Measurement Computing USB-1208FS - Manual (Page 20)

20
Chapter 4
Specifications
All specifications are subject to change without notice.
Typical for 25°C unless otherwise specified.
Specifications in italic text are guaranteed by design.
Analog input
Table 1. Analog input specifications
Parameter Conditions Specification
A/D converter type Successive approximation type
Input voltage range for linear operation,
single-ended mode CHx to GND ±10 volts (V) max
Input common-mode voltage range for
linear operation, differential mode CHx to GND –10 V min, +20 V max
Absolute maximum input voltage CHx to GND ±28 V max
Input impedance 122 k
Ω
Input current (Note 1) Vin = +10 V 70 µA typ
Vin = 0 V –12 µA typ
Vin = –10 V –94 µA typ
Number of channels Software-selectable 8 single-ended / 4 differential
Input ranges, single-ended mode ±10 V, G=2
Input ranges, differential mode
Software-selectable ±20 V, G=1
±10 V, G=2
±5 V, G=4
±4 V, G=5
±2.5 V, G=8
±2.0 V, G=10
±1.25 V, G=16
±1.0 V, G=20
Throughput (Note 2) Software paced 250 S/s typ, PC-dependent
Hardware paced 50 kS/s
Channel gain queue Up to 16 elements Software configurable channel, range, and gain.
Resolution (Note 3) Differential 12 bits, no missing codes
Single-ended 11 bits
CAL accuracy CAL = 2.5 V ±36.25 mV max
Integral linearity error ±1 LSB typ
Differential linearity error ±0.5 LSB typ
Repeatability ±1 LSB typ
CAL current Source 5 mA max
Sink 20 µA min, 100 µA typ
Trigger source Software-selectable External digital: TRIG_IN
Pacer source Software-selectable  Internal
 External (SYNC), rising edge triggered
 Programmed IO
Note 1: Input current is a function of applied voltage on the analog input channels. For a given input
voltage, V
in
, the input leakage is approximately equal to (8.181*V
in
– 12) µA.
Note 2: Maximum throughput scanning to PC memory is machine dependent.
Note 3: The AD7870 converter only returns 11-bits (0 to 2047 codes) in single-ended mode.