Datenblatt-Suchmaschine für elektronische Bauteile |
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OP290 Datenblatt(PDF) 10 Page - Analog Devices |
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OP290 Datenblatt(HTML) 10 Page - Analog Devices |
10 / 12 page OP290 Rev. C | Page 10 of 12 APPLICATIONS INFORMATION TEMPERATURE TO 4 MA TO 20 mA TRANSMITTER A simple temperature to 4 mA to 20 mA transmitter is shown in Figure 20. After calibration, the transmitter is accurate to +0.5°C over the −50°C to +150°C temperature range. The transmitter operates from 8 V to 40 V with supply rejection better than 3 ppm/V. One half of the OP290 is used to buffer the VTEMP pin while the other half regulates the output current to satisfy the current summation at its noninverting input. × × × − × + = R10 R2 R7 R6 R2 V R10 R2 R7 R V I SET TEMP OUT ) 6 ( (1) The change in output current with temperature is the derivative of the following transfer function: R10 R2 R7 (R6 T V T I TEMP OUT × + ∆ ∆ = ∆ ∆ ) (2) From Equation 1 and Equation 2, it can be seen that if the span trim is adjusted before the zero trim, the two trims are not interactive, which greatly simplifies the calibration procedure. Calibration of the transmitter is simple. First, the slope of the output current vs. temperature is calibrated by adjusting the span trim, R7. A couple of iterations may be required to ensure that the slope is correct. Once the span trim has been completed, the zero trim can be made. Remember that adjusting the offset trim does not affect the gain. The offset trim can be set at any known temperature by adjusting R5 until the output current equals ( ) mA 4 + − ∆ ∆ = MIN A OPERATING FS OUT T T T I I Table 5 shows the values of R6 that are required for various temperature ranges. Table 5. Temperature Range R6 (k Ω) 0°C to +70°C 10 −40°C to +85°C 6.2 −50°C to +150°C 3 1/2 OP290GP VIN VOUT VTEMP GND 6 3 2 4 10k Ω R1 REF43 2N1711 V+ 8V TO 40V 1N4002 SPAN TRIM R10 100 Ω 1%, 1/2W R9 100k Ω R8 1k Ω R3 100k Ω R5 5k Ω R2 1k Ω VTEMP 4 8 2 3 ZERO TRIM VSET R4 20k Ω R6 3k Ω R7 5k Ω IOUT RL 7 6 5 1 1/2 OP290GP Figure 20. Temperature to 4 mA to 20 mA Transmitter |
Ähnliche Teilenummer - OP290_15 |
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Ähnliche Beschreibung - OP290_15 |
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