DMS-40LCD Series
4�½ Digit, LCD Display Digital Panel Voltmeters
3. Low Battery Annunciator:
The “BAT” 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.
4. HOLD/BACKLIGHT (Pin 9) Function:
For non-backlit models, con-
necting pin 9 (HOLD/BACKLIGHT) to pin 3 (5V RETURN/
–BATTERY) will hold (continuously display) the last reading.
If not used, pin 9 should be left open for these models.
For backlit models, grounding pin 9 (i.e. connecting it to pin 3) turns on
the backlighting LED’s. 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:
+BATTERY – 9.2V
0.035
Example: If +BATTERY (pin 1 with respect to pin 3) is +12.6V,
R
Series
=
+12.6 – 9.2V
0.035
R
Series
= 97 Ohms
In any backlit application, including those with supply voltages
< 9.2V, 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 backlight will be reduced
proportionately.
5. ANALOG COMMON (Pin 10):
This pin is connected to an internal,
low-noise, “relative” ground. It is used in certain “floating” measure-
ments 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.
6. REFERENCE IN/OUT (Pin 7):
This pin accesses the meter’s internal
reference and is used during the factory calibration procedure. Pin 7
should be left open in most common applications. It can be used in
certain “ratiometric” applications in which it is desireable for the meter’s
reference to track an external reference. See the Applications section
of the DATEL Panel Meter Catalog for more details.
7. Gain Adjust:
There is a gain-adjust potentiometer on the back of each
meter. It has approximately ±150 counts of adjustment range. 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.
Ohms
8. Soldering Methods:
All models in the DMS-40LCD Series easily
withstand most common wave soldering operations. We recommend,
however, 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.
9. 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
R
Series
=
Ohms
APPLICATIONS
DMS-40LCD 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 configurations.
1. Single-Ended Input Configurations:
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).
DMS-40LCD-0/1-5
11
(+) IN HI
+
V
IN
–
12
(–) IN LO
1
+5V SUP
2
RANGE
6
DP1
3
5V RET
120 VAC
DATEL
UPA-5/500
AC to DC Converter
Figure 2. Single-Ended Input Configuration
(5V-Powered Models)
www.murata-ps.com
Technical enquiries
email: sales@murata-ps.com, tel:
+1 508 339 3000
MPM_DMS40LCD.C02
Page 3 of 6
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