End-Equipment Solutions from TI... www.ti.com/sensors
Easily view full block diagrams, application notes, tools and software and other related information on the following sensor end-equipments.
- NEW Chemical/Gas Sensor
- UPDATED Field Transmitter: Pressure Sensor
- Field Transmitter: Temperature sensor
- Intelligent Occupancy Sensing
The output of the sensor is typically extremely small and needs to be suitably amplified and linearized (as needed) before it can be processed by any data acquisition system.
This signal conditioning of the sensor's raw output can be done in one of many ways. One way to implement is a discrete solution using op-amps/ instrumentation amps followed by a general purpose ADC. Alternately, one could use special purpose dedicated signal conditioning chips that give conditioned analog outputs. Analog front-end (integrated ADC solution) is the widely popular topology. Performance, resolution, board space, special functions and cost are some of the key parameters that help nail down the right architecture for a particular sensor type.
The type of signal conditioning and specific requirements for accurate capture of the sensor's output signal depends on the actual type of sensor measurement being made.
The following sections cover few of the popular sensor measurement techniques in detail:
Temperature sensor: Thermocouple
Temperature sensor: Thermistor
Temperature sensor: RTD
Pressure sensor
Weigh Scale
Flowmeter
Another aspect of precision signal chain requirements comes into play in driving the output of a sensor over a 4-20mA current loop.Current signals are not susceptible to noise because they avoid the potential voltage drops or electrical interference associated with voltage signals. A 4 to 20mA transmitter is converts the physical signal or measurement (such as temperature or pressure) into a 4mA to 20mA electrical signal for easier transmission to the control system. The signal is chosen so that a 4mA output corresponds to a 0% analog signal level, and 20mA will indicate a 100% analog signal output. The 4-20mA industry accepted standard allows for signal levels below 4mA and above 20mA to be used for fault diagnostics to alert the receiver to broken or faulty wire connections or sensor failures. Typical implementation of the 4-20mA loop includes a high precision, linear, low Iq DAC ( in case ADC is used on the input stage) and a 4-20mA transmitter. TI offers a variety of products that meet these requirements. Please see Recommended Solutions for the list of recommended devices pertaining to each sensor type.
| TI_Sensors_Guide.pdf |
