C Series Physical Channels

In physical channel names, cDAQ1Mod1 is the default device name for a C Series device plugged into an NI cDAQ-9172 chassis, where cDAQ1 is the default chassis device name, and Mod1 refers to the slot number. You can change these names in MAX.

Analog Input

The NI 9225 has three physical channels named cDAQ1Mod1/ai0 to cDAQ1Mod1/ai2. The NI 9211, NI 9215, NI 9217, NI 9219, NI 9229, NI 9233, NI 9234, NI 9237, and NI 9239 have four analog input physical channels named cDAQ1Mod1/ai0 to cDAQ1Mod1/ai3. The NI 9201, NI 9203, NI 9221, NI 9235, and NI 9236 have eight analog input physical channels named cDAQ1Mod1/ai0 to cDAQ1Mod1/ai7.

The NI 9205 and NI 9206 have 32 analog input channels named cDAQ1Mod1/ai0 to cDAQ1Mod1/ai31. You can configure channels 0-7 and 16-23 as the positive channel of a differential pair. If N is this channel, channel N + 8 is the negative input of the pair. For instance, if you configure channel 1 in differential mode, the positive input is channel 1, and channel 9 is the negative input. Use only the physical channel name of the positive channel (not both) when creating a differential channel.

You can use channels from multiple analog input C Series devices in the same DAQmx task. Only one analog input task per chassis can run at a given time.

Strain and Wheatstone Bridge Measurements

The NI 9235, NI 9236, and NI 9237 support only the AI Strain Gage and AI Custom Voltage With Excitation channel types.

When using the NI 9219, NI 9235, NI 9236, or NI 9237 with an AI Custom Voltage With Excitation channel, you must set the AI.Excit.UseForScaling attribute/property to true. This attribute/property causes the channel to return ratiometric data: Vin/Vex. The NI 9219, NI 9235, NI 9236, and NI 9237 modules perform this division in hardware.

For the NI 9219, NI-DAQmx requires the AI.Excit.Val attribute/property to be set to 2.5 V for AI Strain Gage and AI Custom Voltage With Excitation channel types and to 500 µA for resistance and RTD measurements. The actual excitation voltage or current output by the NI 9219 varies with the sensor resistance or the load being measured.

With the NI 9219, NI 9235, NI 9236, and NI 9237, the AI.Bridge.InitialVoltage attribute/property refers to a voltage, not a ratio, so it should be set to the ratio Vin/Vex returned by the device multiplied by Vex.

The NI 9219 does not have quarter bridge completion circuitry, which affects AI Strain Gage Quarter Bridge I channels and AI Custom Voltage With Excitation Quarter Bridge channels (but not AI Strain Gage Quarter Bridge II channels). With these channels, the NI 9219 performs a 2-wire resistance measurement on the active gage element, then NI-DAQmx uses software scaling to convert the resistance measurement into a bridge ratio. For these channels, the polynomial coefficients specified by the AI.DevScalingCoeff attribute/property convert unscaled data into Ohms, not into V/V. Likewise, the AI.Rng.High/AI.Rng.Low attributes/properties should be specified in units of Ohms, not V/V.

When the NI 9219 is in quarter bridge mode, you need to use the AI.Bridge.NomResistance attribute/property to control whether the channel uses the 120 Ω range or the 350 Ω range.

Analog Output

The NI 9263 and NI 9265 have has four analog output physical channels named cDAQ1Mod1/ao0 to cDAQ1Mod1/ao3. The NI 9264 has sixteen analog output physical channels named cDAQ1Mod1/ao0 to cDAQ1Mod1/ao15.

You can use channels from multiple analog output C Series devices in the same analog output task. If the task is hardware-timed, there is a limit of 16 channels per task, but if the task is software-timed, the number of channels is limited only by the number of devices. Only one hardware-timed analog output task per chassis can run at a given time.

When using the the NI 9263, NI 9264, or NI 9265, you can run only one type of timing at a time. You can have one software-timed task per channel or one hardware-timed task running on a device at one time, but you cannot have a combination of timing on that device. For instance, you can run up to four software-timed tasks on an the NI 9265 concurrently, but running one hardware-timed task with one software-timed task generates an error.

Digital Input and Output

The NI 9402, NI 9435, and 9481 have four lines of digital input and/or output named cDAQ1Mod1/port0/line0 to cDAQ1Mod1/port0/line3. The NI 9411 has six lines of digital input named cDAQ1Mod1/port0/line0 to cDAQ1Mod1/port0/line5. The NI 9401, NI 9421, NI 9422, NI 9423, NI 9472, NI 9474, and NI 9485 have eight lines of digital input and/or output named cDAQ1Mod1/port0/line0 to cDAQ1Mod1/port0/line7. These lines belong to a single port, and the physical channel cDAQ1Mod1/port0 refers to all four, six, or eight lines at once.

In the NI cDAQ-9172, C Series devices in slots 1, 2, 3, and 4 can perform both hardware-timed and static digital operations. You can use devices in slots 5 and 6 as static digital I/O lines or PFI lines, /cDAQ1Mod5/PFI0 to /cDAQ1Mod5/PFI7 and /cDAQ1Mod6/PFI0 to /cDAQ1Mod6/PFI7. Devices in slots 7 and 8 can be used only as static digital I/O lines. Hardware-timed digital input/output and PFI lines are only supported on correlated digital I/O modules. Refer to Digital I/O Considerations for C Series for more information.

Counter Input and Output

The NI cDAQ-9172 has two counter/timers that are used with a C Series digital I/O device in slot 5 or 6. These are referred to by the physical channel names cDAQ1Mod5/ctr0, cDAQ1Mod5/ctr1, cDAQ1Mod6/ctr0, and cDAQ1Mod6/ctr1. Unlike the other I/O types, these physical channel names do not refer to terminals on the device I/O connector but instead to circuits within the chassis. The NI cDAQ-9172 chassis also has a 4-bit frequency output generator, referred to as cDAQ1Mod5/freqout and cDAQ1Mod6/freqout.

Each counter has four primary terminals associated with it. These are the terminals used as the SOURCE, GATE, AUX, and OUT functions. NI-DAQmx has default values for these terminals. For counter input tasks, if you know whether your signal provides the SOURCE, AUX, or GATE function and wire your signal to the default, you do not have to set the Input Terminal attribute/property.

Counter/timers are only supported on correlated digital I/O modules. Refer to Digital I/O Considerations for C Series for more information.

The following table shows the counter terminal defaults for 8-channel DIO/DI/DO C Series devices.

The following table shows the counter terminal defaults for 6-channel DIO/DI/DO C Series devices.

The following table shows the counter terminal defaults for 4-channel DIO/DI/DO C Series devices.

Refer to C Series Signal Connections for Counters for more information.