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datel, inc., mansfield, ma 02048 (usa) ? tel: (508)339-3000, (800)233-2765 fax: (508)339-6356 ? email: sales@datel.com ? internet: www.datel.com features figure 1. DMS-20lcd series simplified schematic DMS-20lcd series, 3? digit, lcd display, digital voltmeters represent the ultimate combination of low price, low power, small size and high performance in digital meters. epoxy encapsulated in a subminiature (1.38" x 0.88" x 0.43"), 12-pin dip package, these completely self-contained, fully operational meters offer a combination of ruggedness, long-term reliability and component-like ease-of-use simply not available in any other meters. incorporating a precision reference and a factory-calibrated, autozeroing a/d converter, DMS-20lcd meters are extremely accurate (1 count) and are only slightly larger than their 0.37"/9.4mm, enhanced-contrast, lcd displays. all models incorpo- rate a built-in bezel and are easily mounted in either panels or pc boards. both backlit and non-backlit versions are available. DMS-20lcd meters have 4 differential input voltage ranges (200mv, 2v, 20v and 200v) and a user-friendly input structure. input impedance is a minimum 800k ? . cmrr is typically 86db with a cmv of 2v. non-inverting inputs are overvoltage protected to 100v (250v for the 200v input model). all DMS-20lcd meters operate from a single +5v supply (drawing 400a) or a single +9v supply/battery (drawing 230a). all models have a low-battery ("b") annunciator and feature autopolarity changeover and overrange indication. also available is an application/evaluation board (dms-eb2) that plugs directly onto the back of any DMS-20lcd allowing direct inputs for common applications such as 4-20ma inputs, zero/gain adjust, decimal point location, and input voltage dividing. ? ? ? ? ? lowest cost ? ? ? ? ? lowest power, 2mw ? ? ? ? ? subminiature size: 1.38" x 0.88" x 0.43" 35mm x 22mm x 11mm ? ? ? ? ? large (0.37"/9.4mm), enhanced- contrast lcd display ? ? ? ? ? backlit displays optional ? ? ? ? ? epoxy-encapsulated, 12-pin dip ? ? ? ? ? panel or pc-board mountable ? ? ? ? ? 4 differential input voltage ranges ? ? ? ? ? high accuracy, 1 count (0.05%) ? ? ? ? ? single +5v supply or 9v battery ? ? ? ? ? low-battery annunciator ? ? ? ? ? user-selectable decimal point placement ? ? ? ? ? 0 to +60c temperature range 3? digit, lcd display low-cost, subminiature digital panel voltmeters DMS-20lcd series actual size (+) input hi (C) input lo analog common reference out reference in +5v supply/ +battery r1 dp 1 dp 2 dp 3 6 5 4 9 11 12 10 8 7 1 3 dc/dc converter 2 5v return/ Cbattery +5v C5v r2 +2.0v data 909k v+ vC a/d converter 0 vdc 0.01f n.c. r2 is not used on 200mv (-0) models or 2v (-1) models. r2 = 100k on 20v (-2) models and 9.1k on 200v (-3) models. j1 dc/dc converter is not used on 9v-powered models, j1 is connected. n.c./backlight used on backlit models only. n.c. for non-backlit models. +5v only used on 200mv (-0) and 2v (-1) models. 1 2 3 1 2 4 3 4 ?? www.datel.com
2 DMS-20lcd 3? digit, lcd display digital panel voltmeters performance/functional specifications typical at t a = +25c and supply voltage = +5v (using the single-ended input circuit) or +9v (using the differential input circuit), unless otherwise noted. ? applies for transient or continuous overvoltages applied to (+) input hi (pin 11) with (C) input lo (pin 12) properly connected. pin 12 is not overvoltage protected (see figure 1). voltages applied to pin 12 should not exceed the supply voltage. ? listed spec applies to 5v-powered models only. for 9v-powered models, both (C) input lo (pin 12) and (+) input high (pin 11) must always be at least 1.5v above Cbattery (pin 3) and at least 1.5v below +battery (pin 1). ? see technical notes. leave blank for standard models. add b for backlit models. DMS-20lcd - 1 - 5 accessories: DMS-20-cp panel cutout punch dms-bzl3 DMS-20 bezel assembly dms-bzl4 DMS-20 bezel assembly with sealing gasket dms-eb2 application/evaluation board with standard molex connector, decimal point solder pads and attenuation resistor pads. dms-ps1-cm +5v/1.0a ac/dc power supply module input range: 0 = 200mv 1 = 2v 2 = 20v 3 = 200v power source: 5 = +5v 9 = +9v technical notes 1. reference output (pin 8) and input (pin 7): pin 8 is a precision reference actively trimmed at the factory. in normal operation, pin 8 must be tied to pin 7 to achieve all listed accuracy and drift specifications. 