3

3 ½

DIGIT , LED

DISPLA Y

DIGIT AL

P ANEL V O L TMETERS

DMS-30PC

Applications

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

measurements 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 flow in the wiring that connects

unstable readings.

Figure 2. Single-Ended Input Configuration

DMS-30PC meters are highly versatile devices that can be used in

hundreds of applications. The application circuits chosen for this

section 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 straightforward 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-voltage 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).

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.

DMS-30PC-X-BS

+0.3V max.

18mA max.

All Others

+0.4V max.

6mA max.

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

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

recommend, 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 water-soluble solders and thorough cleaning

procedures.

8. 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

1

12

3

+5V SUP

(–) IN LO

5V RET

DATEL

UPA-5/500

120 VAC

11

(+) IN HI

6

DP1

+

–

AC to DC Converter

DMS-30PC-1

8

7

REF OUT

REF IN