What's the max sampling rate of the system which use SCXI-1102B, with PXI-6289?

[Anooptk]

Hi all,

I'm using a PXI-6289 M series Daq in 1052 Chassis. Input modules are SCXI-1102B with SCXI-1303 terminal blocks.

My question is, what is the maximum sampling rate i can achieve for a single channel? Does Input modules do any type of sampling or is the limit of DAQ device is the only limiting factor? ie; With the above configuration, is a sampling rate of 500kS/s achievable with input connected to SCXI module?

Second question is; SCXI 1102 has two selectable gains of 1 and 100, what is the advantage of having this gain when DAQ device itself can do this amplification? And how can I select this gain mode when I program in LV-2010?

Thanks,

Anoop.

[Brad_K]

Hi Anoop,

If there is only one channel in the task, then the SCXI-1102 does not limit the sample rate. Note that if you have CJC Source set to Built In, then SC1Mod1/_cjtemp is automatically added to the task, so the task really has two channels. If you try to exceed the sample rate limits of the SCXI module, you should get an error, if I remember correctly.

(Note: SCXI modules that support simultaneous sample and hold, such the SCXI-1140 or SCXI-1520, do limit the sample rate of a single-channel task unless AI.SampAndHold.Enable is set to false. This is because the SSH circuit requires time to track the input signal, as well as time to settle when switching to hold mode.)

Amplifying the signal in the SCXI module reduces the effect of noise picked up by cabling and chassis backplanes. This is even more important when using multiple daisy-chained chassis.

DAQmx automatically sets the SCXI gain and the DAQ device range based on the DAQmx Channel >> AI.Max and AI.Min properties. If you're using an AI thermocouple channel, DAQmx should already be setting the SCXI gain to 100. If you want to verify that the SCXI gain and DAQ device range settings are what you expect them to be, you can read the DAQmx Channel >> AI.Gain, AI.Rng.High, and AI.Rng.Low properties.

Brad

[SKant]

Hi,

 I want to read 4-20mA current using SCXI-1102B. We can use same card or not?

[Brad_K]

Hi aniba solutions,

You can measure current by adding shunt resistors. The SCXI-1308 terminal block works with the SCXI-1102B and has the correct value of shunt resistor to measure 4-20 mA.

Brad