Re: Power Supply Record?

[Luedeke Andreas <andreas.luedeke@psi.ch>]

Susanna Jacobson wrote:
> [...] we are considering writing a custom Power Supply record.  [...]
> I would also welcome any advice or cautions you have, based on your 
> experience in this area. [...]
Hi Susanna,
I had a similar idea 8 years ago for some in-house developed power 
supply at PSI.
Luckily I got some advice not to do it that way (Thanks Bob!).

If you use one record per power supply, your application will suffer 
from a lack of expandability, flexibility and usability.

Just some simple example:

Expandability:
My specification at the beginning consisted of about a dozen values for 
one power supply.
Within one year this did grow by a factor of 10.
I would rather have a template with 120 records connected to one power 
supply, then having a record with 120 fields.

Flexibility:
If you want to read a new value-type (e.g. resistance) from your PS, and 
let's say you have a serial connection to your PS.
Reading the new value should be possible by just adding a few lines in 
your protocol file and adding an "ai" record.
But if you have to add a field to a record it becomes much more trouble.

Usability:
you will read back a current and a voltage from the power supply.
Is HOPR/LOPR the display range for the current or the voltage?
Of course you can have an IHOP/ILOP and VHOP/VLOP, but since there is 
just one function get_graphic_double, no standard display will be able 
to use those fields context sensitive.
The same applies to ADEL, MDEL, HIGH, HIHI, LOW, LOLO, ....


Other people may disagree, but I would strongly advice you not to 
develop a power supply record.
Good luck with your power supplies anyway ;-)

Cheers
Andreas

--
Dr. Andreas Luedeke, SLS Operations Manager, Tel:+41-56-3104002
Andreas.Luedeke@psi.ch, http://people.web.psi.ch/luedeke