rnrlog devices frx-on-dehrnd hotline - page 6 -. analog w devices i high perfonnance, isolated voltage-to-current converter . 2822 i features wide input range: 0 to +1v to 0 to +10v ..~tandard output range: 4 to 2oma high cmv input/output isolation: 1500v de continuous low nonlinearity: 0.05% max, 2b22l low span drift: o.oo5%fc max, 2b22l single supply: +14v to +32v meets ieee sui 472: transient protection (swc) meets isa s1ii 60.1: isolated current loop transmitters applications industrial instrumentation and process control ground loop elimination high voltage transient protaction d/a convertar - current loop interface anelog t...nsmittan and controllers remote da1a acquisition systems general description model 2b22 is a high performance, compact voltagc-to-cur- rent converter offering 1500y dc input to output isolation in interfacing standard process signals. the input stage of the model 2b22 is single resistor programmable to accept voltage ranges from 0 to +lv to 0 to +10y. the isolated output cur- rent range is 4 to 20ma, and the 2b22 can be operated with 0 to 100011 grounded or floating loads. using modulation techniques with transformer isolation for reliable performance, the 2b22 is available in three accuracy selections offering guaranteed nonlinearity error (2b22l: fo.os% max, 2b22k: :to. 1% max, and 2822j: :to.2% max) and guaranteed low span drift: :i:o.oos%/oc max, :to.ol %tc max, and :to.01s%i'c max, respectively. the internally trim- med span and offset errors are :to. 1 % max for the 2822l and :to.2s" max for the 2b22}/2b22k. both span and offset are adjustable by the optional external potentiometers. featuring a wide ransc. single supply operation (+ 14 y to +32y), the 2b22 provides isolated +28y loop power and is capable of delivering rated current into an external 0 to 100011 load resistance. the unique output stage configuration also al- lows the user to urilize an optional cxremalloop power supply to interface systems desjgncd for a two-wire operation. appucations model 2b22 has been specifically designed for high accuracy applications in process control and monitoring systems to offer compkte galvanic isolation and protection against damage from transients and fault voltages in transmitting information between subsystems or $cparated system clements. the 2b22 functional block diagram re' out "0 ... in )i)~r.iit ""'n "0 ""'" :..} ;:'.runt .-... _ill"'oo meets the requirements of the instrument society of america std. 50.1 "compatibility of analog signals for electronic industrial process instruments" for type 4, class u isolated current loop transmitters. in the industrial environment, model 2b22 can serve as a transmission link between such system elements as transmit- ters, indicators, controllers, recorders, computers, actuators and signal conditioners. in data acquisition and control sys- tems, the 2822 may act as an isolated interface between the d/a converter output of a microcomputer and standard 4 to '2oma analog loops. design features and user benefits high reliability: model 2b22 is a conservatively designed, compact module capable of reliable operation in harsh environments. to assure high reliability, the 2822 has a calculated mt8f of over 270,000 hours and has been de- signed to meet the ieee standard for transient voltage protection (472-1974: surge withstand capability). process signal compatibility: the versatile input stage design with a single resistor gain adjustment enables the 2822 to ac- cept anyone of tbe standard inputs-o-iv. o-ioy, 1-5y; or i-sma,4-20ma, la-soma; and provide standard, isolated 4-20ma output. isolated loop power. internal28y dc loop supply, completely isolated from the input power terminals (:t1500v dc isolation), provides the capability to drive 0 to 1 000111oads and elimi- nates the need for an external dc/dc converter. -1- obsolete
