With the plethora of smart sensors and the need for ever lower power, there's a big push recently to get products out the door that deliver it all to a wide range of applications. In industrial settings specifically, temperature is one of the most widely measured and transmitted elements -- but it can be a power-sucking exercise. Now there's a reference design on the shelf that delivers accurate measurements and consumes less than 3.2 mA.
The Novato MAXREFDES16# reference design from Maxim Integrated Products, is a 4-20 mA loop-powered temperature transmitted with HART Communication Protocol.
The transmitter's temperature range is -200°C to +850°C with better than ±0.1% or ±1.0°C accuracy. It supports 2-, 3-, or 4-wire resistance temperature detector (RTD) sensor inputs. The MCU fits into a DIN size B head-mounting enclosure so that it meets field sensor needs. Working with inputs from PT100 to PT1000, it can be used in a broad range of industrial control and automation applications.
Additional reference design features include:
- -40°C to +85°C operating range
- 0.03°C temperature resolution
- < 0.05% span error or ±0.2°C at +23°C (whichever is greater)
- 12V to 40V supply voltage range
- 200µA RTD excitation current
- Auto compensation of wire resistance for 3-wire RTD
- 10Ω to 1kΩ loop load
- Sensor burnout detection
– NAMUR down scale: < 3.2mA
– NAMUR up scale: programmable from 20.5mA to > 24mA
- Loop current limiter: 30mA ±5mA
AB Tech Solution developed the HART Communications Protocol. The HART stack for Novato runs on the Renesas RL78/G12 ultra-low power MCU, and supports universal and common-practice commands.
While there are many solutions on the market today that address temperature measurements, the challenge really is to find stable and reliable performance, while not adding to the power budget, all of which is especially difficult in the harsh environments of industrial settings.