2. analog common (pin 10): this pin is connected to an internal, low-noise, "relative" ground. it is used in certain differential and "floating" measurements as described in the applications section of this data sheet and ap note 3 of the datel panel meter catalog. pin 10 should not be connected to pin 3 (5v return/?battery) or to your system's analog ground. 3. decimal point placement: the location of the decimal point is user-selectable, and the decimal point control pins (dp1-dp3) are active low functions. select the appropriate decimal point by tying the appropriate pin (pin 4, 5 or 6) to pin 3 (5v return/ Cbattery). unused decimal point location pins should be left open. for 5v-powered models, the decimal location pins are ttl compatible and may be hard wired as described above or driven with 5v ttl logic gates. ordering information a panel-mount retaining clip is supplied with each model. analog inputs min. typ. max. units full scale input range: DMS-20lcd-0 -- 200 -- mv DMS-20lcd-1 -- 2 -- volts DMS-20lcd-2 -- 20 -- volts DMS-20lcd-3 -- 200 -- volts input impedance: DMS-20lcd-0, -1 100 1000 -- m ? DMS-20lcd-2, -3 0.8 1 -- m ? overvoltage protection: ? DMS-20lcd-0, -1, -2 -- -- 100 volts DMS-20lcd-3 -- -- 250 volts common mode voltage range ? -- -- 2 volts cmrr (dc to 60hz) -- 86 -- db control inputs ? decimal point placement (pins 4-6): functionality tie to pin 3 to activate logic compatibility ttl (on 5v-powered models) backlight (pin 9) tie to pin 3 to turn on backlight performance sampling rate 2.5 samples per second accuracy (1 minute warm-up): DMS-20lcd-0 (v in = +0.19v) -- 1 2 counts DMS-20lcd-1 (v in = +1.9v) - - 1 2 counts DMS-20lcd-2 (v in = +19v) -- 2 3 counts DMS-20lcd-3 (v in = +190v) -- 2 3 counts zero reading (v in = 0 volts) "C 001" "000" "001" temperature drift (0 to +60c) -- 0.2 0.4 cnts/c power supply requirements (5v models) supply voltage +4.75 +5.00 +5.25 volts supply current: standard models -- +400 +600 a backlit models -- +35 +50 ma power supply requirements (9v models) supply voltage +7.5 +9.0 +14.0 volts supply current: standard models -- +230 +350 a backlit models -- +35 +50 ma display display type and size 3? digit lcd, 0.37"/9.4mm high polarity indication autopolarity ("C" for negative v in ) overrange indication "C1_ _ _ " for negative v in "1_ _ _ " for positive v in physical/environmental operating temperature 0 -- +60 c storage temperature C20 -- +75 c humidity (non-condensing) 0 -- 95 % case material polycarbonate weight 0.4 ounces (11 grams) order on-line at www.datel.com
3 3? digit, lcd display digital panel voltmeters DMS-20lcd DMS-20lcd meters are available in either 5v-powered or 9v- powered models. 9v devices operate directly from 7.5v to 14v supplies (usually batteries) without the need for external voltage regulators. 9v devices, however, can not be used to measure voltages referenced to the negative battery terminal (pin 3) because the minus input to the meter (pin 12, (C) input lo) must always be at least 1.5v above pin 3. 9v-powered meters can only be used to make differential and not single-ended measurements. 5v-powered devices operate from any well-regulated +5v supply and will accurately measure voltages both above and below pin 3 (5v return) in either single-ended or differential configurations. 1. single-ended input configurations: true single-ended measurements can only be made with 5v-powered meters. the circuit of figure 2 avoids problems normally associated with ground-loop currents. separate ground runs should be used for 5v return (pin 3) and (C) input lo (pin 12). 