analog devices fax-on-dehand hotline - p". 10 .. analog devices ! programmable output, isolated voltage-to-current converter . 2823 i features wide input renge. resistor programmable "pin programmable output: 4 to 20ma or 0 to 20ma high cmv input/output isolation: :i: 1500v pk continuous low nonllneerity: :i:0.o5% mex (2b23ki low span drift: :i: 0.005%rc max (2b23ki singla supply operation: +14v to +28v small size: 1.8" x 2.4" x 0.6" meau ieee std. 472: transient protection (swc) meets isa std. so.1: isolated current loop transmitters appucations industriellnstrumentation and proeess control ground loop elimination transient voltage protection analog tr itters and controdars remote data acquisition systems general description the model 2b23 is . high perfonnance, low cost voltage to current converter featuring :i: 1500v pk input to output isolation for interfacing with standard process signals. the input stage of the 2b23 may be single resistor programmed to accept voltages within a 0 to + 10v range (+o.iv to + 10v full scale). the isolated output is pin programmable to provide current in the range of 4 to 20ma or 0 to 20ma and can be opersted with 0 to 800n grounded or floating loads. the 2b23 uses reliable transformer isolation techniques and is available in two accuracy selections offering guaranteed non- linearity error (2b23k: ;t 0.05% max, 2b23j: :i: 0.1% max) and guaranteed low span drift (2b23k: :i:0.oo5%/"c max, 2b23j: ;to.oi%/"c max). the internally trimmed span and offset errors arc ;to.1% for the 2b23k and :i:0.2s% for the 2b23j. both span and offset may be adjusted using optional external potentiometers. featuring wide range, single supply operation ( + 14v to + 28v dc), the 2823 provides isolated loop power, thus eliminating the need for an external dc/de converter. appucations model2b23 has been designed to provide high accuracy, versatility and low cost in industrial and laborstory system applications requiring isolated current transmission. the 2b23 meets the requirements of the instrument society of america std. so.i "compatibility of analog signals for electrouic industrial process instruments" and may serve .s a transmission link between such system elements as computers, controllers, actuators, re- corders and indicators. functional block diagram "'-,.<: ~-r. ,,)~ in data acquisition and control systems, the 2b23 may act as an isolated interface between the di a converter output of a micro- computer analog 1/0 and standard 4 to 2oma or 0 to 20ma analog loops. in prncess control sysrems, the 2823 may be used as a current output stage of a proportional controller to interface devices such as current-ta-position converters and current-ta- pneumatic transducers. design features and user benefits high cmv isolation: the 2b23 features high input to output galvanic isolarion to elintinate ground loops and offer protection against damage from. transients and fault voltages. its isolation battier will withstand continuous cmv of :i: isoov pk and isoov rids @ 60hz for 60 seconds. high reliability: to assure high reliability in harsh industrial environments, reliable magnetic isolation is used. the 2b23 meets the ieee standard for transient voltage prorection (472- 1974: surge withstand capability) and offets reliable operation over - 2s"c to + 8s"c remperalure range. versatility: the 2b23 can be easily tailored to the user's appli- cation, accommodating a wide range of input voltages, providing pin programmable, standard current outputs and offeriug wide range, single supply operation. small size: to conserve board space, the 2b23 is packaged in a compact, 1.8" x 2.4" x 0.6" module. -1- obsolete
analog devices fax-on-demand hotline - pag' 11 2823 - specifications (typical @ +2s'c and vs ;= :l:isv unless otherwise noted) model input specifications inpui volugc range faetorycalibratai full seale input transfer function (tf) fa?orycah'brated user programmable maxmiiun safe inpul input impedanee output speciflca nons current outpul range user seleeuble load r.,.;st,nce range internal loop power maximum output current @lnputov?load output noise 100hz bandwidth nonlinearity isolation cmv, inputlo outpui ,c,60hz,jmin continuous, ,c or dc transient protection cmr @60hz, ikl1sourcelmbalance accuracy' warm up timetoratedperformance totaloutputerror@ +25"c'" offsel(vn" ~ ov) span(vtn - + 10v) n. tempcraturc(olo +70"c) offsct,.4-20mamode ij-20mamode span. both moocs dynamic response scttlingtimetoo. l%offs for 10v step small signal bandwidth power supply voluge,raledperormance( + vs) vol_, operating supply current (@20ma0utput) supplycbangeeffect onoffsel and span environmental temperature range bled performance operating relative humidiry permil-std202,methed 103b rfllmmuniry 27mhz@5w@3fl case size lbl3j 010 + iov +o.ivminro+iovmax 1.6maiv 1.6malv102oomaiv ;,j5v 10mi1 4t02oma,oto20ma olo8ool1m", 22matyp 1.5~pk-pk ;,0.1%= j500vnns :t15oovpk ieee std. 472 (swc) 86db 5 minulcs ;,0.25%max :t 0.25% m,x ;,o.oi%i"cm'" ;,o.oi%l'cryp ;,o.oi%/"cmax 5ms 400hz +15vdc + 14v nnn 10 + 28vmax 75ma ;,0.ooi5%/v 010 +70'c -25"clo+85"c ;, 0.2% eitor :to.i%eitor 1.8' x 2.4' x 0.6' 2b23k :to.05%max(:t0.02%ryp) :to.i%max :to.i%mox :to.oo5o/.j"cmax ~o.oo5%i"cryp :to.oo5%/"cmax notes 'a=nc,... l ~" 0-- o-."'~ .,,-- t ~.- "~~o q ;i:=~ 1~~t- ..., 1 obsolete
