Sampling Two tasks on SCXI-1102 at different rates

[steorn]

Hi,

I have a 28 K-Type ThermoCouple Analog Inputs and 4 Voltage Analog inputs connected to a SCXI-1303 Terminal Block, which in turn is connected to a SCXI-1102 Thermocouple Amplifier in a SCXI-1000DC Chassis.

The SCXI-1000DC Chassis is connected to a PXI-6259 DAQ Card in a PXI Chassis, which in turn is connected to my PC.

I want to sample the 28 ThermoCouple input channels at one frequency (f1) whilst sampling the 4 Voltage input channels at another frequency (f2).

My only problem is how to use the sampling clocks?

Currently, i'm using the OnboardClock to continuously sample the 28 ThermoCouple input channels. However, when I try to use the OnboardClock to continuously sample the 4 Voltage input channels I understandably get a "resource in use" error (-50103). 

So what clock should I specify in order to also sample the 4 Voltage input channels ? I'm looking to have these tasks synchronised which is why I would love to use the same or similar clock.

NOTE: f1 is about twice per minute (0.033Hz) whilst f2 is about ten times per second (10Hz).

Any help here would be greatly appeciated. I have read quite abit on clock routing but surely there is an easier solution ?

Many thanks in advance for your due care.

Shaun.

[steorn]

Sorry...but i feel I should add that the SCXI-1102 multiplexes all 32 channels to one Analog Input channel on the PXI-6259 and I think this is why sample clock sharing is not going to work.

If my resoning is correct, an alternative solution would be to connect a standard SCB-68 to the second connector on the PXI-6259 (channels 16 to 31 inclusive) and then connect the Voltage analog input channels to that. 

That still begs the questions of which sample clock should I use for them though.

Again, any clarity here would be greatly appreciated.

Thanks.

[steorn]

bump...

[steorn]

This is painfull 😞

The SCXI-1102 multiplexes all 32 channels into 1 channel on the PXI-6259 DAQ card. This would lead one to believe that the remaining 31 channels on the PXI-6259 are available for use......alas it appears not. 

So gentlemen, how would you suggest I acquire 28 Analog ThermoCouple inputs and 4 Analog Voltage inputs using the kit described in my first post?

Many thanks in advance in the vain hope that someone might reply.

Cheers.

[Wolfgang]

I can't assist directly and only suggest to post it in a more appropriate forum, such as Multifunction DAQ

Wolfgang

[Mark_SAI]

Hi,

l would sample all the channels at 10hz, and discard 299 samples out of every 300 samples of your thermocouple channels. Your M-series DAQ card only has 1 ADC on board that is multiplexed among all the inputs (in this case, you are using the multiplexer on the SCXI module instead of the one onboard the M-series card) so its easier to keep this at 1 sample rate for all channels.

[phanisrikanth]

Hi,

My RT Data Acquisition System setup consist: PXI-8106  with three PXI-6254 modules(M-series), SCXI-1001 with four SCXI-1125 modules

Max Sampling Rate:10K

when I configure all the channels (count:64, both PXI and SCXI channels) and acquiring, I am observing a seven seconds delay of signal updating.for the 7 sec's time... graph is showing old data. which should not happen.

For example: 5V signal is applied, in software I can see that only after 7secs.

Note;For individual channel and few channels s/w updating has no problem.

As other DAS's are acquiring(updating) fine for the same signal.

->will this problem occurs with SCXI modules.

Please clarify my doubt

Thank you for any help in advance,

srikanth