TABLE OF CONTENTS Analog Devices Technical Staff Walt Kester, Editor
Typically a sensor cannot be directly connected to the instruments that record, monitor, or process its signal, because the signal may be incompatible or may be too weak and/or noisy. The signal must be conditioned i.e., cleaned up, amplified, and put into a compatible format.
The following sections discuss the important aspects of sensor signal conditioning.
Excerpted from Practical Design Techniques for Sensor Signal Conditioning , Analog Devices, Inc., www.analog.com.
This section discusses the fundamental concepts of bridge circuits.
Resistive elements are some of the most common sensors. They are inexpensive to manufacture and relatively easy to interface with signal conditioning circuits. Resistive elements can be made sensitive to temperature, strain (by pressure or by flex), and light. Using these basic elements, many complex physical phenomena can be measured, such as fluid or mass flow (by sensing the temperature difference between two calibrated resistances) and dew-point humidity (by measuring two different temperature points), etc. Bridge circuits are often incorporated into force, pressure and acceleration sensors.
Sensor elements resistances can range from less than 100 ? to several hundred k ?, depending on the sensor design and the physical environment to be measured (See Figure 4.1.1). For example, RTDs (resistance temperature devices) are typically 100 ? or 1000 ? Thermistors are typically 3500 ? or higher.
| 120 ?, 350 ?, 3500 ? |
| 350 ? 3500 ? |
