YRwvzy3oMWNJI8Ue6XJZGH3uNE1qb4l1RnT5S_C-NQKl_g0KWprR&s=wAuBpR_1TE8UqMpR4nmS-vlDwbpou22SaUW-qbr4f0I&e=" id="OWAb0e7956d-08ea-a398-e57e-852a02b743e3" class="OWAAutoLink" data-auth="NotApplicable">https://urldefense.proofpoint.com/v2/url?u=https-3A__urldefense.us_v3_-5F-5Fhttps-3A__aka.ms_o0ukef-5F-5F-3B-21-21G-5FuCfscf7eWS-21cMG23h01E0cLmgFH7Y9odbg4EzjkBfFl9OZtr6hRBN15weKjK-2DA447CVEL2tI981ZqrTiVinSEmOzA-24&d=DwMGaQ&c=CJqEzB1piLOyyvZjb8YUQw&r=vRrieMgp4FbexQ5kgKImwA&m=4ivNaLHIEd-1YRwvzy3oMWNJI8Ue6XJZGH3uNE1qb4l1RnT5S_C-NQKl_g0KWprR&s=wAuBpR_1TE8UqMpR4nmS-vlDwbpou22SaUW-qbr4f0I&e=</a>><br>
________________________________<br>
From: Bob Miller <rmiller@jlab.org><br>
Sent: Wednesday, January 15, 2025 11:20 AM<br>
To: Armstrong, Whitney R. <warmstrong@anl.gov>; Marc Mcmullen <mcmullen@jlab.org><br>
Subject: Re: AHDC gas control<br>
<br>
Hi Whitney,<br>
<br>
I will refer this question to Marc, as he wrote the controls.<br>
<br>
<br>
<br>
Bob Miller<br>
Hall B Lead Engineer<br>
(757) 822-9586<br>
________________________________<br>
From: Armstrong, Whitney R. <warmstrong@anl.gov><br>
Sent: Wednesday, January 15, 2025 10:44 AM<br>
To: Bob Miller <rmiller@jlab.org><br>
Subject: [EXTERNAL] AHDC gas control<br>
<br>
Hi Bob,<br>
<br>
I have a question about the gas control system. When the alert gas set point is set to 90 mbar, what is that relative to in order to provide stable absolute pressure?<br>
<br>
Also, the ambient pressure readout appears to not change and is at a value of 1017.54.<br>
<br>
Thanks,<br>
Whit<br>
<br>
Whitney Armstrong<br>
Assistant Physicist<br>
Physics Division<br>
Building 203<br>
<br>
Argonne National Laboratory<br>
9700 S. Cass Ave. | Argonne, IL 60439<br>
630-252-5112 | 717-341-1080 mobile<br>
warmstrong@anl.gov<br>
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