DMS-20LCD Series
3½ Digit, LCD Display Digital Panel Voltmeters
www.murata-ps.com/dpm
email: sales@murata-ps.com
05 Apr 2011 MPM_DMS20LCD.B08 Page 3 of 6
APPLICATIONS
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.
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, (–)
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 confi gurations.
1. Single-Ended Input Confi gurations: True single-ended measure-
ments 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 (–)
INPUT LO (pin 12).
8. Suggested Mating Connectors:
Panel mounted:
Connector housing DATEL P/N 4320-01069-0
Terminal type DATEL P/N 4400-01032-0
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 4320-01074-0
Figure 2. Single-Ended Input Confi guration
(5V-Powered Models)
RSeries = Ohms
+12.6 – 9.2V
0.035
Example: If +BATTERY (pin 1 with respect to pin 3) is +12.6V,
+BATTERY – 9.2V
0.035
R
Series = Ohms
RSeries = 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 +3.7V, or when the supply voltage for
9V-powered models falls below approximately 7.2V. However, the low-
battery annunciator’s turn-on threshold can vary signifi cantly from unit-
to-unit: as low as 2.7V for 5V-powered meters, and as low as 5.4V for
9V-powered models. Applications that use the LOW BAT annunciator
must be fully tested by the user, using a combination of low supply volt-
ages and the input signal’s minimum and maximum levels, to ensure
that all display readings are valid as long as the LOW BAT annunciator
remains off.
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 recom-
mend, 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 no-clean solders.
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 back-
light (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:
1
12
3
+5V SUP
(–) IN LO
5V RET
120 VAC
11
(+) IN HI
6
DP1
+
–
AC to DC Converter
V
IN
DMS-20LCD-1-5
7
REF OUT
REF IN
8
