NI DAQmx Devices

In MxTransIt, use the NI DAQmx Transform's Terminal Configuration property to configure Analog Input (AI) ports. RSE and NRSE configured channels use a common ground, while Differential channels use port0 and port8 as "+" and "-"

The default is Differential inputs, using 2 pins per port. Only ports 0-7 and 16-23 can be used simultaneously in a differential or pseudodifferential configuration. If you change the Analog Input port configuration to RSE or NRSE, then the corresponding port (negative port) shows up (offset by 8).

For example, if you change AI0 to NRSE or RSE, then AI8 shows. (So if you change all of them to NRSE/RSE, then all 32 channels show up.)

National Instruments specifies that the NI 6323 device has:

32 Single-Ended Channels or

16 Differential Channels

When working with counter ports, use the default NI-DAQmx Counter Pins as described in corresponding NI user manuals.

To measure angular position with angular encoders like quadrature encoders:

•Choose the NI board's input counter and corresponding NI Daqmx Transform output counter port.

•Connect the angular encoder's channels A, B and, if needed and available, channel Z to the appropriate default NI-DAQmx counter pins.

•Configure the NI DAQmx Transform output port choosing AngleMeasurement as the Port Sub Type and setting  the appropriate values for Position Decoding Method, Enable Channel Z, Z Phase, and Z Value, all of which are meaningful for AngleMeasurement only.

•Angular position is measured in ticks.

Note: Most likely it is possible to also measure linear position with the two-pulse encoder by setting the corresponding NI DAQmx Transform output counter port's Port Sub Type to AngleMeasurement and Position Decoding Method to TwoPulseCounting.

When an NI DAQ inport is selected the Properties window appears a shown below.

Set the properties for your configuration:

1.Analog Configuration: these properties only apply to analog ports

2.Counter Configuration: only applies to ctr ports

3.Misc: Frequency only applies to the ctr ports and is the base frequency of the PWM Signal for which you are trying to measure the duty cycle. PWM Starting edge also only applies to ctr ports. It is the edge of the signal that is used as a reference for the PWM measurement.

Use the Port Properties to set the frequency.  Select Properties >Counter Configuration>Frequency (Hz). To set the initial value of the duty cycle, select Properties>Signal Info>Signal Info> Initial Value.

The NI DAQs have outports (ctr0 through ctr3) that accept a number corresponding to a duty cycle (0 – 100); with 100 corresponding to the output always high and 0 always low. These ports map to the DAQ’s PFI Counter Out ports and pins as shown:

There are three types of DAQ outport properties:

Digital Outports:

Analog Configuration is not relevant.

Counter Configuration is not relevant

Analog Outports:

Analog outports produce an analog voltage corresponding to the port’s input. The values in Analog Configuration must not exceed the properties of the hardware.

Counter Configuration is not relevant.

Digital Configuration is not relevant.

CTR Outports:

The ctr ports produce a PWM signal at a rate set by the Frequency property of the Counter Configuration. The port’s input is a number between 0 and 100 corresponding to the duty cycle.

Analog Configuration is not relevant.

Digital Configuration is not relevant.

There are counters available in NI DAQ Transforms (Ctr0 to Ctr3), but they are sometimes unreliable.

NI DAQ has ports that output PWM signal which can be used for PWM Duty cycle percentage calculations.

MxSuite has an independent PWM counter (Pulse Measurement Transform) to perform this.

As per NI DAQ 6323 pin layout, below are the pins that must be used for PWM calculations:

Find complete manuals here:

•http://www.ni.com/pdf/manuals/370784j.pdf

•http://www.ni.com/pdf/manuals/374463b.pdf

The Harness in MxTransIt looks like this:

Direct DAQ ports can be used for plotting the PWM waveform itself. The Pulse Measurement outports provide the Duty Cycle percentage.

Note: Be sure the Measurement Window is a multiple of the period of the expected Signal.  If the frequency is known and if measurement is kept exact same as frequency, then there may be issues due to any tolerance issues.

For any signal that is 200 Hz(5ms signal time), the Measurement Window should be 10ms, 15ms, or higher multiples of 5ms.