Single Chip 2-Wire Loop Powered: 4 to 20mA Current Loop RTD Temperature Transmitter Reference Design
Description
In general: for portable 2-wire 4 to 20mA current loop applications: the system power consumption needs to be considered carefully. The conventional approach of using a high bridge excitation voltage and an operational amplifier to achieve a full-scale ADC input voltage increases chip count and overall power consumption. An additional external voltage regulator is also needed to excite the bridge sensor and supply the microcontroller from the same voltage source. Since the goal for this reference design is to maintain low power consumption and low cost solution. This solution utilizes the integrated ADC and operational amplifiers (OAs) of a microcontroller. In order to cut down the cost: the ADC/DAC use the main supply voltage as its reference voltage instead of including an external reference or selecting a more expensive ADC/DAC that features an internal reference. Leveraging the integrated peripherals of MCU enables low component count and low cost. This reference design is based on a mixed signal microcontroller: specifically an MSP430F2274.
Features
- Analog functionality fully integrated into microcontroller Sensor input compatible with 2-wire PT100 RTD probe only Temperature range for RTD -200 °C to +850 °C Input power supply range: 10V to 33V DC 4 to 20mA current loop output signal Maximum measured error: better than ±2.5ºC Implements ratiometric measurement Design to meet IEC 61000-4 requirement Operating temperature range -40 °C to +85 °C
Applications
- Temperature transmitter
- Process analytics
- HVAC controller
- Level transmitter
- Position sensor
- Proximity switch
- Access control
- Safety area scanner
- Force & torque sensor
- Safety light curtain
- Flow transmitter
- Pressure transmitter
Product Categories
| Part Number | Name | Companion Part | |
|---|---|---|---|
| MSP430F2274 | MSP430F2274 | Buy Datasheet |
| Download the bill of materials for TIDA-00247 | Download |
Test Data
Get results faster with test and simulation data that's been verified.
Download the test file for TIDA-00247| Title | Updated | Type | Size (KB) | |
|---|---|---|---|---|
| Temperature Transmitter on Single Chip Mixed-Signal MCU CAD Files | 30 Jan 2015 | ZIP | 1222 | |
| Temperature Transmitter on Single Chip Mixed-Signal MCU Layer Plots | 30 Jan 2015 | 161 | ||
| Temperature Transmitter on Single Chip Mixed-Signal MCU Gerber Files | 30 Jan 2015 | ZIP | 301 | |
| Temperature Transmitter on Single Chip Mixed-Signal MCU Bill of Materials (BOM) | 30 Jan 2015 | 43 | ||
| Temperature Transmitter on Single Chip Mixed-Signal MCU Schematic | 30 Jan 2015 | 653 |