the oem33 (also known as the vk1000) is one of the world's smallest digital voltmeters. it is an ideal replacement for analogue meters with advantages of accuracy, size and easy mounting. the module includes an a/d converter, lcd display of 10mm character height, and plastic housing with standard dual in line pin terminals for easy insertion into sockets or pc board. description operating temperature 0 to 50 o c storage temperature -20 to 70 o c operating relative humidity 80% operating specification ordering information dimensions mm features revision - 8 22/06/00 @@fbcreate 0001, oem33/h data sheet@@ oem33 & oem33h 3.5 di g it lcd di g ital voltmeter 3.5 digit 10mm character height lcd 200mv full scale sensitivity automatic zeroing and polarity indication 11 selectable annunciators easy to use decimal point selection built in snap fastener display on hold option oem33h panel cut out 40.5 x 22.5 fastening clips accept panel thickness 0.9 to 3.2mm this module is a version of the oem33 featuring a digital display hold facility. for normal, continuous operation connect the 'hold 1' pin to the gd pin. to hold the present reading, connect 'hold 1' to vdd. do not leave this pin floating or it will drift in and out of hold mode. oem33h - version with display hold facility oem33 3.5 digit, 200mv lcd voltmeter oem33h 3.5 digit, 200mv lcd with display hold characteristic condition min typ max units supply voltage ( vdd) 9 volts 5 volts 7 4.5 9 5 10 6 v v supply current (idd) 9 volts 5 volts 100 2 500 3 m a ma full scale 199.9 mv input impedance 100 m w reference voltage 9 volts 100 mv overload voltage 20 v zero i/p reading 0 + 1 counts accuracy at fsd 9 volts 5 volts + 2 + 2 + 4 + 4 counts counts linearity 9 volts 5 volts + 1 + 1 + 2 + 2 counts counts resolution 100 v cmrr 70 db temp coefficient 100 150 ppm/ o c electrical characteristics t a =25 o c ? vdd positive supply terminal vss negative supply terminal for 9 volts operation gd negative supply terminal for 5 volts operation ih input high terminal il input low terminal rh reference high input terminal rl reference low input terminal hold1 connect to vdd for hold and gd for continuous c analogue common xbp for driving annunciator bp lcd back plane d1, d2, d3 decimal point pins . d1 = .000, d2 = 0.00 d3 = 00.0 the decimal point will appear if the corresponding terminal is connected to xbp. bat, o c, o f,~, m, m , m w , k w , v, a, hold2 annunciators pin functions all annunciators not in use must be connected to the bp pin for suppression purposes. to light up an annunciator, connect the corresponding pin to xbp. di g ital panel modules user g uide
dqghuv hohfwurqlfv sof bayham place, london nw1 oeu uk tel: +44 ( 0 ) 20 7380 8167 fax: +44 ( 0 ) 20 7874 1908 http://www.meters.anders.co.uk for 9v operation it is recommended to power from a 9v battery. the inputs are intended to float with respect to the supply but if they do not float they must be no closer than 1.5v from either vdd or vss (vdd-1.5v and vss+1.5v) see the circuits for non-floating inputs below. connection diagram basic configuration application circuits to measure voltages greater than 200mv an attenuator is required. v in =v d x r1+r2 v d max. is 199.99mv examples v in display v d r1 r2 2v 1.999v 199.9mv 1m w 110k w 10v 1500rpm 150mv 1m w 15k w r2 the input impedance becomes r1+r2. choose accurate stable resistors. typically, r1=1m w. 9m w is a practical upper limit. dc multi-range voltage measurement dc current measurement shunt resistance r s = v s w it is important to note the power dissipation in the shunt and choose resistor rating accordingly p s = vs = i in r s w examples 2 2 i in i in current r s p s 200mv 1 w 0.04w 2a 0.1 w 0.4w dc multi-range current measurement for multi-range, use, a 2 pole, 5 way rotary switch. 1 pole for range select and the other to connect the appropriate decimal point to xbp dc voltage ratio measurement to determine the ratio between two voltages apply the inputs as shown. displayed reading = v2 x 1000 over range occurs when v2 > 2 note jumper j1 must be closed v1 v1 to achieve a zero display reading for a non-zero voltage input, apply the offset voltage between c and il. for a positive offset apply a positive signal to il w.r.t. c. apply the input signal between ih and c note jumper j1 must be open dc voltage offset the oem33 is designed for 5/9v supply. incorrect supply polarity will destroy the module immediately. it is ready for general use when connected as in fig 1 for 5 volts. for 9 volt supply the module may need calibrating before use as follows. connect as in fig. 2, apply 100mv to the inputs from a calibrated source and adjust vr1 until the display reads 1000. the input range is 0-199.9mv . over-range is indicated by blanking the three least significant digits and displaying a "1" in the most significant digit. if the input voltage is reversed, a minus sign is displayed automatically. the module has 3 decimal points. d1, d2, d3 and 11 selectable annnunciators. for 5v operation, il must be connected to gd for non-floating inputs (as fig. 1) and to the analogue user instructions where a single 5v supply is not suitable but you must connect your input signal ground to the module supply ground then either of the two non-floating input circuits can be used. note that the module is set in 9v supply mode but jumper j1 is left open. non floating inputs (a) non floating i nputs (b) using the formulae choose resistors to ensure the analogue inputs are no closer than 1.5v from either vdd or vss (vdd-1.5v or vss+1.5v) for multi-range, use a 2 pole, 4 way rotary switch. 1 pole for range select and the other to connect the appropriate decimal point to xbp. dc voltage measurement
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