analog devices fax-on-dehand hotline - page 7 2822 -specifications (typical @ +25c and ys = j:15y unless otberwise noted) gain ~e muimum safe input input impedance output specifications qanent output iwije load resistance range, vs. +14v to +j2v, int;mal loop power maximum oucpu.t qanent, (tlnputoverioad output ripple, l00h.. bandwidth g-l.6man nonunearity (~ of span) cmv,inputtooutput ie, 6ohr., 1 minute duration continuous, .., ck de cmit, input to output 60&, lkn source jmbalanec accuracvi warm up time to raud performance 5 minura total output errodt +zs"ci ,3 offtet (vim -ov) :to.2s% max span (vim. +10v) to.25% max "'. temperatui'c (0 co +70. co g r 1.6man) ofaet (vim. ov) :to.ol%i'c max span (vim . ...10v) :to.o1s%i"c max vs. tanpcraaai'c (0 to +70.c) offra (vim. ov, g r 1.6man to 16ma/v) span (g = 1.6man to 16man):t dynamic response senjm,time - to o.l~of 1".5. for 10v step j~ slew rate o.o6malps reference input voltage input impedance oscillator frequency, internal oseillator extcmal sync input frequeney wavdonn model input specifications voltatlc sipillwijc, g-1.6man g-16man voltag" power supply volraae, rated pmormancc voltage, opcratina supply current (at fun sc:ak output) liiiniildrenw loop power uiidi exzzmal loop powlcl' supply change effm (" of span) on offset (vin . ov) on span (vim&+10v) tempera tuke range raud pcrormaace opcraw., stot8llc case size 2822j 0 to +iov oto+1v 1.6 co 16man +1sv 10mn 4t02oma 0 to 10000 max 2'ma 60$ta pk-pk :t.o.2~ max lsoov ims :t.1s00v pit max 9odb :to.ol~c :to.o1s%i'c +2.sv dc 6kn 100khz t 10% 100khz t 10% max . square wave, 50% duty cycle 20v p-p +1sv de +14v to +32v de l00ma soma :to.ooos"n :t.o.ooo5%n 0 to +70.c -2'.c to +7s.c -ss'c to +8soc z.2~ x t' x 0.6. nots . accunq i8 ., g. 1.6man wlda 110 ex..,'" ..... odi-a wind _e- u _d id ""'" 1. 'aii ,nq.'" df_w""~ "'... ..1ima(.0..". .o.oimaae,rod. 'sp...t.c. fo, pin.."", do... 1.6aaajv. kg """""""1<- .1_t.c. (doppml"c) kg ia f bat perf_....... .s,..cif"iciiiio.. oame u 2 a22j. spedftcadono oubjece to cia , without oocic:c- zb2%k 2b22l . . to.l% max to.os% max -2- outline dimensions dimensions shown in inches and (nun). t l~ g.20minfl.181 """"",i~ -j model 2822 ~ ~11',1) ~ a.04maxf77:l1 1 '.%im"" r , ",,'out .-.-.-.-. 2...fln r.e"" out 11 a iwn +-h-t- . cwn :: :"'rr, i . ........- ............... .._com em ._,"- "",,..ntour 12, ""'"' +vlooi' out ,. toiyiicou't' -v"",",ouj ,. odttooiv."" ."""t""'-, --i 1--'" (2"" grid interconnecfion diagram model 2822 can be applied directly to achieve rated performance as shown in figure 1 below. the input stage gain of 1.6man. to convert a 0 to +10v signal into a 4 to 2oma output current, is ob- tained with the values shown. a single polarity power supply (+14v to +32v de) should be connected to pin 8. to elimi- nate ground loops, the user should ensure that the signal return (common) lead does not carry the power supply current. pow- er common (pin 7) and signal common (pin 6) should be tied at the power supply common terminal. the voltage difference between pins 6 and 7 should not exceed o.2v. an internal dc-dc converter pro- vides isolated output loop power (pins 13 and 14), which is connected externally to the current output terminals (pins 11 and 12) and a load resistance. the standard 4 to 20ma curremoutput signal is delivered into any external load between zero and 10000. 2b22 ~ "ioiiy. ...... non, -- ro , ru - "". -,"c - fnio 1)po. v- foro' '-..n."" a-18ana1\1._'oppnorcr. -&a,pmrc ro. figure ,. basic connections :to.2s max to.t%max to.25% max to.l% max to.oos%l'c max to.oozs%l'c nwr to.ol%fc max :w.oos%fc max :t.o.oos%"'c :to.ooz5%i'c to.ol%fc to.oo5%/oc obsolete
