Motore di ricerca datesheet componenti elettronici |
|
AD598A Scheda tecnica(PDF) 5 Page - Analog Devices |
|
AD598A Scheda tecnica(HTML) 5 Page - Analog Devices |
5 / 16 page AD598 REV. A –5– a voltage proportional to position. This technique uses the pri- mary excitation voltage as a phase reference to determine the polarity of the output voltage. There are a number of problems associated with this technique such as (1) producing a constant amplitude, constant frequency excitation signal, (2) compensating for LVDT primary to secondary phase shifts, and (3) compen- sating for these shifts as a function of temperature and frequency. The AD598 eliminates all of these problems. The AD598 does not require a constant amplitude because it works on the ratio of the difference and sum of the LVDT output signals. A constant frequency signal is not necessary because the inputs are rectified and only the sine wave carrier magnitude is processed. There is no sensitivity to phase shift between the primary excitation and the LVDT outputs because synchronous detection is not em- ployed. The ratiometric principle upon which the AD598 oper- ates requires that the sum of the LVDT secondary voltages remains constant with LVDT stroke length. Although LVDT manufacturers generally do not specify the relationship between VA+VB and stroke length, it is recognized that some LVDTs do not meet this requirement. In these cases a nonlinearity will result. However, the majority of available LVDTs do in fact meet these requirements. The AD598 utilizes a special decoder circuit. Referring to the block diagram and Figure 6 below, an implicit analog comput- ing loop is employed. After rectification, the A and B signals are multiplied by complementary duty cycle signals, d and (I–d) respectively. The difference of these processed signals is inte- grated and sampled by a comparator. It is the output of this comparator that defines the original duty cycle, d, which is fed back to the multipliers. As shown in Figure 6, the input to the integrator is [(A+B)d]B. Since the integrator input is forced to 0, the duty cycle d = B/(A+B). The output comparator which produces d = B/(A+B) also con- trols an output amplifier driven by a reference current. Duty cycle signals d and (1–d) perform separate modulations on the reference current as shown in Figure 6, which are summed. The summed current, which is the output current, is IREF × (1–2d). Since d = B/(A+B), by substitution the output current equals IREF × (A–B)/(A+B). This output current is then filtered and converted to a voltage since it is forced to flow through the scal- ing resistor R2 such that: V OUT = I REF × ( A – B )/( A + B ) × R 2 CONNECTING THE AD598 The AD598 can easily be connected for dual or single supply operation as shown in Figures 7 and 12. The following general design procedures demonstrate how external component values are selected and can be used for any LVDT which meets AD598 input/output criteria. Parameters which are set with external passive components in- clude: excitation frequency and amplitude, AD598 system bandwidth, and the scale factor (V/inch). Additionally, there are optional features, offset null adjustment, filtering, and signal in- tegration which can be used by adding external components. COMP COMP FILT FILT ∑ COMP ∑ RTO OFFSET FILT ∑ INTEG V TO I BANDGAP REFERENCE INPUT INPUT ±1 ±1 A d B 0<d<1 BINARY SIGNAL d - DUTY CYCLE (A+B) d–B q B A+B 1–d I REF d I REF q A–B A+B VOLTS OUTPUT VOUT = RSCALE x I REF x A–B A+B INTEG V TO I 1–d d V TO I Figure 6. Block Diagram of Decoder |
Codice articolo simile - AD598A |
|
Descrizione simile - AD598A |
|
|
Link URL |
Privacy Policy |
ALLDATASHEETIT.COM |
Lei ha avuto il aiuto da alldatasheet? [ DONATE ] |
Di alldatasheet | Richest di pubblicita | contatti | Privacy Policy | scambio Link | Ricerca produttore 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 |