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© National Instruments Corporation A-1 Lab-NB User Manual
Appendix A
Specifications
This appendix lists the specifications of the Lab-NB. These specifications are typical at 25° C unless otherwise
stated. The operating temperature range is 0° to 70° C.
Analog Input
Number of input channels........................................................8 single-ended
Analog resolution........................................................................12 bits, one part in 4,096
Relative accuracy (nonlinearity)...........................................±1.5 LSB max,
(nonlinearity + quantization error;...............................±1.0 LSB typ
see explanation of specifications)
Differential nonlinearity...........................................................±1.0 LSB max (no missing codes),
±0.5 LSB typ
Analog input range.....................................................................±5 V or 0 to +10 V; jumper-selectable
Input signal gain..........................................................................1, 2, 5, 10, 20, 50, 100; software-selectable
Measurement (gain) accuracy
gain = 1..................................................................................±0.04% max,
±0.025% typ
Offset error
(calibration performed at gain = 1)
gain ≤ 20................................................................................±4 LSB max, ±2 LSB typ
gain > 20................................................................................±20 LSB max, ±10 LSB typ
Offset adjustment range, min
(unipolar or bipolar ranges)............................................±47 LSB
Gain adjustment range, min
(unipolar or bipolar ranges)............................................±31 LSB
System noise.................................................................................0.3 LSB rms for gain = 1
0.6 LSB rms for gain = 100
Temperature coefficients
Gain error..............................................................................±10 ppm/°C
Offset error...........................................................................450 µV/°C + 10 µV/°C
*
gain
Input bias current........................................................................150 pA
Input impedance..........................................................................0.1 GΩ in parallel with 45 pF
Input protection............................................................................±45 V on all inputs (not ground)
Explanation of Analog Input Specifications
Relative accuracy is a measure of the linearity of an ADC. However, relative accuracy is a tighter specification than
a nonlinearity specification. Relative accuracy indicates the maximum deviation from a straight line for the analog-
input-to-digital-output transfer curve. If an ADC has been calibrated perfectly, then this straight line is the ideal
transfer function, and the relative accuracy specification indicates the worst deviation from the ideal that the ADC
permits.
A relative accuracy specification of ±1 LSB is roughly equivalent to (but not the same as) a ±
1
/2 LSB nonlinearity
or integral nonlinearity specification because relative accuracy encompasses both nonlinearity and variable
quantization uncertainty, a quantity often mistakenly assumed to be exactly ±
1
/2 LSB. Although quantization
uncertainty is ideally ±
1
/2 LSB, it can be different for each possible digital code and is actually the analog width of
each code. Thus, it is more specific to use relative accuracy as a measure of linearity than it is to use what is