The Model 401 is a complete, high-resolution Delta-Sigma data acquisition system
with a TCP/IP interface. It uses an extremely capable micro controller with substantial
RAM and program memory available. This processing power will allow future versions to have
greatly extended functionality. The battery-backed RAM and non-volatile flash memory available
will make stand-alone data acquisition practical for many applications. The connector
pinout is identical to the Model 301 and the programming interface is very similar. That
makes it easy to support both USB and TCP/IP from the same application.
Lawson Labs has been designing and building high-resolution Delta-Sigma Data Acquisition Systems
since 1991. The Model 401 represents our seventh generation of Delta-Sigma design. It incorporates
the electrical 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. Both 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 401 operates from a single unregulated power supply.
Drivers are provided for Win98 through Win10, with VisualBasic and VisualC++ sample application code. Multiple A/Ds
can be added using inexpensive 10Base-T Ethernet hubs. Units can be dynamically connected or disconnected
without interrupting other ongoing acquisition.
SPECIFICATIONS
A/D TYPE
24-bit delta-sigma converter with
microcontroller supervisor and
electrical isolation.
MONOTONICITY
23 bits
LINEARITY
+/-0.002% of full scale.
DIFFERENTIAL INPUT RANGE
+/-5 volts
DC COMMON MODE RANGE
+/-6.5 volts
DC COMMON MODE REJECTION
-100 dB typical
ANALOG INPUTS
2, multiplexed true differential
protected to +/-60 volts.
INPUT IMPEDANCE
1013 ohms typical
PROGRAMMABLE DATA RATE
10 to 1000 Hz, lower rates are
generated through digital averaging.
EFFECTIVE RESOLUTION
Effective resolution is defined as total
resolution in bits minus RMS noise in
bits.
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. A digital input is added into the data stream after each conversion.
That feature allows maximum timing accuracy for digital events.
DIGITAL INPUTS
8 bits, contact closure or 5 volt logic compatible.
