1. Single-Ended Input Confi gurations: True single-ended measure-
ments can be made with any DMS-30PC meter. 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). This will ensure that large LED currents will not
fl ow in the wiring that connects V
IN to (–) INPUT LO (pin 12). Ground-
loop currents can cause unstable readings.
Figure 2. Single-Ended Input Confi guration
DMS-30PC meters are highly versatile devices that can be used in
hundreds of applications. The application circuits chosen for this sec-
tion have historically received many inquiries. Every attempt has been
made to ensure technical accuracy, and all of the following circuits
have been prototyped and tested to ensure functionality. Please keep
in mind, however, that real-world applications are seldom as straight-
forward as the approaches presented here. Most applications have
many more components — and many more connections — than the
illustrations show.
The simplifi ed schematic shown in Figure 1 can be very useful when
debugging a malfunctioning panel meter circuit, particularly if the
user has some knowledge of operational amplifi ers (op amps). The
meter's high-impedance input consists of an op amp powered from a
±5Vdc power supply (the –5V is internally generated). Knowing this,
one can easily see why input signals applied to (–) INPUT LO and (+)
INPUT HI have to be kept within the power supply rails of ±5V. Also
note that only pin 11 has a current-limiting 909kΩ series resis-
tor. High input voltages that have a common ground with pin 3 (5V
RETURN) should only be applied to pin 11 ((+) INPUT HI) and never to
pin 12. In these high-voltage cases, pin 12 should always be tied to
pin 3 (5V RETURN).
One of the simplifi ed schematic's noteworthy features is that it
shows internal voltage values. It also shows that pin 3 is the meter's
zero-volt reference point — regardless of the type of power or signal
source used. This is an important point to keep in mind when a digital
or analog multimeter is used to make system measurements. The
multimeter's negative lead (usually the black one) must be connected
to pin 3 (5V RETURN).
4. DISPLAY TEST (Pin 2): Connecting pin 2 to +5V SUPPLY (pin 1) will
activate all LED segments, except the decimal points, and the display
will read "1888" regardless of the actual applied input. If a negative
input is applied, DISPLAY TEST will also activate the minus sign. To
protect the LED's, the display should not be left in the "test" mode for
more than 10 seconds.
5. 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 desired decimal point by tying the
appropriate pin (pin 4, 5 or 6) to pin 3 (5V RETURN). Unused decimal
point location pins should be left open.
Hard wiring is preferable, however, you can use logic gates to
exercise dynamic control over the location of the decimal point if the
following drive conditions are met:
Model Applied "0" Voltage Load Current*
DMS-30PC-X-RL +0.05V max. 0.7mA max.
All Others +0.4V max. 6mA max.
* The driving gates must be able to sink this much current
(I
OL) with a logic "0" output.
6. Gain Adjust: There is a gain-adjust potentiometer on the back of
each meter. It has approximately ±50 counts (±2.5%) 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. The circuit shown in Figure 10 provides ±10% range of
adjustment.
7. Soldering Methods: All models in the DMS-30PC 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.
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
1
12
3
+5V SUP
(–) IN LO
5V RET
11
(+) IN HI
6
DP1
+
–
AC to DC Converter
V
IN
DMS-30PC-1
8
7
REF OUT
REF IN
85-264Vac
DMS-30PC Series
3½ Digit, LED Display Low-Power,
Miniature Digital Panel Voltmeters
MPM_DMS_30PC.F05 Page 3 of 6
Technical enquiries email: sales@murata-ps.com, tel: +1 508 339 3000www.murata-ps.com/dpm
APPLICATIONS