8. suggested mating connectors: panel mounted: connector housing datel p/n 39-2079400 terminal type datel p/n 39-2099090 crimping tool datel p/n 39-2099000 wire size 22 to 26 awg insulation diameter 0.062" (1.57mm) maximum stripping length 0.100 to 0.125" (2.54 to 3.17mm) board mounted: socket datel p/n 39-2359625 applications figure 2. single-ended input configuration (5v-powered models) r series = ohms +12.6 C 9.2v 0.035 example: if +battery (pin 1 with respect to pin 3) is +12.6v, +battery C 9.2v 0.035 r series = ohms r series = 97 ohms 5. low battery annunciator: the "b" annunciator in the upper left-hand corner of the display turns on when the supply voltage for 5v-powered models falls below approximately +3.75v or when the supply voltage for 9v-powered models falls below approximately 7.2v. this function can not be disabled. 6. gain adjust: there is a gain-adjust potentiometer on the back of each meter. it has approximately 50 counts (2.5%) range of adjustment. since these devices essentially have no zero/offset errors, a gain adjustment is effectively an overall accuracy adjustment. though they may be performed at any point (except zero), accuracy adjustments are most effective when performed with higher level input signals. the circuit shown in figure 9 provides 10% range of adjustment. 7. soldering methods: all models in the DMS-20lcd series easily withstand most common wave soldering operations. we recommend, however, that you evaluate the effects your particular soldering techniques may have on the meter's plastic case and high-precision electrical performance. we recommend the use of water-soluble solders and thorough cleaning procedures. 4. backlight (pin 9) function: grounding pin 9 (i.e. connecting it to pin 3) turns on the backlighting led's. for non-backlit models, pin 9 has no internal connection. all backlit models include internal current-limiting resistors. with nominal +5v or 9v supplies, backlit devices typically draw 35ma of supply current. the current drawn by the backlight (and therefore the current drawn by the meter) can be reduced by installing a 1/4 watt resistor between pins 3 and 9. the brightness of the meter will be reduced proportionately. 9v-powered backlit models function with supply voltages up to +14v, however, activating the backlight with voltages greater than 9.2v can damage the meter. therefore, a 1/4 watt series resistor must be installed between pins 3 and 9 in these situations. the value of the series resistor is determined using the following formula:

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4 DMS-20lcd 3? digit, lcd display digital panel voltmeters r2 r1 + r2 x v in = reading 50k ? < r1 + r2 < 10m ? 4. floating signal source measurements: floating signals can be measured using the circuits shown in figures 5 and 6. figure 5 uses a 5v-powered meter. figure 6 uses a 9v-powered meter. connecting pin 10 (analog common) to (C) input lo (pin 12) provides the reference point for the meter's input. a "floating" input is a signal that has no galvanic connection to the meter's power supply. in the figures below, the 1.5v battery illustrates a true floating input. figure 3. differential input configuration (5v-powered models) 5. process control (4-to-20ma) measurements: in many common process-control applications, a 4-to-20ma current loop is used to transmit information. because DMS-20lcd meters have such high input impedance, a simple shunt resistor across the meter's input can be used to convert the loop current to a voltage. see figure 7. the value of the shunt resistor is a figure 6. floating input measurements (9v-powered models) figure 5. floating input measurements (5v-powered models) figure 4. input attenuation circuit applications 2. differential input configurations: differential measurements can be made with either 5v-powered or 9v-powered meters. figure 3, though not a practical real-world application, uses a voltage divider to demonstrate the concept of a differential input signal. be careful not to exceed the 2v common mode voltage limitation for 5v powered meters. 3. engineering scaling: for measuring voltages greater than the full scale input range of a given meter, the input signal must be attenuated. a simple voltage divider (similar to that shown in figure 4) will scale the input to within the range of the selected meter. r1 and r2 should be precision, 1%, metal-film resistors with absolute tcr's less than 50ppm/c. see ap note 4 for more information on engineering scaling.

