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TMP17FS 数据表(PDF) 6 Page - Analog Devices |
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TMP17FS 数据表(HTML) 6 Page - Analog Devices |
6 / 8 page TMP17 REV. 0 –6– TMP17 VT AVG (1mV/K) TMP17 +5V 333.3 Ω (0.1%) VT AVG (10mV/K) 10k Ω (0.1%) +15V TMP17 TMP17 Figure 13. Average and Minimum Temperature Connections The circuit of Figure 14 demonstrates a method in which a voltage output can be derived in a differential temperature measurement. R1 50k Ω 10k Ω OP196 VOUT = (T1 – T2) x (10mV/oC) 10k Ω 5M Ω –V +V TMP17 TMP17 Figure 14. Differential Measurements R1 can be used to trim out the inherent offset between the two devices. By increasing the gain resistor (10 k Ω) temperature measurements can be made with higher resolution. If the magnitude of V and V is not the same, the difference in power consumption between the two devices can cause a differential self-heating error. Cold junction compensation (CJC) used in thermocouple signal conditioning can be implemented using a TMP17 in the circuit configuration of Figure 15. Expensive simulated ice baths or hard to trim, inaccurate bridge circuits are no longer required. OP193 REFERENCE JUNCTION 100k Ω 10k Ω VOUT +7.5V MEASURING JUNCTION 1k Ω TMP17 R THERMOCOUPLE TYPE APPROX. R VALUE J K T E S R 52 Ω 41 Ω 41 Ω 61 Ω 6 Ω 6 Ω 2.5V REF43 RG1 RG2 (1k Ω) Cu Cu Figure 15. Thermocouple Cold Junction Compensation The circuit shown can be optimized for any ambient tempera- ture range or thermocouple type by simply selecting the correct value for the scaling resistor – R. The TMP17 output (1 µA/K) times R should approximate the line best fit to the thermocouple curve (slope in V/ °C) over the most likely ambient temperature range. Additionally, the output sensitivity can be chosen by selecting the resistors R G1 and RG2 for the desired noninverting gain. The offset adjustment shown simply references the TMP17 to °C. Note that the TC’s of the reference and the resistors are the primary contributors to error. Temperature rejection of 40 to 1 can be easily achieved using the above technique. Although the TMP17 offers a noise immune current output, it is not compatible with process control/industrial automation current loop standards. Figure 16 is an example of a tempera- ture to 4–20 mA transmitter for use with 40 V, 1 k Ω systems. In this circuit the 1 µA/K output of the TMP17 is amplified to 1 mA/ °C and offset so that 4 mA is equivalent to 17°C and 20 mA is equivalent to 33 °C. Rt is trimmed for proper reading at an intermediate reference temperature. With a suitable choice of resistors, any temperature range within the operating limits of the TMP17 may be chosen. TMP17 REF01E 35.7k Ω 10mV/ C 10k Ω 12.7k Ω 5k Ω 500 Ω +20V –20V VT 10 Ω C RT 5k Ω 1mA/ C OP97 17 C ≈ 4mA 33 C ≈ 20µA Figure 16. Temperature to 4–20 mA Current Transmitter Reading temperature with a TMP17 in a microprocessor based system can be implemented with the circuit shown in Figure 17. R ROFFSET/RGAIN OP196 VOUT = 100mV/( C OR F) +5V REF43 V– C F ≈ 9.1kΩ ≈ 9.8kΩ 100k Ω 180k Ω RGAIN ROFFSET TMP17 RCAL 2.5V RGAIN ROFFSET Figure 17. Temperature to Digital Output By using a differential input A/D converter and choosing the current to voltage conversion resistor correctly, any range of temperatures (up to the 145 °C span the TMP17 is rated for) centered at any point can be measured using a minimal number of components. In this configuration the system will resolve up to 1 °C. |
类似零件编号 - TMP17FS |
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类似说明 - TMP17FS |
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