USB-4432 Feature Usage

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Updated2023-02-20
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102.4 kS/s, 100 dB, 0.8 Hz AC/DC Coupled, 5-Input Sound and Vibration Device

5 analog input channels; ±40 V; 102.4 kS/s simultaneous sampling rate
24-bit resolution for good signal to noise ratio on AI channels
4 channels with software-selectable IEPE signal conditioning (0 or 2.1 mA; no IEPE on fifth channel)

USB-4432 Pinout

Front Panel

Back Panel

Table 1. Signal Descriptions
Signal	Reference	Description
AI <0..4>+, AI <0..4>-	—	Analog Input Channel—AI+ and AI- are the positive and negative inputs of the pseudodifferential analog channel.
PFI <0..7>	GND	Programmable Function Interface—A digital trigger input.
GND	—	Ground—Ground reference for the PFI inputs.

Table 2. LED State/Device Status
POWER	ACTIVE	Device Status
Off	Off	Device is not powered.
On	Off	Device is configured, but there is no activity over the bus.
On	On	Device is configured and there is activity over the bus.

Block Diagram

The following figure shows the USB-4432 block diagram.

Analog Input Features

The following figure shows the USB-4432 analog input circuitry block diagram.

The USB-4432 analog input channels feature the following:

Sampling rates up to 102.4 kS/s
Input voltage range of ±40 V pk
Per channel AC or DC coupling
Per channel selectable IEPE current excitation on channels 0..3
Overload detection
Anti-alias filtering
Multiple triggering modes, including external digital triggering

Note When there is no sensor or source connected to a channel configured in DC coupling, it will read approximately 2 V to 2.5 V.

Anti-Aliasing Filter Response

The following figure shows the digital filter input frequency response.

The following figures show the response of the analog input filters. Since the digital filter lets through narrow bands of frequencies at multiples of 64 fs, it is necessary to use the previous figure to know how much attenuation is received by signals in these bands.

For example, when sampling at 51.2 kS/s, the digital filter will remove any out-of-bandwidth tones up until a 51.2 kHz band centered on 64 f_s, or 3.2768 MHz ±25.6 kHz. If noise in the input signal falls into this narrow window, the noise is not rejected by the digital filter. In this limited frequency range, you must consider the analog filter. The analog filter on the USB-4431 has an attenuation of 62 dB at 3.2768 MHz. Therefore, the worst-case alias rejection is 62 dB in this example.

This situation represents the worst-case alias rejections for a sampling rate of 51.2 kS/s. You would only observe this worst-case scenario with a well-defined tone in a narrow frequency range. In real measurement situations, it is more likely that any energy passing the digital filter consists only of low-amplitude noise. If an unwanted component does appear in the digitized signal, increasing the sampling rate might provide an easy solution by both improving the rejection from the analog filter and by repositioning the digital filter so that it can eliminate the alias.