analog devices fax-on-dehand hotline - page b applying the 2822 funcdonaldesouptwn the high performance of model 2822 is derived from the carrier isolation technique which is used to transfer both signal and power between the v ii converter's input circuitry and the output stage. high cmv isolation is achieved by the transform- er coupling between the input amplifier, modulator section and the current output circuitry. the block diagram for model 2822 is shown in figure 2 below. .-- the 2822 produces an isolated 4 to 20ma output current which is proportional to the voltage input and independent of the load resistance. the input amplifier operates single-ended and accepts a positive voltage within 0 to +10v range. gain can be set from 1.6man to 16man by changing the gain resistor ~ to accommodate input ranges from 0 to +lv (g = 16man) to 0 to -+iov (g = 1.6man). the transfer function is lout" (4ma + g xvln). an internal, high stability reference has nominal output volt- age of +2.5v (ref out) and is used to develop a 4ma output current for a 0 volts input. the terminals ref out (pin i) and ref in (pin 2) should be connected via the offset setting resistor ro. for ratiometric operation, an external reference voltage can be connected to the ref in terminal. the 2822 is designed to operate from a single positive power supply over a wide range of + 14v to +32v de. an internal dc-de converter provides isolated +28v loop power which is independent of +vs. the maximum resistance of the load rl (resistance of the receivers plus the resistance of the connec- ting wire) is 100011. since the loop power is derived from the input side, the current capability of the power supply (+vs> must be looma min to supply full output signal current. ""out .0 r~' in 'n) ~raiht :,2) ~mnr """" ooicillaroa figure 2. block diagram - 2b22 optional trim adjustments model 2822 is factory calibrated for a 0 to +10v input range (g.. 1.6ma/v). as shipped, the 2822 meets its listed specifica- tions without use of any external trim potentiometers. addi- tional trim adjustment capability, to reduce span and offset errors to ::1:0.05% max, is easily provided as shown in figure 3. the span and offset trim pots are adjusted while monitoring the voltage drop across a precision (or known) load resistor. the following trim procedure is recommended: 1. connect mood 2822 as shown in figure 3. 2. apply vjn = 0 volts and adjust ro (offset adjust) for vout=+2v::i:4mv. 3. apply vjn = +10.00v and adjust rc (span adjust) for vout = +10v ::i:4mv. ~ ~ ~ figure 3. optional span and offset adjustment gain and offset setting the gain of the 2822 is a scale factor setting that establishes the nominal conversion relationship to accommodate +lv to +10v full scale inputs (vln)' the value of the gain setting re- sistor rg is determined by: ~(ko) = 6.314sf/(io.l - sf) where sf is a scale factor equal to the value of vjn f .5. ex' ample: to convert a 0 to +lv input to the 4 to 2oma output, sf = 1 and rg = 69311. due to device tolerances, allowance should be made to vary rc by :ts% using the potentiometer. the value of the offset resistor ro is independent from the gain setting and given by the relationship: ro (kg) = 2.5 (vref - 2.4) where vref is the reference voltage applied. for example, the reference provided by the 2822 is +2.5v and therefore ro = 2500. the accuracy of the ro calculation from from the above formula is :1::5%. when an external reference operation is desired (i.e. for ratiometric operation), connect the reference voltage via ro to pin 2 and leave pin 1 open. external wop power operation for maximum versatility, the 2822's output stage is designed to operate from the optional, isolated external loop power sup- ply. this feature allows the user to interface systems wired for a two-wire operation. as shown in figure 4, the same wiring is used for loop power and output. the load resistance is con- nected in series with an external de power supply (+6v to +32v), and the current drawn from the supply is the 4 to 2oma output signal. the input stage of the 2822 still requires +vs power, but the currentdraln from +vs is limited to soma. use of an external loop power may require gain and offset trimming to obtain specified accuracy. the maximum series load resistance depends on the loop supply voltage as shown in figure 4. '100 j ,- i " ... . '" i' ... ... 0 . . ,. .. zo.. jo ,. 'jetea""l '",00> - vo... figure 4. optional external loop power operation -3- obsolete