analog devices fax-on-demand motline - po" i, applying the 2823 functional description the high performance of model 2b23 is derived from the carrier isolation technique which is used to transfer both sigoal and power between the vii convener's input circ;u;try and the output stage. high cmv isolarion is achieved by the rransformer coupling between the input amplifier stage, modulator, and current output circuirry. a block diagram of the 2823 is shown in figure i. .,,~~ '"~ figure 1. 2823 functional block diagram the model 2823 produces an isolated 4 to 20ma or 0 to 20ma output current which is proporrional to the input voltage and independent of the output load resistance. the input amplifier accepts a posirive voltage within the range of 0 to + 10v. the rransfer function of the input stage may be set from 1.6man to 200man (dependent upon the output current range desired) by changing the gain resistor r" connected between pins 5 and 7. an internal, high stability reference having a nominal output voltage of + 5v (ref out) is used to develop a 4ma output current for a 0 volts input. ref out (pin 3) and ref in (pin 4) should be connected via the offset scaling resistor ro. an output current bypass secrion allows sealing of the nominal 4 to 20ma outpnt current toa range of a to 20ma. this is accomplished by connecring the ontput range select pin (pin 12) to the lout pin (pin 10) thereby providing a bypass for the 4ma. for 4-20ma opetarion, the bypass pin is connected to lout common (pin ii). the 2823 is designed to opetate from a single posirive power supply (+ vs) over a range of + 14v to +28v de. the power supply secrion consists of an input voltage regulator, a dc/de convener, plus associated tecrifying and rutering circuirry. the dc/de converter generates isolated loop power which is independent of vs and capable of driving the maximum load resistance (re- sistance of receivers plus the resistance of counectiog wirc:) of soon. the current capability of the power supply ( + v s) must be 75ma minimum to supply full output sigoal current. basic intellconnections the 2823 may be applied to achieve rated performance as shown in figure 2. the transfer function af 1.6man, for conversion of the 0 to + 10v input signal into a 4 to 20ma output current, is oburined using the values shown (ro~ jold1, rsc= 30h1, r" open). fnr best performance, rsc should be a metal film, :to.1% tolerance, 25ppml"c resi..or and ro should be :t 1%, looppml"c. jl no ."v'nput'~""""ou'put e ,,"'v...max figure 2. basic interconnections a power supply (+ vs) is connected to pin 1. to avoid ground loops, the user should ensure that the input signal return (sig com) does not carry the power supply rerum currenr. power common (pin 2) and sigoal common (pin 5) should be ried at the power supply common ternaina!. optional trim adjustments model 2823 is factory calibrated for a 0 to + iov inpur range and an outpur of 4 to 20ma, meering its lisred specifications without use of any analog devices fak-on-denand hotline - p... 13 2823 oifset and output scalinal adjustments: after selecting the required input stage gain, tho 2b23 must then be configured for either 4 to 20ma or 0 to 20ma output corront range. figures 4a and 4b illustnte the respective methods for each. tho value of the offset mostor !to is indepoodc:nt from tho gain oetting and may be sdjusted by . series cermet pot. for fine sdjustment of the output corront, roc value should be trimmed as shown in figure 3. 2803 '. 48. 4-20ma output connections 4b. d-20ma output connections figure 4. 4-20malo-20ma scating connections using mul11ple 2b23s unlike other transfonncr-based isolator,;, the 2b23 does not require any synchronizing circuits to eliminate beat frequency rejated output error,; in multichannel applicotions. 'this is due to tho use of pulse-width modulation technique in the 2b23. radiated individuaj oscillator frequencies will have no effect upon performance, oven in situations reqwring multiple 2b23s to be located in cinoo prozimity to one another. for this reason, do provisions for extemalsyncbronization are necessary. output pkotec'ilon tho current output terminals (pins 10 and ii) are protected for reverse voltage and shona up to + 32v de but in mmy industrial applications it may he necessary to protect the 4 to 20ma from' aa:idental shorts to ac line voltages. tho circuit shown in figure s may be employed for this purpnoo. tho maximum permissible 1ood resistance will be lowered by a fuse resistance value wben protection circuitry is utilized. .. figure 5. output protection circuitry applica'ilons in figure 6, model 2b23 is used in multiloop application of the data acquisition and control system to proyide isolated corront interface to a recorder, indicator and a valve positioner. .- figure 6. multi/oop isolation in applications reqwring current to voltage conversion, the 2b23 may be used as shown in figure 7. an external -joy reference is used ro provide necessary input offset. 'this circuit will provide :t isoov isolation in converting 4-20ma into a 0 to + 10y output. the output measurement device must have a high input impedance to avoid losding error,;. figure 7. 4-20ma to 0 to + iov isolated converter -4- obsolete
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