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Appendix A Specifications
PC-LPM-16/PnP User Manual A-4
National Instruments Corporation
Bus Interface
Type.................................................... Slave
Power Requirement
+5 VDC (
±
10%).................................. 50 mA typ
+12 VDC (
±
5%).................................. 15 mA typ
-12 VDC (
±
5%) .................................. 15 mA typ
Note:
These numbers do not include an additional 1 A from the 5 V power supply.
The 50-pin I/O connector can draw 0.5 A from the +12 V supply.
Physical
Dimensions......................................... 11.0 by 9.9 cm (4.4 by 3.9 in.)
I/O connector...................................... 50-pin D male ribbon cable
connector
Environment
Operating temperature......................... 0
°
to 70
°
C
Storage temperature ............................ -55
°
to 150
°
C
Relative humidity................................ 5% to 90% noncondensing
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 a
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
normally called nonlinearity, because relative accuracy ensures that the
a.Book : I.Appendix A Page 4 Wednesday, November 20, 1996 6:36 PM