Questions about the DAQPad-6020(BNC)!

[sammi]

I am a newer in NI DAQPad-6020E(BNC) and also unfamiliar with such hardware device.We know that the board has 16/8 I/O from ACH0 to ACH15. In the deviec user manual, it has mentioned three different input modes—nonreferenced single-ended(NRSE) input, referenced single-ended (RSE) input, and
differential (DIFF) input. But now what confuses me is that where are the inputs ACH8 to ACH15 and how to connect a out equipment to a couple inputs such as the couple ACH0 and ACH8 in DIFF input mode. Are they just connected together to the ACH0 instead to ACH0 and ACH8 espectively? Or how to connect external sensors to any input from ACH8 to ACH15 when in single-ended input mode.

Another question is the sensor volatage parameter sel
ection according to the DAQ protection voltage. Referring to the device user manual, the protection voltage is Vcc+0.5. Then, what does the constant Vcc point to? Where can I find the specified value of the Vcc since the sensor I/O voltage is direct relative to the board protection value. Thus, what the value is? Is it the same in all E-series DAQPad? Or is it referred to somewhere different from different device.

I am urged for your help since the project is coming.

Very thankful for your hearted help.

[sammi]

Could someone help me?

Thanks!

[Philip_Courtois]

Hi Sammi,

The DAQPad-6020E (BNC) is designed for convenient measurement of up to eight differential channels using BNC connectors and cabling. In certain situations, however, it may be desirable to increase the channel count beyond eight. In this case, you must use one of the single-ended measurement modes (RSE or NRSE) with the DAQPad-6020E (BNC). Up to 16 (ch0 to ch15) single-ended channels are available in the single-ended measurement configuration.

Single-ended measurement modes require changing the source type switch (S0 through S7) settings. Figure C-1 in the User Manual shows the ground-referenced resistor switch settings.

Actually the BNC connectors on the front are connected to differential channel pairs, so the BNC called ACH0 is actually
connected to ACH0 and ACH8. Therefore, if you want to do single-ended measurements, each BNC connector is giving access to the "+" terminal of two channels (ACHx and ACHx+8). Depending on your choice of referencing, the ground point of the signal should be connected to the AISENSE (for NRSE) or AIGND (for RSE) pin.

There are different overvoltage protection specifications depending on the input type. The analog inputs (AI) are protected up to +/-35V when powered on (+/-25V when off). The Vcc value you is referring to the digital 5V, but the analog inputs are not referring to this value.

Hope this gets you started.

Philip C.
Applications Engineer
National Instruments