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Entry  23 Sep 2019, Frederik Wauters, Suggestion, recover daq and hardware safety. 
    Reply  27 Sep 2019, Konstantin Olchanski, Suggestion, recover daq and hardware safety. 
       Reply  28 Sep 2019, Frederik Wauters, Suggestion, recover daq and hardware safety. 
          Reply  29 Sep 2019, Konstantin Olchanski, Suggestion, recover daq and hardware safety. 
             Reply  15 Oct 2019, Stefan Ritt, Suggestion, recover daq and hardware safety. 
Message ID: 1712     Entry time: 28 Sep 2019     In reply to: 1708     Reply to this: 1715
Author: Frederik Wauters 
Topic: Suggestion 
Subject: recover daq and hardware safety. 
Dear Konstantin,

So let me retract the term "safety issue" then, it was more a request/question for this type of 
info between the fe and the odb.

We have most of what you mention:
* The HV hardware has current limits
* The Hardware has fixed ramping limits.

same for the software. 

The issue occurs when e.g. one channel can not be turned on and ramp for some temp/specific 
reason, and someone else is working on the daq and reloads the odb for e.g. 1h ago.  

> > We have encountered a safety issue with our HPGe HV and it's midas frontend.
> At TRIUMF and other labs the words "safety issue" have very specific meaning and
> we tend to follow this guidance: MIDAS is not certified for and is not intended for use with 
> safety critical applications as defined here:
> > A safety-critical system ... malfunction may result in ... following outcomes:
> > death or serious injury to people
> > loss or severe damage to equipment/property
> > environmental harm
> If this is your case, you should use properly certified software *and hardware*. Safety 
> officers at most institutions require certified hardware interlocks and other protections to 
> prevent such undesirable outcomes. Use of certified PLCs is sometimes permitted.
> But I suspect in your case, there is no "safety issue", you only want to protect some 
> valuable but not critical equipment against accidental damage.
> In this case, you can probably use midas, but if midas malfunction may result in destroying 
> your experiment (i.e. accidentally set wrong voltage on 3000 phototubes), you should also 
> have hardware based protections (hardware limits on max/min high voltage). Most HV 
> power supplies implement such protections (screw-driver actuated max voltage limits).
> If there is danger of destroying your experiment you should also have an independent 
> review of your control system to avoid avoidable mistakes and obvious problems.
> > Turning off or changing HV unknowingly has to be avoided at all costs
> The function of changing high-voltage is implemented in your frontend program. Right in 
> the place in this program where you transmit the voltage setting from ODB to the hardware 
> is where you implement your protections (validate the voltage range, check that changing 
> the voltage is permitted, etc). This protects you against unexpected/incorrect/erroneous
> changes in ODB (wrong ODB is loaded, wrong values in ODB, ODB is corrupted, etc).
> In addition, it is wise to set software based limits in the HV power supply (software 
> controlled max high voltage, software controlled max current, etc). Most HV power supplies 
> implement such functions.
> To ensure high voltage cannot be changed at the wrong times, you can also implement 
> procedural and hardware protections, such as unplug the power supply control connection 
> (usually ethernet or serial or usb cable). This will prevent you from monitoring the high 
> voltage currents and the only solution is to use a  power supply with a hardware "write 
> protect" function (a key needs to be inserted and turned to allow changing anything).
> All of this is generic and applies to any controls software, not just MIDAS.
> Without at least some of these protections (especially protections in your frontend 
> program), the questions you asked about loading ODB are insufficient.
> K.O.
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