Hi All
After many years of battling with serial devices in a noisy environment
I now tend towards devices which have an option for enabling a protocol
and/or a checksum or CRC. Doing that allows detecting and tossing bad
data, which is not feasible with pure ASCII devices. We have some
devices at the Keck observatory that occasionally get reprogrammed
simply from single bit changes in the data stream (distance is many
hundreds of feet and communications must pass through slip rings, which
are brushes dragging across copper strips)!
I do not know if the Keithley units have such features but...
AH
-----Original Message-----
From: Mark Rivers [mailto:[email protected]]
Sent: Thursday, February 02, 2006 10:48 AM
To: Josh Stein
Cc: TechTalk EPICS
Subject: RE: Cost effective solution for monitoring a large number of
temperatures
Hi Josh,
I don't have hard numbers for the 2700. On the older 2000 with a 10
channel card we can get a little faster than 1Hz if all 10 channels are
active I think (=10 readings per second). They are mechanical switches
for selecting the active input.
Mark
-----Original Message-----
From: Josh Stein [mailto:[email protected]]
Sent: Thursday, February 02, 2006 2:16 PM
To: Mark Rivers
Cc: TechTalk EPICS
Subject: Re: Cost effective solution for monitoring a large
number of temperatures
Hey Mark,
The Keithly 2700 looks like the ticket. The other solutions
may be a
bit more 'techy' but I'm aiming for COTS as much as possible. It also
appears that Keithly is offering an 40 channel module with
cold junction
compensation now - I'll look into that one. What rates are
you able to
scan this beast at? I imagine it is hardware bound.
Thanks,
<josh>
Mark Rivers wrote:
Hi Josh,
In synApps we support the Keithley 2700. Each of those
units takes 2 cards for a total of 40 thermocouples. It
costs about $2K, so $50 per thermocouple. It can be extended
with external multiplexors, but EPICS support would need to
be written for those.
Mark
________________________________
From: Josh Stein [mailto:[email protected]]
Sent: Thu 1/19/2006 9:03 AM
To: TechTalk EPICS
Subject: Cost effective solution for monitoring a large
number of temperatures
Controls experts,
In the undulator hall of the LCLS we expect to monitor (what I
consider) a large number of temperature points (on the order of about
300). My past experience with thermocouples has been local
installations
of between one and eight data points. It would be easy to just scale
that solution by a factor of 40, but I have to believe there are more
cost effective solutions.
Can anyone with experience in this regard please point me
in the right
direction? I'm looking for hardware that is, of course,
EPICS compliant.
Thanks,
<josh>
