TIDUEA0A March   2019  – September 2020

 

  1.   1
  2.   Description
  3.   Resources
  4.   Features
  5.   Applications
  6.   6
  7. 1System Description
    1. 1.1 Key System Specifications
  8. 2System Overview
    1. 2.1 Block Diagram
    2. 2.2 Design Considerations
    3. 2.3 Highlighted Products
      1. 2.3.1 Device Recommendation
      2. 2.3.2 Digital Temperature Sensor - TMP117
      3. 2.3.3 Digital Temperature Sensor - TMP116
      4. 2.3.4 ESD Protection Devices
    4. 2.4 System Design Theory
      1. 2.4.1 PT100, PT500, PT1000 based Measurement in Heat Meters
      2. 2.4.2 TMP117 Configuration as Temperature Sensor
      3. 2.4.3 Digital RTD Solution Using TMP117
      4. 2.4.4 Ambient Temperature Considerations
  9. 3Hardware, Software, Testing Requirements, and Test Results
    1. 3.1 Required Hardware and Software
      1. 3.1.1 Hardware
      2. 3.1.2 Interface Test Software for TMP116
    2. 3.2 Testing and Results
      1. 3.2.1 Test Setup for Performance Testing
      2. 3.2.2 EMI and EMC Test Requirements for DRTD
      3. 3.2.3 TMP117 EMI/EMC Test Results
      4. 3.2.4 TMP117 Based Temperature Probe Measurement Performance Test Results
      5. 3.2.5 TMP116 Based Temperature Probe Measurement Performance Test Results
      6. 3.2.6 I2C-bus Cable Length Considerations
      7. 3.2.7 Power Supply
      8. 3.2.8 ESD Test Results for TMP116
      9. 3.2.9 Summary
  10. 4Design Files
    1. 4.1 Schematics
    2. 4.2 Bill of Materials
    3. 4.3 Layout Prints
    4. 4.4 Altium Project
    5. 4.5 Gerber Files
    6. 4.6 Assembly Drawings
  11. 5Software Files
  12. 6Related Documentation
    1. 6.1 Trademarks
  13. 7About the Author
  14. 8Revision History

TMP117 Based Temperature Probe Measurement Performance Test Results

For the following different test conditions, data is taken with the DRTD using both the TMP117 and TMP116 devices. The TMP117 is the recommended device due to the increased accuracy. However, since both temperature sensors will fit the application, data is shown for both. In this section, data was taken with 3 different TMP117 probes to ensure accurate results. See Section 3.2.5 for TMP116 probe results.

The DRTD probes were immersed into a precision Fluke oil bath with Galden HT200 oil, and ten values were read out for each temperature point. The measured range is from –20°C to 130°C in steps of 5 degrees C; the worst (largest) deviation from each of these ten values per step has been plotted for the respective temperature measurement point in Figure 3-5.

TIDA-010002 TMP117 DRTD –20°C to 130°C
                        Temperature Error DriftFigure 3-5 TMP117 DRTD –20°C to 130°C Temperature Error Drift.

TI's DRTD achieves class AA accuracy.

The Class AA accuracy achieved with this TIDA-010002 DRTD unit without calibration is not ensured for all TMP117 devices by default. Due to the average ±3σ spread of the devices (see the TMP117x High-Accuracy, Low-Power, Digital Temperature Sensor With SMBus- and I2C-Compatible Interface Data Sheet), a single-point calibration is needed to minimize the temperature offset, either at 0°C using an ice bath or at room temperature, for example. Figure 3-5 shows that a DRTD probe with the TIDA-010002 inside can meet the Class AA limits for temperature offset without calibration. This is assuming the specific device performs close to the average curve shown in the data sheet.

EN60751:2008 requires that all RTDs are checked at one temperature point between –5°C and 30°C, preferably at 0°C. Class A and Class AA thermometers, which utilize the TIDA-010002, require a second check at a temperature of 90°C above the first one; this could be 0°C and 90°C or 3°C and 93°C, for example.

As the response time of the temperature sensor is an important parameter for standard RTDs, the TIDA-010002 performance was measured in stirred oil and still air for comparison. Stirred oil results are relevant for applications where the DRTD has direct contact with the fluid, as is the case with Heat and Cooling Meters. In Figure 3-6 the TMP117 DUT has an average initial temperature of 22°C and is inserted into a 70°C hot oil bath and the DUT reported temperature has been logged.

TIDA-010002 TMP117 DRTD Response Time
                        in Stirred Oil BathFigure 3-6 TMP117 DRTD Response Time in Stirred Oil Bath.
The results for the three TMP117 probes is almost identical. It takes approximately 55 seconds for the probes to reach the oil temperature of 70°C. The still air response time of three DRTD probes is shown in Figure 3-7.

TIDA-010002 TMP117 DRTD Response Time
                        in Still AirFigure 3-7 TMP117 DRTD Response Time in Still Air.