MAXREFDES42#：IO-LINK RTD温度传感器
概述
MAXREFDES42#为高精度IO-Link ®电阻温度检测器(RTD)的温度传感器的参考设计，用于较宽温度范围的2线、3线或4线PT100 RTD应用。按工业规格, 设计使用了Maxim Integrated高度集成的MAX31865 RTD至数字输出转换芯片。一个坚固的, 安装在板上的M12母连接器, 使现成的RTD可通过标准的M12加长电缆连接至电路板。温度传感器的温度转换精度达到15位分辨率，并具有多种故障检测功能。显示屏显示四舍五入至最接近的°C温度值，同时IO-Link通信跟踪和提供精确的温度值。传感器使用IQ2 Development的IO-Link器件堆栈与任何兼容1.1版IO-Link的主机通信。参考设计采用工业DC-DC降压型转换器，功耗最小。电路板也带一个公的M12连接器，用于通过标准M12电缆连接至IO-Link主机。将MAXREFDES42#连接至USB IO-link主机，例如IQ2 Development iqInterface® IO-Link主机(使用iqTool®软件)，允许利用PC进行评估。
关于更多信息及实验室测量数据，请参见“详细资料”标签页。从“设计资源”标签页可下载设计文件和固件。
特性
- EC 61131-9
- IQ2 IO-Link iqStack®器件
- 兼容IO-Link 1.1版
- 非易失存储器用于保存校准数据
- 故障监测
- LED显示屏用于快速读数(近似温度值)
- IO-Link提供精确温度值*
竞争优势
- 高精度
- 低功耗
- 低成本
*参见实验室测量数据。
应用
- 食品加工
- 化学加工
- 纺织制造
- 空气、燃气及液体温度测量
详情介绍
Introduction
Resistance temperature detectors (RTDs) are resistors that increase resistance when temperature increases. Accuracy, stability, and repeatability over a wide temperature range make RTDs excellent in a multitude of industrial applications. RTDs are made of many materials and often they are made of platinum to avoid corrosion and oxidation. The PT100 is one of the most popular RTDs where the resistance is approximately 100Ω at 0°C, hence the name PT100.
IO-Link is the first open, field bus agnostic, low-cost, point-to-point serial communication protocol, used for communicating with sensors and actuators, that has been adopted as an international standard (IEC 61131-9).1 IO-Link finally standardizes interoperability of industrial equipment from all over the world. IO-Link can directly function from the PLC or can be converted from all standard field busses to IO-Link through a gateway, quickly making it the defacto standard for universally communicating with smart sensors like the MAXREFDES42#.
Maxim Integrated and IQ2 Development collaborated in designing the MAXREFDES42# as an IO-Link version 1.1-compliant IO-Link RTD temperature sensor reference design. The MAXREFDES42# design consists of an industry-standard Maxim Integrated IO-Link device transceiver (MAX14821), an efficient high-voltage step-down converter (MAX15062B), a Renesas® ultra-low-power 16-bit microcontroller (RL78) utilizing IQ2 Development’s IO-Link device stack, and a highly integrated RTD-to-digital converter (MAX31865). Figure 1 shows the system block diagram.
Figure 1. The MAXREFDES42# reference design block diagram.
Detailed Description of Hardware
The MAXREFDES42# IO-Link RTD temp sensor consists of 4 main blocks: IO-Link transceiver, step-down converter, RTD-to-digital converter, and microcontroller as shown in Figure 1.
The MAX14821 IO-Link device transceiver is IO-Link version 1.1/1.0 physical layer compliant with configurable outputs (push-pull, pnp, or npn), reverse-polarity/short-circuit protection, and extensive fault monitoring, all in a tiny 2.5mm x 2.5mm WLP package.
The MAX15062B is a high-voltage, synchronous step-down converter that efficiently converts 24V to 5V in a tiny 2mm x 2mm, 8-pin TDFN package. The PWM operation maintains a constant frequency during all operating loads. The MAX15062 comes in many versions. The MAXREFDES42# temperature sensor uses the MAX15062B, which is preset for a 5V output.
