teststand Advanced AI Single Scan buffered

[trout00]

I have teststand 2.1f1 and labview 6.1
in MAX 2.2 I set up my virtual channel
Hardware: PCI 6036 with SCXI and a module for load cells
When I use the Advanced AI Single Scan to read the virtual channel, the first reading is the previous load I applied to the load cell. I don't know why. Do I need to configure something in TESTSTAND-SETUP Tab?
I already configure my virtual channel in MAX 2.2
This behavior did not happen if I just Labview 6.1 (no TestStand involved)
example: if I put 5lbs on the load cell and read the virtual channel 3 times,
1st reading is 0
2nd reading is 5
3rd reading is 5
now if I remove the force, and read the channel 3 times
1st readign is 5
2nd reading is 0
3rd reading is 0

[Alejandro_del_Castillo]

Are you configuring a buffered or non-buffered acquisition?

The AI Single Scan vi returns one data point directly from the analog channel of the board on a non-buffered acquisition. In a buffered acquisition, it returns one point from the buffer, and this point might not be the latest one. In case you are using a buffered acquisition you can try to set the terminal opcode to "read newest value" to make sure you are always taking the latest value on each read.

Best Regards,

Alejandro del Castillo
NI

[trout00]

How do I know whether I am using a buffered or a non-buffered acquisition?

[markp01]

Hi trout00,

You need to look how the AI Config.vi is setup.
If the "allocation mode" control is set to 'deallocate memory' (1) then you are using non-buffered.

regards
Ray Farmer

[Alejandro_del_Castillo]

If your buffer size in AI Config is equal to 0 then you are having a non buffered acquisition. In the case of a buffered acquisition you will have also AI Start, since this vi is the one in charge of setting a sampling rate. In a buffered acquisition the board will be filling a buffer in memory automatically at the specified rate and Ai Single Scan will be taking one sample at a time from that buffer. In a non-buffered acquisition, Ai Single Scan will be taking one sample when the vi is called. No acquisition on the background will be active.

Alejandro del Castillo
Ni