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5 3? digit, lcd display digital panel voltmeters DMS-20lcd to calibrate the circuit of figure 7, perform the following: 1. with 4ma applied, adjust the 50k ? potentiometer (r2) to display a reading of "000" (assuming that is the desired reading). 2. with 20ma applied, adjust the gain-adjust potentiometer on the back of the meter to display a reading of "1999". for different full scale readings, alter the value of r shunt accordingly. r shunt = r1 = v fsr /i fsr where: v fsr = full scale reading (in volts) i fsr = relative full scale current (in amps) example: for a meter with a 2v full scale input (1.999 full scale reading) and a desired full scale display reading of 1000 (with an input of 20ma), v fsr = 1.000 volts r shunt = 1.000v/(0.020 C 0.004)a r shunt = 1.000v/0.016a = 62.5 ohms function of the scaling requirements of the particular application and can be calculated using the following equation: figure 7. 4-to-20ma current loop operation (5v-powered models) r2 (r1 + r2 + r3) = 0.1 6. power supply monitoring: a popular application for datel's low-power lcd meters is monitoring the supply voltage in battery- operated portable equipment. figure 8 demonstrates how a 9v- powered DMS-20lcd can be used to monitor its own supply. the meter used is the DMS-20lcd-1-9. a three-resistor voltage divider is used to attenuate the battery voltage and also to satisfy the requirement that the input voltages applied to pins 12 and 11 be at least 1.5 volts above and below the battery voltage applied to pins 1 (+battery) and 3 (Cbattery). the divider should be designed so that 1/10th the battery voltage falls across the inputs to the meter: therefore, the 9v battery voltage appears to the meter inputs as 0.9v. with the decimal point moved to its dp2 position (pin 5 tied to pin 3), the meter reads 9.00 volts. the circuit can be calibrated by first measuring the actual battery voltage with another meter and then adjusting the gain- adjust potentiometer on the back of the DMS-20lcd until a similar reading is obtained. if possible, the resistors in the divider should be 1% metal-film types with tcr's less than 50ppm/c. 7. external gain adjustment: connect reference out (pin 8) to reference in (pin 7) for normal, factory calibrated, operation. use the circuit shown in figure 9 for applications needing external gain adjustment. calibration is performed with a precise, near-full-scale, input voltage. figure 9. external gain adjustment figure 8. power supply monitor (9v-powered models) applications ! " # " #
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1 12 3 +bat (C) in lo Cbat 11 (+) in hi 5 dp2 DMS-20lcd-1-9 r2 r1 r3 45.3k 10.1k 45.3k 9v battery + C 8 7 ref out ref in 12 voltage calibrator out 10 (+) in hi (C) in lo ana comm = 10 to 20 turns 7 ref in 11 732, 1% 8.06k, 1% 5v ret/ Cbat in connections for 2v, 20v and 200v model s connections for 200mv models com 1 +5v in/ +bat in 17.4k, 1% 2k 24.3k, 1% 3 12 DMS-20lcd for +5v models, tie (C) in lo to pin 3. for +9v models, tie (C) in lo to pin 10 8 nc 200
datel, inc. 11 cabot boulevard, mansfield, ma 02048-1151 tel: (508) 339-3000 (800) 233-2765 fax: (508) 339-6356 internet: www.datel.com email: sales@datel.com data sheet fax back: (508) 261-2857 datel (uk) ltd. tadley, england tel: (01256)-880444 datel s.a.r.l. montigny le bretonneux, france tel: 01-34-60-01-01 datel gmbh mnchen, germany tel: 89-544334-0 datel kk tokyo, japan tel: 3-3779-1031, osaka tel: 6-354-2025 datel makes no representation that the use of its products in the circuits described herein, or the use of other technical info rmation contained herein, will not infringe upon existing or future patent rights. the descriptions contained herein do not imply the granting of licenses to make, use, or sell equipment constructed in accordance therewith. specifications are s ubject to change without notice. the datel logo is a registered datel, inc. trademark. ?? iso 9001 iso 9001 registered ds-0291c 01/02 DMS-20lcd 3? digit, lcd display digital panel voltmeters mechanical specifications mechanical dimensions: inches (mm) tolerances: 2 pl dec 0.02 (0.51) 3 pl dec 0.010 (0.254) lead dimensions: 0.025 (0.635) x 0.025 (0.635) nominal recommended pc board finished hole diameter: 0.042 0.003 (1.067 0.076) made in usa DMS-20lcd-x-xx front view dp1 dp2 dp3 pin #1 identifier +5v supply/ +battery n.c. 5v return/ Cbattery dp3 dp2 dp1 1 2 3 4 5 6 (C) input lo (+) input hi analog common n.c./backlight reference out reference in 12 11 10 9 8 7 0.80 (20.3) 0.15 (3.8) typ. 0.50 (12.7) 0.10 (2.5) typ. 0.040 (1.02) 0.040 (1.02) 1.10 (27.9) 0.10 (2.5) typ. 0.25 (6.4) typ. 0.425 (10.80) 0.040 (1.02) 1.30 (33.0) 1.38 (35.1) 0.88 (22.3) ? ? 0.160 (4.06) 0.160 (4.06) pin 1 calibration potentiometer hole location 0.125 (3.175) diameter (use only when pc board mounting)

#2-56 insert 0.156 (3.96) deep front view 1.280 (32.51) 0.187 (4.75) optional bezel (dms-bzl3 and dms-bzl4) recommended drill and panel cutout dimensions 1.826 (46.38) 0.838 (21.29) 1.336 (33.93) 1.626 (41.30) 1.07 (27.18) internal corner radii: 0.032 (0.81) max. 0.145 (3.68) 0.093 (2.362) diameter (4 required) only when using optional bezel assembly 0.116 (2.95)

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