OVERVIEW

The Model 302 is a complete, Delta-Sigma high-resolution data acquisition system for the Universal Serial Bus (USB). It serves as a general purpose A/D converter or as a built-in interface for a wide variety of instrumentation. Up to 32 Model 302s can be connected to a single USB port using inexpensive hubs. Six analog input channels are provided, along with three analog outputs, four digital inputs and eight digital outputs.

Lawson Labs has been designing and building high-resolution Delta-Sigma Data Acquisition Systems since 1991. The Model 302 represents our sixth generation of Delta-Sigma design. It incorporates the optical isolation and input protection that have long allowed our high resolution systems to function reliably in the industrial environment.

The standard analog input range is +/- 5 volts, true differential. The maximum single-channel data rate is 1000 Hz at 20 bits effective resolution. Two channels can be scanned at 100 Hz with effective resolution of 20 bits. As the unit is slowed down, it quickly gains effective bits to 22 bits at 200 Hz and 22.5 at 50 Hz for single-channel operation. The input impedance is 1013 ohms and the DC common mode rejection is typically -100 dB. The isolated portion of the Model 302 operates from a single unregulated, low-power supply.

Drivers are provided for Win98 through Win10, with sample application code for VisualBasic, VisualC++, .NET (VisualBasic, VisualC++, VisualC#) and LabView®. The VB sample code includes a real-time graphic presentation of data, and is powerful enough for many general-purpose data logging applications. Multiple Model 302s can be split between 32 applications, or all used by one, or anything in between. Units can be connected or disconnected on the fly, without interrupting other ongoing acquisition. In order to obtain fully independent operation, even under fault conditions, we found it beneficial to write our own low level USB device drivers. These signed drivers provide high-reliability operation for critical acquisition tasks.

Each Lawson Labs USB data system is programmed with a unique ID number to eliminate ambiguity when multiple data systems are connected. The unique ID also provides the additional benefit that ID numbers can be used for software protection. We can reserve a range of ID numbers for a particular customer. Application software can then verify the ID number to guarantee that the software installation is authorized.




SPECIFICATIONS

A/D TYPE
24-bit delta-sigma converter with microcontroller supervisor and optical isolation

MONOTONICITY
23 bits

LINEARITY
+/-0.002% of full scale

DIFFERENTIAL INPUT RANGE
+/-5 volts standard
+/-2, +/-1, +1/-0.4v available

DC COMMON MODE RANGE
+/-6.5 volts

DC COMMON MODE REJECTION
-100 dB typical

DIFFERENTIAL ANALOG INPUT CHANNELS
6 Multiplexed true differential protected to +/-60 volts

ANALOG OUTPUTS
3 at 14-bit resolution, settling to 99% of full scale in 1 second

First output 0-5 volts. Other outputs selectable, 0-5 or +/-5volts

INPUT IMPEDANCE
1013 ohms typical

PROGRAMMABLE DATA RATE
50 to 1000 Hz, lower rates are generated through digital averaging

EFFECTIVE RESOLUTION
The effective resolution is defined as total resolution in bits minus RMS noise in bits. The figures below use an oversampling ratio of four.
Rate
Effective Resolution in Bits
1000
20
500
21
200
22
50
22.5


SCANNING MODE
Three scan types are available, single channel, multi-channel, and a calibration scan that adds a reading of the zero channel at the end of each scan for offset drift compensation. The max number of data points per second in multi-channel scanning mode is 200. Any of the three scan types can add a digital input into the data stream after each conversion. That feature allows maximum timing accuracy for digital events.

DIGITAL INPUTS
4 contact closure or 5 volt logic compatible

DIGITAL OUTPUTS
8 latched, ruggedized, double-buffered 5V outputs

POWER REQUIREMENT
11 to 15 VDC, regulated or unregulated, for isolated circuitry or 15 to 30 VDC with pre-regulator option

TYPICAL POWER CONSUMPTION
The microcontroller operates as a low-power USB bus-powered device. The analog input and digital I/O requires 25 MA (add drive current for active digital outputs, up to 20 MA each).

SIZE
6.5 x 4.8 x 0.8 inches

OPTIONS

options for power & USB connector placement  
click here, or image to zoom

expandable version  
see  M302EXPv1  expansion board

bulkhead mount cable option  

custom USB connector placement  

The Model 302 can be fitted in the EMF6 einclosure.
Contact Factory for details.

CONNECTORS
All input and output (except USB) is via screw terminals on 0.2 inch centers

PRICE
$450.00 including wall-mount power supply.



   
Contact us for sales or technical assistance  
lawsnlab@lawsonlabs.com

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