[SystemSafety] COTS display certification

[paul_e.bennett at topmail.co.uk]

On 29/07/2016 at 10:14 AM, "Peter Bishop" <pgb at adelard.com> wrote:
>
>Well I did say *in principle* (i.e. ignoring memory constraint 
>issues).
>
>The main point I was trying to make is that we need equivalent 
>levels of
>assurance for code and data. And assurance of data integrity needs 
>more
>coverage in standards.
>
>Peter B

I don't get too involved in the display end of the system as my main 
focus is much closer to the "controlled process".

Looking at the source for the data (in my case the sensors) I 
implement a number of sanity checks to ensure that:-
   *  The sensor is connected
   *  The sensor is operating correctly
   *  The data values are within the expected range
   *  The sensor interface is operating correctly
   *  Required Power supplies to the sensor are operating correctly
      and within permitted range.
   *  All checksums are correct and calculated correctly
   *  Communications between sensor interface and the control
       system it is part of are operating correctly and occurring in a 
       timely manner.

Most of what I deal with are continuous autonomous controllers 
that are tasked with keeping critical processes operating within 
defined limitation parameters. The control room HMI aspect (that is 
often left to others) provides a window on all the parameters via 
mimic screens. Often I am using multiple sensors on the same
process monitoring point so that I am not reliant on just one
sensor being perfect.

Ensuring that data integrity is maintained throughout the whole 
system should be of concern to all who design, operate and 
manage the facility the system is part of. It would be a great shame 
if, after I have made efforts to ensure the data source integrity is
as good as I can make it, the communication and analysis code
mangles it into an unreliable mess.

So, treating the data as a component for which you expect a level
of Data Integrity requires examination of the whole chain from its
initial generation, through to how it is handled, processed, 
communicated, delivered and used.

Regards

Paul E. Bennett IEng MIET
Systems Engineer

-- 
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Paul E. Bennett IEng MIET.....<email://Paul_E.Bennett@topmail.co.uk>
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