6225 questions

[JaneGuo]

1. Low-pass filter for PCI6225Is the low-pass filter for PCI6225 configurable or fixed?The User Manual for 622x states the following:  If the programmable filter is not enabled, the cutoff frequency is fixed at 750 kHz. If the cutoff is programmable, choose the lower cutoff to reduce measurement noise. (Page 52, section 4-4) However the spec for 6225 states that Small signal bandwidth (–3 dB)......700 kHz Please help confirm which one is correct. 2. AI Ground-Reference Setting for PCI6225In the User Manual for 622x, page 55, figure 4-3 gives an example where channels in the same device are configured with different AI Ground-Reference setting.In Figure 4-3, channel 0 is configured in differential mode, and channel 1 is configured in RSE mode. 

I though the setting was global for device, which means that I could configure the board as either differential input or RSE/NRSE input type. Now the figure quoted seems to suggest that it’s possible to configure the channels in the same board as different type.

[JaneGuo]

Sorry the format of previous message is confusing. Here is it again:

1. Low-pass filter for PCI6225Is the low-pass filter for PCI6225 configurable or fixed?The User Manual for 622x states the following:  

If the programmable filter is not enabled, the cutoff frequency is fixed at 750 kHz. If the cutoff is programmable, choose the lower cutoff to reduce measurement noise. (Page 52, section 4-4) 

However the spec for 6225 states that

Small signal bandwidth (–3 dB)......700 kHz 

Please help confirm which one is correct. 

2. AI Ground-Reference Setting for PCI6225In the User Manual for 622x, page 55, figure 4-3 gives an example where channels in the same device are configured with different AI Ground-Reference setting.

In Figure 4-3, channel 0 is configured in differential mode, and channel 1 is configured in RSE mode. 

I thought the setting was global for device, which means that I could configure the board as either differential input or RSE/NRSE input type. Now the figure quoted seems to suggest that it’s possible to configure the channels in the same board as different type. Is it possible?

[stilly32]

Hello,

Glad to see you've already done some reading on the Manual. The 622x devices do not support a programmable filter on the AI. If it did it would list the filter cut-off like in the specfications of the 628x devices (which do support a programmable filter). 

You can configure each channel to have a different ground reference, so you could read AI 0 differentially, ai 1 RSE and ai2 NRSE in the same task for example.  If you set up a task in MAX with multiple channels you can see that each can be setup with a different configuration (as long as the channel supports it).

Hope this helps,

Andrew S