Zakładka z wyszukiwarką danych komponentów |
|
AD538SD Arkusz danych(PDF) 10 Page - Analog Devices |
|
AD538SD Arkusz danych(HTML) 10 Page - Analog Devices |
10 / 11 page AD538 –10– REV. C TRANSDUCER LINEARIZATION Many electronic transducers used in scientific, commercial or industrial equipment monitor the physical properties of a device and/or its environment. Sensing (and perhaps compensating for) changes in pressure, temperature, moisture or other physical phenomenon can be an expensive undertaking, particularly where high accuracy and very low nonlinearity are important. In conventional analog systems accuracy may be easily increased by offset and scale factor trims, however, nonlinearity is usually the absolute limitation of the sensing device. With the ability to easily program a complex analog function, the AD538 can effectively compensate for the nonlinearities of an inexpensive transducer. The AD538 can be connected be- tween the transducer preamplifier output and the next stage of monitoring or transmitting circuitry. The recommended proce- dure for linearizing a particular transducer is first to find the closest function which best approximates the nonlinearity of the device and then, to select the appropriate exponent resistor value(s). ARC-TANGENT APPROXIMATION The circuit of Figure 17 is typical of those AD538 applications where the quantity VZ /VX is raised to powers greater than one. In an approximate arc-tangent function, the AD538 will accu- rately compute the angle that is defined by X and Y displace- ments represented by input voltages VX and VZ. With accuracy to within one degree (for input voltages between 100 µV and 10 volts), the AD538 arc-tangent circuit is more precise than conventional analog circuits and is faster than most digital tech- niques. For a direct arc-tangent computation that requires fewer external components, refer to the AD639 data sheet. The circuit shown is set up for the transfer function: VV V V V REF Z X θθ θ =− () () () 121 . where: θ= Tan−1 Z X The (VθREF – Vθ) function is implemented in this circuit by adding together the output, Vθ, and an externally applied refer- ence voltage, VθREF, via an external AD547 op amp. The 1 µF capacitor connected around the AD547’s 100 k Ω feedback resistor frequency compensates the loop (formed by the ampli- fier between Vθ and VY). 25k 25k LOG RATIO 100 25k 25k ANTILOG LOG OUTPUT 100 AD538 INTERNAL VOLTAGE REFERENCE V = [V REF –V ] ( ) = TAN–1 ( ) VZ VX Z X 1.21 1 2 3 4 5 6 7 8 9 18 17 16 15 14 13 12 11 10 I VO IZ VZ B +10V +2V IY A D IX VX C PWR GND SIGNAL GND VY –VS IN4148 RATIO MATCH 1% METAL FILM RESISTORS FOR BEST ACCURACY * +VS 1 F 1 F +15V –15V V VZ AD547JH R2 * 100k +15V –15V 0.1 F 100k 1 F 118k R1 * 100k 10k FULL-SCALE ADJUST RA 931 , 1% VX Figure 17. The Arc-Tangent Function The VB/VA quantity is calculated in the same manner as in the one-quadrant divider circuit, except that the resulting quotient is raised to the 1.21 power. Resistor RA (nominally 931 Ω) sets the power or m factor. For the highest arc-tangent accuracy the external resistors R1 and R2 should be ratio matched; however, the offset trim scheme shown in other circuits is not required since nonlinearity effects are the predominant source of error. Also note that insta- bility will occur as the output approaches 90 ° because, by defini- tion, the arc-tangent function is infinite and therefore, the AD538’s gain will be extremely high. |
Podobny numer części - AD538SD |
|
Podobny opis - AD538SD |
|
|
Link URL |
Polityka prywatności |
ALLDATASHEET.PL |
Czy Alldatasheet okazała się pomocna? [ DONATE ] |
O Alldatasheet | Reklama | Kontakt | Polityka prywatności | Linki | Lista producentów All Rights Reserved©Alldatasheet.com |
Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
Family Site : ic2ic.com |
icmetro.com |