Measurement Computing USB-1208FS-Plus - Manual (Page 21)

21
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 Condition Specification
A/D converter type Successive approximation type
Input voltage range for linear operation CHx to GND Single-ended mode: ±10 V max
Differential mode: –10 V min, +20 V max
Absolute maximum input voltage CHx to GND ±28 V max
Input impedance 122 kΩ
Input current (Note 1) V
in
= +10 V 70 µA typ
V
in
= 0 V –12 µA typ
V
in
= –10 V –94 µA typ
Number of channels 8 single-ended or 4 differential; software-selectable
Input ranges Single-ended ±10 V, G=2
Differential ±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
Software-selectable
Throughput (Note 2) Software paced 250 S/s typ, PC-dependent
Hardware paced 0.014 S/s to 50 kS/s
Channel gain queue Software selectable. 8 elements in SE mode,
4 elements in DIFF mode.
One gain element per channel. Elements must be
unique and listed in ascending order.
Resolution (Note 3) Differential 12 bits, no missing codes
Single-ended 11 bits
Integral linearity error ±1 LSB typ
Differential linearity error ±0.5 LSB typ
Repeatability ±1 LSB typ
Trigger source Software-selectable External digital: TRIG_IN
Software-selectable
Pacer source Software-selectable  Internal
 External (SYNC), rising edge triggered
Software-selectable
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 when scanning is machine dependent.
Note 3: The AD7870 converter only returns 11 bits (0 to 2,047 codes) in single-ended mode.