rnrlog devices frx-on-dehrnd hotline - page 9 2822 synoironizing multiple 2822's in applications where multiple 2822's are used in close prox- imity, radiated individual oscillator frequencies may cause "beat frequency" related output errors. these errors can be eliminated by synchronizing multiple units by connecting the sync out (pin 10) terminal to the sync in (pin 9) terminal of the adjacent 2822. the sync out terminal of this "slaved" unit can be used to drive another adjacent 2822 (figure 5). for best accuracy, each 2822 should be retrim- med wiien synchronizing connections are used. to additional 282> figure 5. multiple 2822's synchronization output protection the current output terminals (pins 11 and 12) are protected from shorts up to +32v dc but in many industrial applications, it may be necessaty to protect the 4 to 20ma output from accidental shorts to ac line voltages in addition to back emf induced from long output connections. the circuit shown in figure 6 can be used for this purpose. the maximum per- missible load resistance will be lowered by a fuse resistance value when protection circuitry is utilized. '" "'~eht (11 2b22 figure 6. output protection circuitry connections applications in industrial measurement and control systems proccls signal isolator, in process control applications, model 2822 can be applied to interface standard process signals (e.g. i to 5ma, 4 to 20ma, 10 to 50ma, 1 to sv) and convert them to isolated 4 to 2oma output. a typical hook-up of model 2822 is illustrated in figure 7, showing input resistor iic":r::t aq-~~~; sf-v.. f.s, 'yo ... ~~g~1ic "r., equation accuiiacy is tw figure 7. process signal current isolator rc converring the current from a remote loop to a voltage in- put, and a span adjusnnent resistor kg. a value of rc should be selected to develop a minimum of + 1 v signal with full scale input current applied. for example, a san resistor converts the 4 to 20ma current input to a 200mv to i v voltage input, which the 2b22 isolates and converts to a 4 to 20ma output. the reference input (pin 2) is not connected since the process signal provides a desired offset. isolated d/a converter, model 2822 offers total ground isola- tion and protection from high voltage transients in interfacing di a converters to standard 4 to 2oma current loops. this requirement is common in a microcomputer-based control system. the voltage necessary to power the current loop can be derived from the same +15v supply that is used to power the d/a converter. the d/a converter, such as the 12-bit ad dac80, should be connected for operation on the unipolar 0 to +10v output range. this is shown in figure 8. after the load resistor connection has been made, the current loop can be calibrated using the offset and span adjustment potentio- meters associated with the 2822. first, a digital input code of all one's is loaded into the di a. and the offset adjustment potentiometer is adjusted for a current output of exacdy 4ma. then, a digital code of all zero's is loaded into the d/a. and the span adjustment potentiometer is adjusted for a voltage across the load that corresponds to a current of 20ma less 1 lsb (19.9961ma). .tiv , ""0 figure 8. d/a converter - isolated 4 to 2oma interface pressure transmitter: in figure 9, model 2822 is used in a pressure transmitter application to provide complete input- output isolation and avoid signal errors due to ground loop currents. the process pressure is monitored with a strain gage type pressure transducer interfaced by the analog devices' model2b30 transducer conditioner. the bridge excitation and system power is provided by the model 2835 triple output power supply. the high level voltage output of the 2830 is converted to the isolated 4 to 20ma current for transmission to a remote recorder or indicator. ,..sou.. toansouc." 0 figure 9. isolated pressure transmitter -4- obsolete
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