1. Single-Ended Input Configurations: True single-ended measure-

ments can be made with any DMS-30DR 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

flow in the wiring that connects VIN to (–) INPUT LO (pin 12). Ground-

loop currents can cause unstable readings.

Figure 2. Single-Ended Input Configuration

DMS-30DR 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 simplified 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 amplifiers (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 909k

Ω series resistor. 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-volt-

age cases, pin 12 should always be tied to pin 3 (5V RETURN).

One of the simplified 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).

1

12

3

+5V SUP

(–) IN LO

5V RET

11

(+) IN HI

6

DP1

+

–

AC to DC Converter

VIN

DMS-30DR-1

8

7

REF OUT

REF IN

85-264Vac

www.murata-ps.com/support

DMS-30DR Series

Sunlight Readable, 3½ Digit Panel Meters

with Auto-Dimming LED Displays

MPM_DMS-30DR.C0

3 Page 3 of 6

APPLICATIONS

accuracy and temperature drift of the meter. A ±1% 1.82K limiting

resistor is connected between the reference IC and pin 9.

4. ANALOG COMMON (Pin 10): This pin is connected to an internal,

low-noise, “relative” ground. Pin 10 also serves as the internal

ground for the +1.225V reference IC. ANALOG COMMON is used

in certain differential and “floating” measurements as described in

the Applications section of this data sheet, and in DMS Applica-

tion Note 3. For the vast majority of applications, pin 10 should not

be connected to pin 3 (5V RETURN), or to your system’s analog

ground.

5. REFERENCE OUTPUT (Pin 8) and INPUT (Pin 7): Pin 8 is a preci-

sion reference actively trimmed at the factory. For normal operation,

pin 8 must be tied to pin 7 to achieve all listed accuracy and drift

specifications.

6. 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 appro-

priate 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:

Applied “0” Voltage: +0.4V max

Drive Current*: 6mA max.

* The driving gates must be able to sink this much current (IOL)

with a logic “0” output.

7. Gain-Adjust Potentiometer: The gain-adjust potentiometer located

on the rear of the meter has approximately ±50 counts (±2.5%)

of adjustment range with a near full-scale input. Since these

meters essentially have no zero/offset errors, a gain adjustment is

effectively an overall accuracy adjustment. Though they may be

performed at any input level except zero, accuracy adjustments are

most effective when performed with half-scale (or higher) positive

input signals.

If a wider adjustment range is required, an external potentiometer

circuit can be configured using the meter’s +1.225V reference

output (pin 9). The circuit shown in Figure 9 provides ±10% range

of adjustment.

8. Soldering Methods: All models in the DMS-30DR Series easily

withstand most common leaded or lead-free soldering opera-

tions, performed either manually or by wave soldering machines.

However, users should evaluate the effects their particular soldering

techniques may have on the meter’s plastic case and precision

electrical performance. We highly recommend using low residue,

no-clean solders.

9. Suggested Mating Connectors:

Panel mounted: Connector housing P/N 4320-01069-0

Terminal type: P/N 4400-01032-0

Crimping tool: 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: P/N 4320-01074-0