The Model D4 Data Acquisition Conditioner is a portable, USB-powered precision instrument for use with resistive strain gages and strain gage-based transducers. The Model D4 has four channels of data acquisition. Connection to each channel is via a RJ-45 connector. Each channel of input accepts either full-, half-, and quarter-bridge configuration. All required bridge completion components for 120-, 350-, and 1000-ohm bridges are supplied. Operation of the Model D4 is performed with commands sent via the USB connection. User-friendly application software is provided to control the D4 with a MS Windows-based personal computer. The software connects with up to six D4 units to create a system of up to 24 channels. The D4 units can be connected directly to a computer through its USB ports or through a USB hub. A Programmer’s Reference Kit that includes a Programmer’s Reference Manual, a NI LabVIEW instrument driver, and programming examples to simplify writing custom applications is also included. The D4 is also supplied with a calibration software utility that allows calibration of the D4 via the USB interface. The application software, Programmer’s Reference Kit, and Instruction Manual are on a single CD included with the D4 unit. The Model D4 uses modern digital signal processing technology to provide excellent noise rejection and stability. Proprietary scaling and linearization algorithms provide unsurpassed measurement accuracy for strain gage bridge measurements.