The MAX31865 is an RTD-to-digital converter optimized for platinum RTDs. An external 400Ω 0.1% reference resistor (R13) with a typical temperature coefficient of 0.2ppm/°C sets the sensitivity for a PT100 RTD. If a PT1000 RTD is preferred, use a precision external 4kΩ resistor instead. The reference resistor value is also stored as an IO-Link parameter in the sensor and needs to match the corresponding reference resistor used. The highly integrated RTD-to-digital converter is available in a 20-pin TQFN package.
An ultra-low-power RL78/G1A microcontroller with current consumption down to 66µA/MHz provides system control. It features 64KB on-chip programmable flash memory, 4KB on-chip data flash, and operates down to 1.8V, all in a tiny 3mm x 3mm LGA package.
For protection, the MAXREFDES42# features transient voltage suppressor (TVS) diodes at the IO-Link interface. Transient voltage suppressor (TVS) diodes are not all equal. The SDC36 TVS diodes have a clamping voltage less than 55V and meet both IEC 61000-4-2 (ESD) and IEC 61000-4-4 (EFT). There are many smaller TVS diodes on the market that cannot meet these specifications.
The on-board female M12 connector allows off-the-shelf RTDs, such as an Omega PR-26E-3-100-A-M6-0150-M12-2 or PR-26A-3-100-A-M6-0150-M12-2, to connect to the board using a standard M12 extension cable as shown in Figure 2a. The reference design ships uncalibrated and comes with a 2-wire PT100 RTD located in the gray terminal block TB1. Important: If you connect an external RTD via the extension cable to the female M12 connector, you must remove the 2-wire RTD inside the gray terminal block TB1. The board also contains a male M12 connector for easy connection to a compliant IO-Link master using a standard M12 cable. The MAXREFDES42# typically consumes 11mA at 25°C.
Figure 2a. The MAXREFDES42# reference design with Omega 4-wire RTD and extension cable.
Description of Software
The MAXREFDES42# was verified using IQ2 Development’s iqTool software version 1.1.0.4, which comes with the purchase of the iqInterface IO-Link master hardware. IQ2 Development’s latest source code and documentation are available at the links below.
http://iq2-development.com/downloads
http://iq2-development.com/iqmaxrefdes42
For more information about IQ2 Development’s IO-Link device stack please contact them at:
To get going quickly, go to the Quick Start section below for step-by-step instructions on how to find the appropriate Quick Start Guide. Figure 3 shows a screenshot of the IQ2 Development IO-Link iqTool software.
Figure 2b. The MAXREFDES42# reference design connected to an IQ2 Development iqInterface IO-Link master.
Figure 3. IQ2 Development’s iqTool software version 1.1.0.4.
Detailed Description of Firmware
The MAXREFDES42# ships preprogrammed as a working IO-Link temperature sensor ready to connect to an IO-Link master. The firmware targets a Renesas RL78 microcontroller and follows the simple flowchart shown in Figure 4. The firmware is written in C using the IAR embedded workbench from IAR Systems and utilizes IQ2 Development’s IO-Link device stack.
Figure 4. The MAXREFDES42# firmware flowchart.
After hot plug-in, the MAXREFDES42# waits for a wake-up signal from the IO-Link master. After receiving the wake-up signal, the MAXREFDES42# synchronizes to the IO-Link master’s 230.4kbps baud rate (COM3). Communication parameters are exchanged. The MAXREFDES42# then starts a cyclic data exchange every 3ms by sending the sensor process data to the IO-Link master. If the sensor is removed, the IO-Link master will detect a missing sensor.
Detailed Description of Use Cases
There are two different use cases that should be considered before purchasing the MAXREFDES42#. Use case #1 simply includes the MAXREFDES42# with a user-supplied IO-Link master and an IO-Link cable as shown in Figure 5. The system is preprogrammed to operate in this configuration. Use case #2 is where the entire firmware development system is needed as shown in Figure 6.
