Configuration and Installation
Chapter 2
AT-MIO-16D User Manual
2-26
© National Instruments Corporation
Instrumentation
Amplifier
+
+
-
-
Vin +
Vin -
Vm Measured
Voltage
Vm = [ Vin + Vin -
-
] * GAIN
Figure 2-26. AT-MIO-16D Instrumentation Amplifier
The AT-MIO-16D instrumentation amplifier applies gain, common-mode voltage rejection, and
high-input impedance to the analog input signals connected to the AT-MIO-16D board. Signals
are routed to the positive (+) and negative (-) inputs of the instrumentation amplifier through input
multiplexers on the AT-MIO-16D. The instrumentation amplifier converts two input signals to a
signal that is the difference between the two input signals multiplied by the gain setting of the
amplifier. The amplifier output voltage is referenced to the AT-MIO-16D ground. The
AT-MIO-16D ADC measures this output voltage when it performs A/D conversions.
All signals must be referenced to ground somewhere, either at the source device or at the
AT-MIO-16D. If you have a floating source, you must use a ground-referenced input connection
at the AT-MIO-16D. If you have a grounded source, you must use a nonreferenced input
connection at the AT-MIO-16D.
Types of Signal Sources
When configuring the input mode of the AT-MIO-16D and making signal connections, you must
first determine whether the signal source is floating or ground-referenced. These two types of
signals are described in the following sections.
Floating Signal Sources
A floating signal source is one that is not connected in any way to the building ground system but
rather has an isolated ground reference point. Some examples of floating signal sources are
outputs of transformers, thermocouples, battery-powered devices, optical isolator outputs, and
isolation amplifiers. The ground reference of a floating signal must be tied to the AT-MIO-16D
analog input ground in order to establish a local or onboard reference for the signal. Otherwise, the
measured input signal varies or appears to float. An instrument or device that provides an isolated
output falls into the floating signal source category.
Summary of Contents for AT-MIO-16D
Page 16: ......
Page 23: ......
Page 185: ......
Page 206: ......
Page 207: ......
Page 208: ......
Page 209: ......
Page 210: ......
Page 211: ......
Page 212: ......
Page 213: ......
Page 214: ......
Page 215: ......
Page 216: ......
Page 217: ......
Page 218: ......
Page 219: ......
Page 220: ......
Page 221: ......
Page 222: ......
Page 223: ......
Page 224: ......
Page 225: ......
Page 226: ......
Page 227: ......
Page 228: ......
Page 229: ......
Page 230: ......
Page 231: ......
Page 232: ......
Page 233: ......
Page 234: ......
Page 235: ......
Page 236: ......
Page 237: ......
Page 238: ......
Page 239: ......
Page 240: ......
Page 241: ......
Page 242: ......
Page 243: ......
Page 244: ......
Page 246: ......
Page 247: ......
Page 248: ......
Page 249: ......
Page 250: ......
Page 251: ......
Page 252: ......
Page 253: ......
Page 254: ......
Page 255: ......
Page 256: ......
Page 257: ......
Page 258: ......
Page 259: ......
Page 260: ......
Page 261: ......