Figure 5. Use case #1 is the MAXREFDES42# quick start system.
Table 1. Recommended Components Needed for Use Case #1
| Use Case #1 (MAXREFDES42# Quick Start System) | ||
|---|---|---|
| Company | Description | Orderable Part Number |
| Maxim Integrated | IO-Link RTD temp sensor (ships programmed) | MAXREFDES42# |
| IQ2 Development | iqInterface IO-Link master | IOL1-B-DMU-W-CP001 |
| Balluff | IO-Link cable (4-wire/2m) | BCC05MC |
Figure 6. Use case #2 is the MAXREFDES42# firmware development system.
Table 2. Recommended Components Needed for Use Case #2
| Use Case #2 (MAXREFDES42# Firmware Development System) | ||
|---|---|---|
| Company | Description | Orderable Part Number |
| Maxim Integrated | IO-Link RTD temp sensor (ships programmed) | MAXREFDES42# |
| Maxim Integrated | E1 to MAXREFDES42# adaptor | MAXREFDES23DB# |
| IQ2 Development | iqInterface® IO-Link® master | IOL1-B-DMU-W-CP001 |
| Renesas Electronics | E1 programmer/debugger | R0E000010KCE00 |
| Balluff | IO-Link cable (4-wire/2m) | BCC05MC |
| IAR Systems | IDE and optimizing C/C++ compiler for RL78 | Renesas RL78 |
Quick Start (Use Case #1)
Required Equipment:
Purchased from Maxim:
- MAXREFDES42# board
User supplied:
- Windows® PC with a USB port
- IQ2 Development iqInterface IO-Link master
- IQ2 Development’s iqTool (tested with version 1.1.0.4 and comes with IO-Link master)
- M12 4-pin IO-Link cable (BCC05MC)
Note: Verify with IQ2 Development that your version of Windows is supported before purchasing their software.
Download, read, and carefully follow each step in the MAXREFDES42# Quick Start Guide.
Lab Measurements
Equipment Used:
- Windows 7 PC with USB port
- MAXREFDES42# board
- IQ2 Development iqInterface IO-Link master
- IQ2 Development’s iqTool (tested with version 1.1.0.4 and comes with IO-Link master)
- M12 4-pin IO-Link cable
- RD42_RL78_V01_00.ZIP ; where XX_XX = latest version from webpage
- Fluke 7341 calibration bath
- Omega HH41 thermometer
- ETI Therma 1 thermometer
- Fluke 189 multimeter
The lab measurements were taken using the setup and equipment shown in Figure 7.
Figure 7. Setup and equipment used for lab measurements.
Figure 8 shows error versus temperature referenced to the Omega HH41 thermometer and the ETI Therma 1 thermometer, respectively. The MAXREFDES42# connected RTD probe was placed in the Fluke 7341 and calibrated at 25°C. Click on the link below to see the NIST traceable certificate of calibration for the Omega HH41 thermometer used as a reference.
NIST traceable certificate of calibration for the Omega HH41 thermometer
Figure 9 shows the MAXREFDES42# temp sensor’s 24V supply current versus temperature, demonstrating stable, low-current consumption.
Figure 8. MAXREFDES42# Error vs Temperature, using a PR-26A-3-100-A-M6-0150-M12-2, 4-wire RTD calibrated at 25°C.
The red data used the Omega HH41 thermometer as a reference. The green data used the ETI Therma 1 thermometer as a reference.
Figure 9. MAXREFDES42# 24V Supply Current vs. Temperature.
References
- IO-Link System Description 2013 by IO-Link Company Community. Page 3, Preface.
IO-Link is a registered trademark of ifm electronic GmbH.
iqInterface, iqStack, iqTool are registered trademarks of IQ2 Development GmbH.
Renesas is a registered trademark and registered service mark of Renesas Electronics Corp.
Windows is a registered trademark and registered service mark of Microsoft Corp.